580 research outputs found
The most vagile host as the main determinant of population connectivity in marine macroparasites
Although molecular ecology of macroparasites is still in its infancy, general patterns are beginning to emerge, e.g. that the most vagile host in a complex life cycle is the main determinantof the population genetic structure of their parasites. This insight stems from the observation that populations of parasites with only freshwater hosts are more structured than those with terrestrial or airborne hosts. Until now, the same has not been tested for marine systems, where, in theory, a fully marine life cycle might sustain high dispersal rates because of the absence of Obvious physical barriers in the sea. Here, we tested whether a marine trematode parasite that utilises migratory birds exhibited weaker population genetic structure than those whose life cycle utilises marine fish as the vagile host. Part of the mitochondrial cytochrome c oxidase 1 (COI) gene wassequenced from individual sporocysts from populations along the Atlantic coast of Europe and North Africa. Strong population structure (ÎŚ-ST = 0.25, p < 0.0001) was found in the fully marinetrematode Bucephalus minimus (hosted by fish), while no significant structure (ÎŚ-ST = 0.015, p = 0.19257) was detected in Gymnophallus choledochus (hosted by birds). However, demographicmodels indicate recent colonisation rather than high dispersal as an alternative explanation of the low levels of structure observed in G. choledochus. Our study is the first to identify significant genetic population structure in a marine autogenic parasite, suggesting that connectivity between populations of marine parasites can be limited despite the general potential for high dispersal of their hosts in the marine environment
Systematic reviews highlight the complex balance between good and harm from screening studies
Quantum-nondemolition criteria in traveling-wave second-harmonic generation
Using the full nonlinear equations of motion, we calculate the quantum-nondemolition (QND) correlations for the traveling-wave second-harmonic generation. We find that, after a short interaction length, these are qualitatively different from results calculated previously using a linearized fluctuation analysis. We demonstrate that, although individual QND criteria can be very good in certain regions, there is no region where all three of the standard criteria are perfect, as has previously been claimed. We also show that only the amplitude quadrature of the output field can be considered as a QND quantity, with the phase quadrature not satisfying all the criteria
Wear Mechanisms of Carbon-Based Refractory Materials in Silicomanganese Tap HolesâPart I: Equilibrium Calculations and Slag and Refractory Characterization
Silicomanganese (SiMn) as an alloy supplies silicon and manganese to the steelmaking industry.
It is produced through carbothermic reduction in a submerged arc furnace. The slag and metal
are typically tapped through a single-level tap hole at 50 K (50 C) below the process temperature
of 1873 K to 1923 K (1600 C to 1650 C). In one tapblock refractory design configuration,
the tap hole is installed as a carbon tapblock and rebuilt during the life of the lining
using carbon-based cold ramming paste. The carbon tapblock lasts for a number of years and
ramming paste only for months. The purpose of the study presented here was to determine to
what extent chemical reactions between carbon-based refractory and slag or metal in the tap
hole of a SiMn furnace can contribute to wear of tap-hole refractory. The results of the study
are reported in two parts. In Part I, the results of thermodynamic calculations of the potential
for chemical reaction between carbon-based refractory material and slag or metal are reported.
The results were tested experimentally using pure graphite and synthetic SiMn slag (produced
from pure oxides). The paper also reports the composition, microstructure, and phases of
industrial SiMn slag, and commercially available carbon block and cold ramming paste
refractory materials. These compositions were used in predicted equilibria of refractoryâslag
reactions. Thermodynamic calculations suggest that reaction between SiMn slag and carbonbased
tap-hole refractory is possible, and experiments with nominally pure materials support
this. However, practical refractory materials are by no means pure materials, and contain
secondary phases and porosity which can be expected to affect reaction with slag. Such reactions
are examined in Part II.National Research Foundation of South Africa (Grant TP2011070800005).http://link.springer.com/journal/116632016-04-30hb201
Homogenization and seismic assessment : review and recent trends
The mechanics of masonry structures has been for long
underdeveloped in comparison with other fields of knowledge. Presently,
non-linear analysis is a popular field in masonry research and
advanced computer codes are available for researchers and practitioners.
The chapter presents a discussion of masonry behaviour and
clarifies how to obtain the non-linear data required by the computations.
The chapter also addresses different homogenisation techniques
available in the literature in the linear and rigid-plastic case,
aiming at defining a catalogue and at discussing the advantages and
disadvantages of the different approaches. Special attention is given
to stress assumed models based either on a polynomial expansion
of the micro-stress field or in the discretization of the unit cell by
means of a few constant stress finite elements CST with joints reduced
to interfaces. Finally, the aspects of seismic assessment are
presented and case studies involving the use of macro-block analysis,
static (pushover) analysis and time integration analysis are
discussed.(undefined
Time-integrated luminosity recorded by the BABAR detector at the PEP-II e+e- collider
This article is the Preprint version of the final published artcile which can be accessed at the link below.We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the Ď(4S), Ď(3S), and Ď(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-âe+e- and (for the Ď(4S) only) e+e-âÎź+Îź- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e+e-âe+e- and e+e-âÎź+Îź-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the Ď(3S) and Ď(2S) resonances, an additional uncertainty arises due to Ďâe+e-X background. For data collected off the Ď resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the Ď(4S), 0.58% (0.72%) for the Ď(3S), and 0.68% (0.88%) for the Ď(2S).This work is supported by the US Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat Ă lâEnergie Atomique and Institut National de Physique NuclĂŠaire et de Physiquedes Particules (France), the Bundesministerium fĂźr Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Ciencia e InnovaciĂłn (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A.P. Sloan Foundation (USA)
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV
The Lambda(b) differential production cross section and the cross section
ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum
pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7
TeV using data collected by the CMS experiment at the LHC. The measurements are
based on Lambda(b) decays reconstructed in the exclusive final state J/Psi
Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and
Lambda to proton pion, using a data sample corresponding to an integrated
luminosity of 1.9 inverse femtobarns. The product of the cross section times
the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls
faster than that of b mesons. The measured value of the cross section times the
branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06
+/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for
anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are
statistical and systematic, respectively.Comment: Submitted to Physics Letters
Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV
A search is presented for physics beyond the standard model (BSM) in final
states with a pair of opposite-sign isolated leptons accompanied by jets and
missing transverse energy. The search uses LHC data recorded at a
center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to
an integrated luminosity of approximately 5 inverse femtobarns. Two
complementary search strategies are employed. The first probes models with a
specific dilepton production mechanism that leads to a characteristic kinematic
edge in the dilepton mass distribution. The second strategy probes models of
dilepton production with heavy, colored objects that decay to final states
including invisible particles, leading to very large hadronic activity and
missing transverse energy. No evidence for an event yield in excess of the
standard model expectations is found. Upper limits on the BSM contributions to
the signal regions are deduced from the results, which are used to exclude a
region of the parameter space of the constrained minimal supersymmetric
extension of the standard model. Additional information related to detector
efficiencies and response is provided to allow testing specific models of BSM
physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO
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