98 research outputs found
Predator-Induced Vertical Behavior of a Ctenophore
Although many studies have focused on Mnemiopsis leidyi predation, little is known about the role of this ctenophore as prey when abundant in native and invaded pelagic systems. We examined the response of the ctenophore M. leidyi to the predatory ctenophore Beroe ovata in an experiment in which the two species could potentially sense each other while being physically separated. On average, M. leidyi responded to the predatorâs presence by increasing variability in swimming speeds and by lowering their vertical distribution. Such behavior may help explain field records of vertical migration, as well as stratified and near-bottom distributions of M. leidyi
System size dependence of strange particle yields and spectra at sqrt(s)=17.3 GeV
Yields and spectra of strange hadrons (K+, K-, phi, Lambda and Antilambda) as
well as of charged pions were measured in near central C+C and Si+Si collisions
at 158 AGeV beam energy with the NA49 detector. Together with earlier data for
p+p, S+S and Pb+Pb reactions the system size dependence can be studied.
Relative strangeness production rises fast and saturates at about 60
participating nucleons; the net hyperon spectra show an increasing shift
towards midrapidity for larger colliding nuclei. An interpretation based on the
formation of coherent systems of increasing volume is proposed. The transverse
mass spectra can be described by a blast wave ansatz. Increasing flow velocity
is accompanied by decreasing temperatures for both kinetic and chemical freeze
out. The increasing gap between inelastic and elastic decoupling leaves space
for rescattering.Comment: 8 pages, 6 figures, Proceedings of the Hot Quarks 2004 worksho
Why Do Evaluations of eHealth Programs Fail? An Alternative Set of Guiding Principles
Trisha Greenhalgh and Jill Russell discuss the relative merits of âscientificâ and âsocial practiceâ approaches to evaluation and argue that eHealth evaluation is in need of a paradigm shift
ESKIMO1 Disruption in Arabidopsis Alters Vascular Tissue and Impairs Water Transport
Water economy in agricultural practices is an issue that is being addressed through studies aimed at understanding both plant water-use efficiency (WUE), i.e. biomass produced per water consumed, and responses to water shortage. In the model species Arabidopsis thaliana, the ESKIMO1 (ESK1) gene has been described as involved in freezing, cold and salt tolerance as well as in water economy: esk1 mutants have very low evapo-transpiration rates and high water-use efficiency. In order to establish ESK1 function, detailed characterization of esk1 mutants has been carried out. The stress hormone ABA (abscisic acid) was present at high levels in esk1 compared to wild type, nevertheless, the weak water loss of esk1 was independent of stomata closure through ABA biosynthesis, as combining mutant in this pathway with esk1 led to additive phenotypes. Measurement of root hydraulic conductivity suggests that the esk1 vegetative apparatus suffers water deficit due to a defect in water transport. ESK1 promoter-driven reporter gene expression was observed in xylem and fibers, the vascular tissue responsible for the transport of water and mineral nutrients from the soil to the shoots, via the roots. Moreover, in cross sections of hypocotyls, roots and stems, esk1 xylem vessels were collapsed. Finally, using Fourier-Transform Infrared (FTIR) spectroscopy, severe chemical modifications of xylem cell wall composition were highlighted in the esk1 mutants. Taken together our findings show that ESK1 is necessary for the production of functional xylem vessels, through its implication in the laying down of secondary cell wall components
Stress-Induced Activation of Heterochromatic Transcription
Constitutive heterochromatin comprising the centromeric and telomeric parts of chromosomes includes DNA marked by high levels of methylation associated with histones modified by repressive marks. These epigenetic modifications silence transcription and ensure stable inheritance of this inert state. Although environmental cues can alter epigenetic marks and lead to modulation of the transcription of genes located in euchromatic parts of the chromosomes, there is no evidence that external stimuli can globally destabilize silencing of constitutive heterochromatin. We have found that heterochromatin-associated silencing in Arabidopsis plants subjected to a particular temperature regime is released in a genome-wide manner. This occurs without alteration of repressive epigenetic modifications and does not involve common epigenetic mechanisms. Such induced release of silencing is mostly transient, and rapid restoration of the silent state occurs without the involvement of factors known to be required for silencing initiation. Thus, our results reveal new regulatory aspects of transcriptional repression in constitutive heterochromatin and open up possibilities to identify the molecular mechanisms involved
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Corporate reputation past and future: a review and integration of existing literature and a framework for future research
The concept of corporate reputation is steadily growing in interest among management researchers and practitioners. In this article, we trace key milestones in the development of reputation literature over the past six decades to suggest important research gaps as well as to provide contextual background for a subsequent integration of approaches and future outlook. In particular we explore the need for better categorised outcomes; a wider range of causes; and a deeper understanding of contingencies and moderators to advance the field beyond its current state while also taking account of developments in the macro business environment. The article concludes by presenting a novel reputation framework that integrates insights from reputation theory and studies, outlines gaps in knowledge and offers directions for future research
Combined Tevatron upper limit on gg->H->W+W- and constraints on the Higgs boson mass in fourth-generation fermion models
Report number: FERMILAB-PUB-10-125-EWe combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg->H->W+W- in p=pbar collisions at the Fermilab Tevatron Collider at sqrt{s}=1.96 TeV. With 4.8 fb-1 of integrated luminosity analyzed at CDF and 5.4 fb-1 at D0, the 95% Confidence Level upper limit on \sigma(gg->H) x B(H->W+W-) is 1.75 pb at m_H=120 GeV, 0.38 pb at m_H=165 GeV, and 0.83 pb at m_H=200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% Confidence Level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process ggâHâW+W- in ppÌ
collisions at the Fermilab Tevatron Collider at âs=1.96ââTeV. With 4.8ââfb-1 of integrated luminosity analyzed at CDF and 5.4ââfb-1 at D0, the 95% confidence level upper limit on Ï(ggâH)ĂB(HâW+W-) is 1.75 pb at mH=120ââGeV, 0.38 pb at mH=165ââGeV, and 0.83 pb at mH=200ââGeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.Peer reviewe
Search for narrow resonances lighter than mesons
9 pages, 3 figuresWe report a search for narrow resonances, produced in collisions at TeV, that decay into muon pairs with invariant mass between 6.3 and 9.0 GeV/c^2. The data, collected with the CDF~II detector at the Fermilab Tevatron collider, correspond to an integrated luminosity of 630 pb. We use the dimuon invariant mass distribution to set 90% upper credible limits of about 1% to the ratio of the production cross section times muonic branching fraction of possible narrow resonances to that of the meson.We report a search for narrow resonances, produced in collisions at TeV, that decay into muon pairs with invariant mass between 6.3 and 9.0 GeV/c 2. The data, collected with the CDF II detector at the Fermilab Tevatron collider, correspond to an integrated luminosity of 630 pbâ1. We use the dimuon invariant mass distribution to set 90% upper credible limits of about 1% to the ratio of the production cross section times muonic branching fraction of possible narrow resonances to that of the Ï(1S) meson.Peer reviewe
Measurement of D s <sup>±</sup> production asymmetry in pp collisions at âs=7 and 8 TeV
The inclusive production asymmetry is measured in collisions
collected by the LHCb experiment at centre-of-mass energies of
and 8 TeV. Promptly produced mesons are used, which decay as
, with . The measurement is
performed in bins of transverse momentum, , and rapidity, ,
covering the range GeV and . No kinematic
dependence is observed. Evidence of nonzero production asymmetry is
found with a significance of 3.3 standard deviations.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2018-010.htm
Observation of the decay Î <sub>b</sub> <sup>0</sup> âââÏ(2S)pÏ<sup>â</sup>
International audienceThe Cabibbo-suppressed decay Î âââÏ(2S)pÏ is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb of integrated luminosity at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The Ï(2S) mesons are reconstructed in the ΌΌ final state. The branching fraction with respect to that of the Î âââÏ(2S)pK decay mode is measured to b
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