86 research outputs found
Evidence for Rapoport's rule and latitudinal patterns in the global distribution and diversity of alien bird species
Aim To quantify global latitudinal patterns in the distributions of alien bird species to assess whether these species conform to Rapoport's rule (i.e. show a positive latitudinal gradient in latitudinal range extent), and to test whether where species are introduced, and where species fail to establish, may help to drive observed patterns. Location Global. Taxon Birds (group Aves). Methods Data on locations of introduction and establishment for 355 species with established alien populations were combined with data on native range extents (measured in 5 degrees bands of latitude). Relationships between (a) latitude and introduced and established alien species richness, and (b) latitude and introduced and established alien range extent, were plotted. Linear regressions and paired t-tests were used to compare latitudinal range extents, midpoints, and limits of each species in its introduced alien range, established alien range and native range. Results Latitudes that have more established alien bird species also have had more species introduced in total. The mean total latitudinal extents (i.e. geographic range size) of established alien bird species increase with latitude poleward of the tropics, consistent with Rapoport's rule, but are smaller in the tropics. This pattern is weaker in the range sizes of native bird species. Alien bird species are more likely to be introduced within the latitudinal confines of their native ranges, and are more likely to contract away from the more extreme latitudes to which they were introduced. Alien bird species are in general more likely to have established populations nearer the equator. Main conclusions Including data on locations of introduction in addition to established distributions enables us to determine the extent to which large-scale alien species distributions are determined by anthropogenic or natural processes. Latitudinal patterns in range extent (Rapoport's rule) and species richness in alien birds are largely a consequence of where species have been introduced, and hence are unlikely to be informative of equivalent patterns in native species
2015 ACVIM Small Animal Consensus Statement on Seizure Management in Dogs
This report represents a scientific and working clinical consensus statement on seizure management in dogs based on current literature and clinical expertise. The goal was to establish guidelines for a predetermined, concise, and logical sequential approach to chronic seizure management starting with seizure identification and diagnosis (not included in this report), reviewing decisionâmaking, treatment strategies, focusing on issues related to chronic antiepileptic drug treatment response and monitoring, and guidelines to enhance patient response and quality of life. Ultimately, we hope to provide a foundation for ongoing and future clinical epilepsy research in veterinary medicine
Search for a scalar or vector particle decaying into Zgamma in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for a narrow scalar or vector resonance decaying into
Zgamma with a subsequent Z decay into a pair of electrons or muons. The data
for this search were collected with the D0 detector at the Fermilab Tevatron
ppbar collider at a center of mass energy sqrt(s) = 1.96 TeV. Using 1.1 (1.0)
fb-1 of data, we observe 49 (50) candidate events in the electron (muon)
channel, in good agreement with the standard model prediction. From the
combination of both channels, we derive 95% C.L. upper limits on the cross
section times branching fraction (sigma x B) into Zgamma. These limits range
from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/c^2 to 2.5
(3.1) pb for a mass of 140 GeV/c^2.Comment: Published by Phys. Lett.
Human Resource Flexibility as a Mediating Variable Between High Performance Work Systems and Performance
Much of the human resource management literature has demonstrated the impact of high performance
work systems (HPWS) on organizational performance. A new generation of studies is
emerging in this literature that recommends the inclusion of mediating variables between HPWS
and organizational performance. The increasing rate of dynamism in competitive environments
suggests that measures of employee adaptability should be included as a mechanism that may
explain the relevance of HPWS to firm competitiveness. On a sample of 226 Spanish firms, the
studyâs results confirm that HPWS influences performance through its impact on the firmâs
human resource (HR) flexibility
Case-based learning: Predictive features in indexing
Interest in psychological experimentation from the Artificial Intelligence community often takes the form of rigorous post-hoc evaluation of completed computer models. Through an example of our own collaborative research, we advocate a different view of how psychology and AI may be mutually relevant, and propose an integrated approach to the study of learning in humans and machines. We begin with the problem of learning appropriate indices for storing and retrieving information from memory. From a planning task perspective, the most useful indices may be those that predict potential problems and access relevant plans in memory, improving the planner's ability to predict and avoid planning failures. This âpredictive featuresâ hypothesis is then supported as a psychological claim, with results showing that such features offer an advantage in terms of the selectivity of reminding because they more distinctively characterize planning situations where differing plans are appropriate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46928/1/10994_2004_Article_BF00993173.pd
Search for single top quark production in ppbar collisions at sqrt(s)=1.96 TeV
We present a search for electroweak production of single top quarks in the
s-channel and t-channel using neural networks for signal-background separation.
We have analyzed 230 pb of data collected with the D0 detector at the
Fermilab Tevatron Collider at a center-of-mass energy of 1.96 TeV and find no
evidence for a single top quark signal. The resulting 95% confidence level
upper limits on the single top quark production cross sections are 6.4 pb in
the s-channel and 5.0 pb in the t-channel.Comment: 9 pages, 4 figure
Measurement of the differential cross section for the production of an isolated photon with associated jet in ppbar collisions at sqrt(s)=1.96 TeV
The process ppbar -> photon + jet + X is studied using 1.0 fb^-1 of data
collected by the D0 detector at the Fermilab Tevatron ppbar collider at a
center-of-mass energy sqrt(s)=1.96 TeV. Photons are reconstructed in the
central rapidity region |y_gamma|<1.0 with transverse momenta in the range
30<Pt_gamma<400 GeV while jets are reconstructed in either the central
|y_jet|15 GeV.
The differential cross section d^3sigma/dPt_gamma dy_gamma dy_jet is measured
as a function of Pt_gamma in four regions, differing by the relative
orientations of the photon and the jet in rapidity. Ratios between the
differential cross sections in each region are also presented. Next-to-leading
order QCD predictions using different parameterizations of parton distribution
functions and theoretical scale choices are compared to the data. The
predictions do not simultaneously describe the measured normalization and
Pt_gamma dependence of the cross section in any of the four measured regions.Comment: 13 pages, 10 figure
Measurement of the ttbar production cross section and top quark mass extraction using dilepton events in ppbar collisions
We present a measurement of the top quark pair production cross section in
ppbar collisions at \sqrt{s}=1.96 TeV using approximately 1 fb^{-1} of data
collected with the D0 detector. We consider decay channels containing two high
pt charged leptons where one lepton is identified as an electron or a muon
while the other lepton can be an electron, a muon or a hadronically decaying
tau lepton. For a mass of the top quark of 170 GeV, the measured cross section
is 7.5 +1.0-1.0 (stat) +0.7-0.6 (syst) +0.6-0.5 (lumi) pb. Using lepton+tau
events only, we measure: \sigma_ttbar \times B(ttbar to ltau bbbar) = 0.13
+0.09-0.08 (stat) +0.06-0.06 (syst) +0.02-0.02 (lumi) pb. Comparing the
measured cross section as a function of the mass of the top quark with a
partial next-to-next-to leading order Quantum Chromodynamics theoretical
prediction, we extract a mass of the top quark of 171.5 +9.9-8.8 GeV, in
agreement with direct measurements.Comment: published in Phys. Lett. B, 10 pages, 7 figure
No saturation in the accumulation of alien species worldwide
Although research on human-mediated exchanges of species has substantially intensified during the last centuries, we know surprisingly little about temporal dynamics of alien species accumulations across regions and taxa. Using a novel database of 45,813 first records of 16,926 established alien species, we show that the annual rate of first records worldwide has
increased during the last 200 years, with 37% of all first records reported most recently (1970â2014). Inter-continental and inter-taxonomic variation can be largely attributed to the diaspora of European settlers in the nineteenth century and to the acceleration in trade in the twentieth century. For all taxonomic groups, the increase in numbers of alien species does not
show any sign of saturation and most taxa even show increases in the rate of first records over time. This highlights that past efforts to mitigate invasions have not been effective enough to keep up with increasing globalization
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