287 research outputs found

    Optimal data partitioning, multispecies coalescent and Bayesian concordance analyses resolve early divergences of the grape family (Vitaceae)

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    Evolutionary rate heterogeneity and rapid radiations are common phenomena in organismal evolution and represent major challenges for reconstructing deep-level phylogenies. Here we detected substantial conflicts in and among data sets as well as uncertainty concerning relationships among lineages of Vitaceae from individual gene trees, supernetworks and tree certainty values. Congruent deep-level relationships of Vitaceae were retrieved by comprehensive comparisons of results from optimal partitioning analyses, multispecies coalescent approaches and the Bayesian concordance method. We found that partitioning schemes selected by PartitionFinder were preferred over those by gene or by codon position, and the unpartitioned model usually performed the worst. For a data set with conflicting signals, however, the unpartitioned model outperformed models that included more partitions, demonstrating some limitations to the effectiveness of concatenation for these data. For a transcriptome data set, fast coalescent methods (STAR and MP-EST) and a Bayesian concordance approach yielded congruent topologies with trees from the concatenated analyses and previous studies. Our results highlight that well-resolved gene trees are critical for the effectiveness of coalescent-based methods. Future efforts to improve the accuracy of phylogenomic analyses should emphasize the development of newmethods that can accommodate multiple biological processes and tolerate missing data while remaining computationally tractable. (C) The Willi Hennig Society 2017.National Natural Science Foundation of China [NNSF 31500179, 31590822, 31270268]; National Basic Research Program of China [2014CB954101]; National Science Foundation [DEB0743474]; Smithsonian Scholarly Studies Grant Program and the Endowment Grant Program; CAS/SAFEA International Partnership Program for Creative Research Teams; Laboratory of Analytical Biology of the National Museum of Natural History, Smithsonian Institution; Science and Technology Basic Work [2013FY112100]info:eu-repo/semantics/publishedVersio

    Northern European trees show a progressively diminishing response to increasing atmospheric carbon dioxide concentrations

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    In order to predict accurately how elevated atmospheric CO2 concentrations will affect the global carbon cycle, it is necessary to know how trees respond to increasing CO2 concentrations. In this paper we examine the response over the period AD 1895 – 1994 of three tree species growing across northern Europe to increases in atmospheric CO2 concentrations using parameters derived from stable carbon isotope ratios of trunk cellulose. Using the isotope data we calculate values of intrinsic water-use efficiency (IWUE) and intercellular CO2 concentrations in the leaf (ci). Our results show that trees have responded to higher levels of atmospheric CO2 by increasing IWUE whilst generally maintaining constant ci values. However, the IWUE of most of the trees in this study has not continued to rise in line with increasing atmospheric CO2. This behaviour has implications for estimations of future terrestrial carbon storage

    Intercalibration of the barrel electromagnetic calorimeter of the CMS experiment at start-up

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    Calibration of the relative response of the individual channels of the barrel electromagnetic calorimeter of the CMS detector was accomplished, before installation, with cosmic ray muons and test beams. One fourth of the calorimeter was exposed to a beam of high energy electrons and the relative calibration of the channels, the intercalibration, was found to be reproducible to a precision of about 0.3%. Additionally, data were collected with cosmic rays for the entire ECAL barrel during the commissioning phase. By comparing the intercalibration constants obtained with the electron beam data with those from the cosmic ray data, it is demonstrated that the latter provide an intercalibration precision of 1.5% over most of the barrel ECAL. The best intercalibration precision is expected to come from the analysis of events collected in situ during the LHC operation. Using data collected with both electrons and pion beams, several aspects of the intercalibration procedures based on electrons or neutral pions were investigated

    Solar parameters for modeling interplanetary background

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    The goal of the Fully Online Datacenter of Ultraviolet Emissions (FONDUE) Working Team of the International Space Science Institute in Bern, Switzerland, was to establish a common calibration of various UV and EUV heliospheric observations, both spectroscopic and photometric. Realization of this goal required an up-to-date model of spatial distribution of neutral interstellar hydrogen in the heliosphere, and to that end, a credible model of the radiation pressure and ionization processes was needed. This chapter describes the solar factors shaping the distribution of neutral interstellar H in the heliosphere. Presented are the solar Lyman-alpha flux and the solar Lyman-alpha resonant radiation pressure force acting on neutral H atoms in the heliosphere, solar EUV radiation and the photoionization of heliospheric hydrogen, and their evolution in time and the still hypothetical variation with heliolatitude. Further, solar wind and its evolution with solar activity is presented in the context of the charge exchange ionization of heliospheric hydrogen, and in the context of dynamic pressure variations. Also the electron ionization and its variation with time, heliolatitude, and solar distance is presented. After a review of all of those topics, we present an interim model of solar wind and the other solar factors based on up-to-date in situ and remote sensing observations of solar wind. Results of this effort will further be utilised to improve on the model of solar wind evolution, which will be an invaluable asset in all heliospheric measurements, including, among others, the observations of Energetic Neutral Atoms by the Interstellar Boundary Explorer (IBEX).Comment: Chapter 2 in the planned "Cross-Calibration of Past and Present Far UV Spectra of Solar System Objects and the Heliosphere", ISSI Scientific Report No 12, ed. R.M. Bonnet, E. Quemerais, M. Snow, Springe

    Search for the associated production of the Higgs boson with a top-quark pair

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    A search for the standard model Higgs boson produced in association with a top-quark pair t t ¯ H (tt¯H) is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb −1 and 19.7 fb −1 collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H → hadrons, H → photons, and H → leptons. The results are characterized by an observed t t ¯ H tt¯H signal strength relative to the standard model cross section, μ = σ/σ SM ,under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is μ = 2.8 ± 1.0 for a Higgs boson mass of 125.6 GeV

    Measurement of prompt Jψ\psi pair production in pp collisions at \sqrt s = 7 Tev

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    Production of prompt J/ ψ meson pairs in proton-proton collisions at s s√ = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 fb −1 . The two J/ ψ mesons are fully reconstructed via their decays into μ + μ − pairs. This observation provides for the first time access to the high-transverse-momentum region of J/ ψ pair production where model predictions are not yet established. The total and differential cross sections are measured in a phase space defined by the individual J/ ψ transverse momentum ( p T J/ ψ ) and rapidity (| y J/ ψ |): | y J/ ψ | 6.5 GeV/ c ; 1.2 4.5 GeV/ c . The total cross section, assuming unpolarized prompt J/ ψ pair production is 1.49 ± 0.07 (stat) ±0.13 (syst) nb. Different assumptions about the J/ ψ polarization imply modifications to the cross section ranging from −31% to +27%

    Measurements of the t(t)Overbar charge asymmetry using the dilepton decay channel in pp collisions at root s=7 TeV

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    The tt¯ charge asymmetry in proton-proton collisions at s√ = 7 TeV is measured using the dilepton decay channel (ee, e μ , or μμ ). The data correspond to a total integrated luminosity of 5.0 fb −1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = −0 . 010 ± 0 . 017 (stat . ) ± 0 . 008 (syst . ) and AlepC = 0 . 009 ± 0 . 010 (stat . ) ± 0 . 006 (syst . ). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the tt¯ system. All measurements are consistent with the expectations of the standard model

    Combination of searches for Higgs boson pairs in pp collisions at \sqrts = 13 TeV with the ATLAS detector

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    This letter presents a combination of searches for Higgs boson pair production using up to 36.1 fb(-1) of proton-proton collision data at a centre-of-mass energy root s = 13 TeV recorded with the ATLAS detector at the LHC. The combination is performed using six analyses searching for Higgs boson pairs decaying into the b (b) over barb (b) over bar, b (b) over barW(+)W(-), b (b) over bar tau(+)tau(-), W+W-W+W-, b (b) over bar gamma gamma and W+W-gamma gamma final states. Results are presented for non-resonant and resonant Higgs boson pair production modes. No statistically significant excess in data above the Standard Model predictions is found. The combined observed (expected) limit at 95% confidence level on the non-resonant Higgs boson pair production cross-section is 6.9 (10) times the predicted Standard Model cross-section. Limits are also set on the ratio (kappa(lambda)) of the Higgs boson self-coupling to its Standard Model value. This ratio is constrained at 95% confidence level in observation (expectation) to -5.0 &lt; kappa(lambda) &lt; 12.0 (-5.8 &lt; kappa(lambda) &lt; 12.0). In addition, limits are set on the production of narrow scalar resonances and spin-2 Kaluza-Klein Randall-Sundrum gravitons. Exclusion regions are also provided in the parameter space of the habemus Minimal Supersymmetric Standard Model and the Electroweak Singlet Model. For complete list of authors see http://dx.doi.org/10.1016/j.physletb.2019.135103</p
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