2,954 research outputs found

    A case of silent invasion : citizen science confirms the presence of Harmonia axyridis (Coleoptera, Coccinellidae) in Central America

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    Harmonia axyridis (Coleoptera, Coccinellidae) is a globally invasive ladybird. It has been intentionally introduced in many countries as a biological control agent, whereas it has been unintentionally released in many others. Climatic factors are important in limiting the spread of H. axyridis. For example, very few records are known from tropical or desert regions. Currently, no published reports are known from Central America. Here, we report H. axyridis from Costa Rica, Guatemala, Honduras, Panama, and Puerto Rico. Specimens were either observed by the authors, discovered in dried insect collections, or retrieved from searching through online photographs available from the citizen science project iNaturalist and the photo-sharing website Flickr. These new records and the wide distribution of H. axyridis in Latin America suggest several invasion events, which have gone unnoticed until now. We stress the need for further, large-scale monitoring and show the advantage of citizen science to assess the presence of invasive alien species

    Self-optimized construction of transition rate matrices from accelerated atomistic simulations with Bayesian uncertainty quantification

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    A massively parallel method to build large transition rate matrices from temperature accelerated molecular dynamics trajectories is presented. Bayesian Markov model analysis is used to estimate the expected residence time in the known state space, providing crucial uncertainty quantification for higher scale simulation schemes such as kinetic Monte Carlo or cluster dynamics. The estimators are additionally used to optimize where exploration is performed and the degree of temperature ac- celeration on the fly, giving an autonomous, optimal procedure to explore the state space of complex systems. The method is tested against exactly solvable models and used to explore the dynamics of C15 interstitial defects in iron. Our uncertainty quantification scheme allows for accurate modeling of the evolution of these defects over timescales of several seconds.Comment: 14 pages, 7 figure

    Principal infinity-bundles - Presentations

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    We discuss two aspects of the presentation of the theory of principal infinity-bundles in an infinity-topos, introduced in [NSSa], in terms of categories of simplicial (pre)sheaves. First we show that over a cohesive site C and for G a presheaf of simplicial groups which is C-acyclic, G-principal infinity-bundles over any object in the infinity-topos over C are classified by hyper-Cech-cohomology with coefficients in G. Then we show that over a site C with enough points, principal infinity-bundles in the infinity-topos are presented by ordinary simplicial bundles in the sheaf topos that satisfy principality by stalkwise weak equivalences. Finally we discuss explicit details of these presentations for the discrete site (in discrete infinity-groupoids) and the smooth site (in smooth infinity-groupoids, generalizing Lie groupoids and differentiable stacks). In the companion article [NSSc] we use these presentations for constructing classes of examples of (twisted) principal infinity-bundles and for the discussion of various applications.Comment: 55 page

    Autumn Foods of White-Tailed Deer in Arkansas

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    Rumen contents from 65 hunter-harvested deer were collected and analyzed during 1985-86 to estimate the principal autumn foods consumed by white-tailed deer inhabiting the Ozark Mountains, Arkansas River Valley, and Gulf Coastal Plain regions of Arkansas. Deer in the Ozarks and Coastal Plain fed heavily on woody browse species, which comprised 99% of rumina identified from these 2 regions. Acorns were the primary food of deer in these heavily forested areas. Acorns and other woody browse were less important to deer inhabiting the Arkansas River Valley. In this region of interspersed agricultural fields and bottomland forests, soybeans and corn comprised 75% of the diet, and acorns accounted for only 2%

    Advanced composite airframe program: Today's technology

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    The Advanced Composite Airframe Program (ACAP) was undertaken to demonstrate the advantages of the application of advanced composite materials and structural design concepts to the airframe structure on helicopters designed to stringent military requirements. The primary goals of the program were the reduction of airframe production costs and airframe weight by 17 and 22 percent respectively. The ACAP effort consisted of a preliminary design phase, detail design, and design support testing, full-scale fabrication, laboratory testing, and a ground/flight test demonstration. Since the completion of the flight test demonstration programs follow-on efforts were initiated to more fully evaluate a variety of military characteristics of the composite airframe structures developed under the original ACAP advanced development contracts. An overview of the ACAP program is provided and some of the design features, design support testing, manufacturing approaches, and the results of the flight test evaluation, as well as, an overview of Militarization Test and Evaluation efforts are described

    The Galactic Contribution to IceCube's Astrophysical Neutrino Flux

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    High energy neutrinos have been detected by IceCube, but their origin remains a mystery. Determining the sources of this flux is a crucial first step towards multi-messenger studies. In this work we systematically compare two classes of sources with the data: Galactic and extragalactic. We assume that the neutrino sources are distributed according to a class of Galactic models. We build a likelihood function on an event by event basis including energy, event topology, absorption, and direction information. We present the probability that each high energy event with deposited energy Edep>60E_{\rm dep}>60 TeV in the HESE sample is Galactic, extragalactic, or background. For Galactic models considered the Galactic fraction of the astrophysical flux has a best fit value of 1.3%1.3\% and is <9.5%<9.5\% at 90\% CL. A zero Galactic flux is allowed at <1σ<1\sigma.Comment: Updated with 6 year HESE data from IceCube, accepted for publication in JCA

    1/m1/m Corrections for Orbitally Excited Heavy Mesons and the 1/21/2 - 3/23/2 Puzzle

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    We re-investigate the effects of the 1/mc1/m_c corrections on the spectrum of the lowest orbitally excited DD-meson states. We argue that one should expect the 1/mc1/m_c corrections to induce a significant mixing between the two lowest lying 1+1^+ states. We discuss the implications of this mixing and compute its effect on the semileptonic decays BDνˉB \to D^{**} \ell \bar{\nu} and the strong DD^{**} decays.Comment: 9 pages, 3 figure

    Objective measures for predicting the intelligibility of spectrally smoothed speech with artificial excitation

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    A study is presented on how well objective measures of speech quality and intelligibility can predict the subjective in- telligibility of speech that has undergone spectral envelope smoothing and simplification of its excitation. Speech modi- fications are made by resynthesising speech that has been spec- trally smoothed. Objective measures are applied to the mod- ified speech and include measures of speech quality, signal- to-noise ratio and intelligibility, as well as proposing the nor- malised frequency-weighted spectral distortion (NFD) measure. The measures are compared to subjective intelligibility scores where it is found that several have high correlation (|r| ≥ 0.7), with NFD achieving the highest correlation (r = −0.81

    Exploratory study into a safety format for composite columns exposed to fire

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    Current performance based structural fire engineering approaches evaluate structural behaviour under prescribed fire scenarios. The mechanical properties of the materials, the load conditions and geometric parameters are all however fraught with uncertainty, and there is currently no clear safety format ensuring the reliability of the design solution. In this contribution, a safety format is explored for evaluating the fire resistance of composite columns, following results obtained in earlier studies on uncertainty quantification. Using the safety format, a single nonlinear finite element evaluation of the fire resistance time is combined with a global safety factor, defining its design value. Under the assumptions derived from earlier work, the safety format works well, but additional parameter studies indicate that good performance is limited to relatively low ambient design utilization ratios. The results thus highlight the importance of uncertainty quantification and the limitations of basing a safety format for structural fire design on limited studies. It is concluded that detailed studies into the probabilistic description of the response of composite columns exposed to fire are required to generalize the results to a broadly applicable design rule
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