2,954 research outputs found
A case of silent invasion : citizen science confirms the presence of Harmonia axyridis (Coleoptera, Coccinellidae) in Central America
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
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
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
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
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
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 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 and is at 90\% CL. A zero Galactic flux is allowed at
.Comment: Updated with 6 year HESE data from IceCube, accepted for publication
in JCA
Corrections for Orbitally Excited Heavy Mesons and the - Puzzle
We re-investigate the effects of the corrections on the spectrum of
the lowest orbitally excited -meson states. We argue that one should expect
the corrections to induce a significant mixing between the two lowest
lying states. We discuss the implications of this mixing and compute its
effect on the semileptonic decays and the strong
decays.Comment: 9 pages, 3 figure
Objective measures for predicting the intelligibility of spectrally smoothed speech with artificial excitation
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
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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