13,886 research outputs found

    Natural Infection of Southern Highbush Blueberry ( Vaccinium corymbosum Interspecific Hybrids) by Xylella fastidiosa subsp. fastidiosa .

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    Xylella fastidiosa (Xf) is an emerging insect-vectored, xylem-limited bacterium that can cause disease on several economically important fruit and tree crops including almond, blueberry, citrus, grapevine, peach, and pecan. On blueberry, Xf causes bacterial leaf scorch (BLS), which is prevalent in the southeastern United States. This disease, previously reported to be caused by Xf subsp. multiplex (Xfm), can result in rapid plant decline and death of southern highbush (SHB) blueberry cultivars. In 2017, a survey of blueberry plantings in southern Georgia (U.S.A.) confirmed the presence of Xf-infected plants in eight of nine sites examined, and seven isolates were cultured from infected plants. Genetic characterization of these isolates through single-locus and multilocus sequence analysis revealed that three isolates from two sites belonged to Xf subsp. fastidiosa (Xff), with significant similarity to isolates from grapevine. After these three isolates were artificially inoculated onto greenhouse-grown SHB blueberries (cv. 'Rebel'), symptoms typical of BLS developed, and Xff infection was confirmed through genetic characterization and reisolation of the bacterium to fulfill Koch's postulates. Because all previously reported Xf isolates from blueberry have been characterized as Xfm, this is the first time that isolation of Xff has been reported from naturally infected blueberry plantings. The potential impact of Xff isolates on disease management in blueberry requires further exploration. Furthermore, given that isolates from both Xfm and Xff were obtained within a single naturally infected blueberry planting, blueberry in southern Georgia may provide opportunities for intersubspecific recombination between Xff and Xfm isolates

    Animal experimentation: implementation and application of the 3Rs

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    Despite the development of powerful molecular biological techniques and technologies, studies involving research animals remain a key component of discovery biology, and in the discovery and development of new medicines. In 1959, The Principles of Humane Experimental Technique, the 3Rs (Replacement, Reduction and Refinement) were developed to provide a framework to ensure animal research was undertaken as humanely as possible. Sixty years since their inception, the extent to which the 3Rs have been adopted and implemented by the global scientific and medical research communities has unfortunately been slow and patchy. However, this situation is changing rapidly as awareness increases, not only of the 3Rs themselves, but of the impact of animal welfare on the reproducibility, reliability and translatability of data from animal studies

    Logarithmic Operators and Dynamical Extention of The Symmetry Group in the Bosonic SU(2)_0 and SUSY SU(2)_2 WZNW Models

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    We study the operator product expansion in the bosonic SU(2)0SU(2)_0 and SUSY SU(2)2SU(2)_2 WZNW models. We find that these OPEs contain both logarithmic operators and new conserved currents, leading to an extension of the symmetry group.Comment: 16 pages, Late

    A Configurable Matchmaking Framework for Electronic Marketplaces

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    E-marketplaces constitute a major enabler of B2B and B2C e-commerce activities. This paper proposes a framework for one of the central activities of e-marketplaces: matchmaking of trading intentions lodged by market participants. The framework identifies a core set of concepts and functions that are common to all types of marketplaces and can serve as the basis for describing the distinct styles of matchmaking employed within various market mechanisms. A prototype implementation of the framework based on Web services technology is presented, illustrating its ability to be dynamically configured to meet specific market needs and its potential to serve as a foundation for more fully fledged e-marketplace frameworks

    Testing the Nature of the D_{sJ}^*(2317)^+ and D_{sJ}(2463)^+ States Using Radiative Transitions

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    The Babar and CLEO collaborations have recently observed states decaying to D_s^+\pi^0 and D_s^{*+}\pi^0 respectively and suggest the possible explanation that they are the missing P-wave c\bar{s} states with J^P=0^+ and 1^+. In this note we compare the properties of the D_{sJ}^*(2317)^+ and D_{sJ}(2463)^+ states to those expected of the c\bar{s} D_{s0}^* and D_{s1} states. We expect the D_{s0}^* and D_{s1} with the reported masses to be extremely narrow, \Gamma \sim {\cal O}(10\hbox{keV}), with large branching ratios to D^*_s\gamma for the D_{s0}^* and to D^*_s\gamma and D_s\gamma for the D_{s1}. Crucial to this interpretation of the Babar and CLEO observations is the measurement of the radiative transitions. We note that it may be possible to observe the Ds1(2536)D_{s1}(2536) in radiative transitions to the Ds∗D_s^*.Comment: Major revisions to include recent observation by CLEO of D_{sJ}(2463)^+ including change of title and additional radiative transitions included in results. Conclusions are not change

    Vacuum Instability in Topologically Massive Gauge Theory

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    We find the critical charge for a topologically massive gauge theory for any gauge group, generalising our earlier result for SU(2). The relation between critical charges in TMGT, singular vectors in the WZNW model and logarithmic CFT is investigated.Comment: 14 pages, Late

    Analytical Approximations of Critical Clearing Time for Parametric Analysis of Power System Transient Stability

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    An analytic approximation for the critical clearing time (CCT) metric is derived from direct methods for power system stability. The formula has been designed to incorporate as many features of transient stability analysis as possible such as different fault locations and different post-fault network states. The purpose of this metric is to analyse trends in stability (in terms of CCT) of power systems under the variation of a system parameter. The performance of this metric to measure stability trends is demonstrated on an aggregated power network, the so-called two machine infinite bus network, by varying load parameters in the full bus admittance matrix using numerical continuation. The metric is compared to two other expressions for the CCT which incorporate additional non-linearities present in the model

    Test-Retest Reliability and Minimum Detectable Change for Various Frontal Plane Projection Angles during Dynamic Tasks

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    Objective: Establish between-day test-retest reliability metrics for 2-dimensional frontal plane projection angles (FPPAs) during the lateral step-down (LSD), single-limb squat (SLS), single-limb landing (SLL), and drop vertical jump (DVJ). Design: Test-retest reliability study Setting: University laboratory Participants: 20 healthy adults (12 female, age = 23.60±1.93 years old, body mass index = 24.26±2.54 kg/m2) were tested on 2 separate occasions 7-14 days apart. Main Outcome Measures: Intraclass correlation coefficients (ICC), standard errors of the measurement (SEM), and minimal detectable change (MDC) values across the LSD, SLS, SLL, and DVJ for the following body region variables: trunk, trunk on pelvis, pelvis, hip, thigh to vertical, knee, and shank to vertical. Results: There was moderate-to-substantial between-day test-retest reliability for nearly all body regions across all tasks (ICC = 0.65-0.96). SEM values varied across body regions and tasks (0.9-3.5 degrees). MDCs were variable (2.3-9.8 degrees). Of the body regions, MDCs were largest for the knee and hip. By task, MDCs were lowest for the LSD. Conclusions: This study identified between-day test-retest reliability metrics for 2-dimensional FPPAs across a variety of body regions during commonly assessed clinical tasks. These data allow clinicians and researchers to more confidently assess true change between assessments or over time

    Reimagining laboratory‐based immunology education in the time of COVID‐19

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    The pandemic has brought challenges to teaching lab and research skills. Here Nigel Francis and colleagues explore the diverse approaches taken to replace lab-based immunology teaching, explain how networks of educators have driven this innovation and discuss the importance of retaining best practice into the future
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