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19,501 result(s) for "Dennis, S. R."
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Phenotypic convergence along a gradient of predation risk
A long-standing question in ecology is whether phenotypic plasticity, rather than selection per se, is responsible for phenotypic variation among populations. Plasticity can increase or decrease variation, but most previous studies have been limited to single populations, single traits and a small number of environments assessed using univariate reaction norms. Here, examining two genetically distinct populations of Daphnia pulex with different predation histories, we quantified predator-induced plasticity among 11 traits along a fine-scale gradient of predation risk by a predator (Chaoborus) common to both populations. We test the hypothesis that plasticity can be responsible for convergence in phenotypes among different populations by experimentally characterizing multivariate reaction norms with phenotypic trajectory analysis (PTA). Univariate analyses showed that all genotypes increased age and size at maturity, and invested in defensive spikes (neckteeth), but failed to quantitatively describe whole-organism response. In contrast, PTA quantified and qualified the phenotypic strategy the organism mobilized against the selection pressure. We demonstrate, at the whole-organism level, that the two populations occupy different areas of phenotypic space in the absence of predation but converge in phenotypic space as predation threat increases.
Cat-Scratch Disease with Paravertebral Mass and Osteomyelitis
The case of a 9-year-old girl with cat-scratch disease (CSD) complicated by development of a paravertebral mass and osteomyelitis is presented. Following multiple scratches and inguinal lymphadenopathy, she developed back pain, and imaging demonstrated a paravertebral mass with evidence of osteomyelitis involving vertebra T9. The diagnosis was made on the basis of detection of Bartonella henselae by use of molecular techniques on an aspirate from the vertebral column and supportive serology for infection with B. henselae. Eleven other cases of this unusual manifestation associated with CSD have been reported in the literature and are reviewed. The patient was treated with gentamicin, followed by rifampicin and trimethoprim-sulfamethoxazole, orally and made a favorable recovery over 7 months. This is comparable with other case reports, regardless of the choice of antibiotic therapy. CSD in immunocompetent hosts is not always self-limiting, and tissues beyond the lymph nodes can be involved.
Phase I Evaluation of Zalcitabine Administered to Human Immunodeficiency Virus-Infected Children
The safety, tolerability, and pharmacokinetics of zalcitabine (ddC) in a single oral dose (0.02 mg! kg) was evaluated in 23 mildly symptomatic human immunodeficiency virus-infected children (mean age, 4.2 years). After administration of ddC, blood samples were obtained at 0.5, 1, 1.5, 2, 4, 6, and 8 h for analysis. The drug was well tolerated and no side effects were noted. Plasma ddC levels were determined by ion spray liquid chromatography/tandem mass spectrometry. ddC was rapidly absorbed, with a mean maximum plasma concentration of 9.3 ng/mL (range, 3.2–14.1) attained within a mean of 1 h (range, 0.5–2.0). Mean elimination half-life was 1.4 h (range, 1.03.5), mean area under the plasma concentration-time curve was 25 ng ·h/mL (range, 11–37), and mean total body clearance was 14.6 mL/min/kg (range, 8.9–30.6). Plasma concentrations were lower and the half-life shorter in these children than in adults given comparable doses, suggesting that ddC may be cleared more rapidly in children than adults.
Multi-branching flows from one mother tube to many daughters or to a network
Multiply branching fluid flows are modelled in two contexts. The first (type I) is for one-to-many branching. Computations are described for flow through a channel, with fully developed motion upstream, which branches abruptly into a number of subchannels downstream. The differences in pressure between the upstream end of the channel and the downstream ends of the subchannels are substantial. Comparisons with recent analytical predictions show fair agreement for Reynolds numbers in the low tens and above. The second context (type II) has successive generations of bifurcation in a network. Modelling, computations and analysis include the effects of many bifurcations.
Measurements of ν̅ μ and ν̅ μ + ν μ charged-current cross-sections without detected pions or protons on water and hydrocarbon at a mean anti-neutrino energy of 0.86 GeV
We report measurements of the flux-integrated ν̅μ and ν̅μ + νμ charged-current cross-sections on water and hydrocarbon targets using the T2K anti-neutrino beam with a mean beam energy of 0.86 GeV. The signal is defined as the (anti-)neutrino charged-current interaction with one induced$\\mu^\\pm$and no detected charged pion or proton. These measurements are performed using a new WAGASCI module recently added to the T2K setup in combination with the INGRID Proton Module. The phase space of muons is restricted to the high-detection efficiency region,$p_{\\mu}>400~{\\rm MeV}/c$and$\\theta_{\\mu}<30^{\\circ}$ , in the laboratory frame. An absence of pions and protons in the detectable phase spaces of$p_{\\pi}>200~{\\rm MeV}/c$ ,$\\theta_{\\pi}<70^{\\circ}$and$p_{\\rm p}>600~{\\rm MeV}/c$ ,$\\theta_{\\rm p}<70^{\\circ}$is required. In this paper, both the$\\overline{\\nu}_\\mu$cross-sections and$\\overline{\\nu}_\\mu+\\nu_\\mu$cross-sections on water and hydrocarbon targets and their ratios are provided by using the D’Agostini unfolding method. The results of the integrated$\\overline{\\nu}_\\mu$cross-section measurements over this phase space are$\\sigma_{\\rm H_{2}O}=(1.082\\pm0.068(\\rm stat.)^{+0.145}_{-0.128}(\\rm syst.)) \\times 10^{-39}\\,{\\rm cm^{2} / nucleon}$ ,$\\sigma_{\\rm CH}=(1.096\\pm0.054(\\rm stat.)^{+0.132}_{-0.117}(\\rm syst.)) \\times 10^{-39}\\,{\\rm cm^{2} / nucleon}$ , and$\\sigma_{\\rm H_{2}O}/\\sigma_{\\rm CH} = 0.987\\pm0.078(\\rm stat.)^{+0.093}_{-0.090}(\\rm syst.)$ . The$\\overline{\\nu}_\\mu+\\nu_\\mu$cross-section is$\\sigma_{\\rm H_{2}O} = (1.155\\pm0.064(\\rm stat.)^{+0.148}_{-0.129}(\\rm syst.)) \\times 10^{-39}\\,{\\rm cm^{2} / nucleon}$ ,$\\sigma_{\\rm CH}=(1.159\\pm0.049(\\rm stat.)^{+0.129}_{-0.115}(\\rm syst.)) \\times 10^{-39}\\,{\\rm cm^{2} / nucleon}$ , and$\\sigma_{\\rm H_{2}O}/\\sigma_{\\rm CH}=0.996\\pm0.069(\\rm stat.)^{+0.083}_{-0.078}(\\rm syst.)$ .
White Paper on Light Sterile Neutrino Searches and Related Phenomenology
This white paper provides a comprehensive review of our present understanding of experimental neutrino anomalies that remain unresolved, charting the progress achieved over the last decade at the experimental and phenomenological level, and sets the stage for future programmatic prospects in addressing those anomalies. It is purposed to serve as a guiding and motivational \"encyclopedic\" reference, with emphasis on needs and options for future exploration that may lead to the ultimate resolution of the anomalies. We see the main experimental, analysis, and theory-driven thrusts that will be essential to achieving this goal being: 1) Cover all anomaly sectors -- given the unresolved nature of all four canonical anomalies, it is imperative to support all pillars of a diverse experimental portfolio, source, reactor, decay-at-rest, decay-in-flight, and other methods/sources, to provide complementary probes of and increased precision for new physics explanations; 2) Pursue diverse signatures -- it is imperative that experiments make design and analysis choices that maximize sensitivity to as broad an array of these potential new physics signatures as possible; 3) Deepen theoretical engagement -- priority in the theory community should be placed on development of standard and beyond standard models relevant to all four short-baseline anomalies and the development of tools for efficient tests of these models with existing and future experimental datasets; 4) Openly share data -- Fluid communication between the experimental and theory communities will be required, which implies that both experimental data releases and theoretical calculations should be publicly available; and 5) Apply robust analysis techniques -- Appropriate statistical treatment is crucial to assess the compatibility of data sets within the context of any given model.
First simultaneous measurement of differential muon-neutrino charged-current cross sections on argon for final states with and without protons using MicroBooNE data
We report the first double-differential neutrino-argon cross section measurement made simultaneously for final states with and without protons for the inclusive muon neutrino charged-current interaction channel. The proton kinematics of this channel are further explored with a differential cross section measurement as a function of the leading proton's kinetic energy that extends across the detection threshold. These measurements utilize data collected using the MicroBooNE detector from 6.4\\(\\times10^{20}\\) protons on target from the Fermilab Booster Neutrino Beam with a mean neutrino energy of \\(\\sim\\)0.8 GeV. Extensive data-driven model validation utilizing the conditional constraint formalism is employed. This motivates enlarging the uncertainties with an empirical reweighting approach to minimize the possibility of extracting biased cross section results. The extracted nominal flux-averaged cross sections are compared to widely used event generator predictions revealing severe mismodeling of final states without protons for muon neutrino charged-current interactions, possibly from insufficient treatment of final state interactions. These measurements provide a wealth of new information useful for improving event generators which will enhance the sensitivity of precision measurements in neutrino experiments.
Measurement of ambient radon progeny decay rates and energy spectra in liquid argon using the MicroBooNE detector
We report measurements of radon progeny in liquid argon within the MicroBooNE time projection chamber (LArTPC). The presence of specific radon daughters in MicroBooNE's 85 metric tons of active liquid argon bulk is probed with newly developed charge-based low-energy reconstruction tools and analysis techniques to detect correlated \\(^{214}\\)Bi-\\(^{214}\\)Po radioactive decays. Special datasets taken during periods of active radon doping enable new demonstrations of the calorimetric capabilities of single-phase neutrino LArTPCs for \\(\\beta\\) and \\(\\alpha\\) particles with electron-equivalent energies ranging from 0.1 to 3.0 MeV. By applying \\(^{214}\\)Bi-\\(^{214}\\)Po detection algorithms to data recorded over a 46-day period, no statistically significant presence of radioactive \\(^{214}\\)Bi is detected, and a limit on the activity is placed at \\(<0.35\\) mBq/kg at the 95% confidence level. This bulk \\(^{214}\\)Bi radiopurity limit -- the first ever reported for a liquid argon detector incorporating liquid-phase purification -- is then further discussed in relation to the targeted upper limit of 1 mBq/kg on bulk \\(^{222}\\)Rn activity for the DUNE neutrino detector.
Observation of Radon Mitigation in MicroBooNE by a Liquid Argon Filtration System
The MicroBooNE liquid argon time projection chamber (LArTPC) maintains a high level of liquid argon purity through the use of a filtration system that removes electronegative contaminants in continuously-circulated liquid, recondensed boil off, and externally supplied argon gas. We use the MicroBooNE LArTPC to reconstruct MeV-scale radiological decays. Using this technique we measure the liquid argon filtration system's efficacy at removing radon. This is studied by placing a 500 kBq \\(^{222}\\)Rn source upstream of the filters and searching for a time-dependent increase in the number of radiological decays in the LArTPC. In the context of two models for radon mitigation via a liquid argon filtration system, a slowing mechanism and a trapping mechanism, MicroBooNE data supports a radon reduction factor of greater than 99.999% or 97%, respectively. Furthermore, a radiological survey of the filters found that the copper-based filter material was the primary medium that removed the \\(^{222}\\)Rn. This is the first observation of radon mitigation in liquid argon with a large-scale copper-based filter and could offer a radon mitigation solution for future large LArTPCs.
On the fully developed flow in a curved pipe at large Dean number
In this paper we consider the asymptotic form, for large Dean number, of the solution which describes the fully developed laminar flow in a curved pipe of circular cross section. Although we have not been able to provide a complete solution we present strong evidence in favour of an asymptotic structure which is based upon an in viscid core flow enclosed by viscous boundary layers at the pipe wall.