59 research outputs found
Contain or eradicate? Optimizing the management goal for Australian acacia invasions in the face of uncertainty
Aim To identify whether eradication or containment is expected to be the most cost-effective management goal for an isolated invasive population when knowledge about the current extent is uncertain.
Location Global and South Africa.
Methods We developed a decision analysis framework to analyse the best management goal for an invasive species population (eradication, containment or take no action) when knowledge about the current extent is uncertain. We used value of information analysis to identify when investment in learning about the extent will improve this decision-making and tested the sensitivity of the conclusions to different parameters (e.g. spread rate, maximum extent, and
management efficacy and cost). The model was applied to Acacia paradoxa DC, an Australian shrub with an estimated invasive extent of 310 ha on Table Mountain, South Africa.
Results Under the parameters used, attempting eradication is cost-effective for
infestations of up to 777 ha. However, if the invasion extent is poorly known, then attempting eradication is only cost-effective for infestations estimated as
296 ha or smaller. The value of learning is greatest (maximum of 8% saving) when infestation extent is poorly known and if it is close to the maximum extent for which attempting eradication is optimal. The optimal management action is most sensitive to the probability that the action succeeds (which depends on the extent), with the discount rate and cost of management also important, but spread rate less so. Over a 20-year time-horizon, attempting to eradicate
A. paradoxa from South Africa is predicted to cost on average ZAR 8 million if the extent is known, and if our current estimate is poor, ZAR 33.6 million as opposed to ZAR 32.8 million for attempting containment.
Main conclusions Our framework evaluates the cost-effectiveness of attempting eradication or containment of an invasive population that takes uncertainty in population extent into account. We show that incorporating uncertainty in the analysis avoids overly optimistic beliefs about the effectiveness of management enabling better management decisions. For A. paradoxa in South Africa,
attempting to eradicate is likely to be cost-effective, particularly if resources are
allocated to better understand and improve management efficacy.Centre of Excellence for Invasion Biolog
Search for Colour Reconnection Effects in e+e- -> W+W- -> hadrons through Particle-Flow Studies at LEP
A search for colour reconnection effects in hadronic decays of W pairs is
performed with the L3 detector at centre-of-mass energies between 189 and 209
GeV. The analysis is based on the study of the particle flow between jets
associated to the same W boson and between two different W bosons in qqqq
events. The ratio of particle yields in the different interjet regions is found
to be sensitive to colour reconnection effects implemented in some
hadronisation models. The data are compared to different models with and
without such effects. An extreme scenario of colour reconnection is ruled out
Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV
We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles
from a single W decay in good agreement with those from a light-quark Z decay
sample. We investigate their possible existence between particles coming from
different W's. No evidence for such inter-W BEC is found
Measurement of the Cross Section of W-boson pair production at LEP
The cross section of W-boson pair-production is measured with the L3 detector
at LEP. In a data sample corresponding to a total luminosity of 629.4/pb,
collected at centre-of-mass energies ranging from 189 to 209 GeV, 9834
four-fermion events with W bosons decaying into hadrons or leptons are
selected. The total cross section is measured with a precision of 1.4 % and
agrees with the Standard Model expectation. Assuming charged-lepton
universality, the branching fraction for hadronic W-boson decays is measured to
be: Br(W-->hadrons) = 67.50 +- 0.42 (stat.) +- 0.30(syst.) %, in agreement with
the Standard Model. Differential cross sections as a function of the W-
production angle are also measured for the semi-leptonic channels qqev and
qqmv
Studies of Hadronic Event Structure in e+e- Annihilation from 30 GeV to 209 GeV with the L3 Detector
In this Report, QCD results obtained from a study of hadronic event structure
in high energy e^+e^- interactions with the L3 detector are presented. The
operation of the LEP collider at many different collision energies from 91 GeV
to 209 GeV offers a unique opportunity to test QCD by measuring the energy
dependence of different observables. The main results concern the measurement
of the strong coupling constant, \alpha_s, from hadronic event shapes and the
study of effects of soft gluon coherence through charged particle multiplicity
and momentum distributions.Comment: To appear in Physics Report
Inclusive Sigma+ and Sigma0 Production in Hadronic Z Decays
We report on measurements of the inclusive production rate of Sigma+ and
Sigma0 baryons in hadronic Z decays collected with the L3 detector at LEP. The
Sigma+ baryons are detected through the decay Sigma+ -> p pi0, while the Sigma0
baryons are detected via the decay mode Sigma0 -> Lambda gamma. The average
numbers of Sigma+ and Sigma0 per hadronic Z decay are measured to be: <
N_Sigma+ > + = 0.114 +/- 0.011 (stat) +/- 0.009 (syst), <
N_Sigma0 > + = 0.095 +/- 0.015 (stat) +/- 0.013 (syst). These
rates are found to be higher than the predictions from Monte Carlo
hadronization models and analytical parameterizations of strange baryon
production
Measurement of the top quark mass in the ttâ dilepton channel from âs = 8 TeV ATLAS data
The top quark mass is measured in the ttÂŻ â dilepton channel (lepton = e,ÎŒ) using ATLAS data recorded in the year 2012 at the LHC. The data were taken at a proton proton centre-of-mass energy of âs = 8 TeV and correspond to an integrated luminosity of about 20.2 fbâ1. Exploiting the template method, and using the distribution of invariant masses of leptonâb-jet pairs, the top quark mass is measured to be mtop = 172.99±0.41 (stat) ±0.74 (syst) GeV, with a total uncertainty of 0.84 GeV. Finally, a combination with previous ATLAS mtop measurements from âs = 7 TeV data in the ttÂŻ â dilepton and ttÂŻ â lepton + jets channels results in mtop = 172.84±0.34 (stat)±0.61 (syst) GeV, with a total uncertainty of 0.70 GeV
Measurement of D*±, D± and Ds± meson production cross sections in pp collisions at âs=7 TeV with the ATLAS detector
The production of Dâ±, D± and D±s charmed mesons has been measured with the ATLAS detector in pp collisions at âs= 7 TeV at the LHC, using data corresponding to an integrated luminosity of 280 nbâ1. The charmed mesons have been reconstructed in the range of transverse momentum 3.5 <pT(D) <100 GeV and pseudorapidity |η(D)| <2.1. The differential cross sections as a function of transverse momentum and pseudorapidity were measured for Dâ± and D± production. The next-to-leading-order QCD predictions are consistent with the data in the visible kinematic region within the large theoretical uncertainties. Using the visible D cross sections and an extrapolation to the full kinematic phase space, the strangeness-suppression factor in charm fragmentation, the fraction of charged non-strange D mesons produced in a vector state, and the total cross section of charm production at âs= 7 TeV were derived
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