1,718 research outputs found

    Population dynamics of grape phylloxera in California vineyards

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    Field monitoring was conducted to investigate population growth of grape phylloxera, Daktulosphaira vitifoliae (Fitch), in commercial grapevines in California. Phylloxera populations started from very low densities each spring, they increased exponentially and peaked during mid-summer, and then declined from mid-to late-summer. A second population peak was observed in the fall. Populations increased and declined simultaneously across all age classes. Egg populations were highest, followed by 1st and 2nd and then 3rd and 4th instars; adult populations were the lowest. The distribution of age classes as a proportion of the total population indicated a higher intrinsic rate of increase in field vines in spring and early summer than was observed in the laboratory. Densities of phylloxera on tuberosities were highest during the summer and coincided with the population maximum. Densities of phylloxera on nodosities were highest in early spring and in the fall and coincided with periods of root flush. Evaluation of the relationship of soil temperatures to developing phylloxera suggested that decline of phylloxera populations in mid-and late-summer cannot be attributed to temperatures below a developmental threshold. Decreased root quality or quantity and mortality factors may explain this decline. Phylloxera overwintered as 1st or 2nd instars. Analysis of spatial distribution of phylloxera using Taylor's power law and Iwao's patchiness regression indicated that phylloxera populations are aggregated. The significance of this research with respect to phylloxera management is discussed

    MRI-based Surgical Planning for Lumbar Spinal Stenosis

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    The most common reason for spinal surgery in elderly patients is lumbar spinal stenosis(LSS). For LSS, treatment decisions based on clinical and radiological information as well as personal experience of the surgeon shows large variance. Thus a standardized support system is of high value for a more objective and reproducible decision. In this work, we develop an automated algorithm to localize the stenosis causing the symptoms of the patient in magnetic resonance imaging (MRI). With 22 MRI features of each of five spinal levels of 321 patients, we show it is possible to predict the location of lesion triggering the symptoms. To support this hypothesis, we conduct an automated analysis of labeled and unlabeled MRI scans extracted from 788 patients. We confirm quantitatively the importance of radiological information and provide an algorithmic pipeline for working with raw MRI scans

    Structural, magnetic and electrical properties of the hexagonal ferrites MFeO3 (M=Y, Yb, In)

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    We thank EPSRC for funding, STFC for providing neutron facilities and Diamond Light Source for provision of synchrotron facilities. We thank Dr Chiu Tang for assistance at Diamond and Dr A. Kusmartseva (University of Edinburgh) for assistance with the SQUID measurements. FDM thanks the Royal Society for a Research Fellowship.The hexagonal ferrites MFeO3 (M=Y, Yb, In) have been studied using a combination of neutron and X-ray powder diffraction, magnetic susceptibility, dielectric measurements and 57Fe Mössbauer spectroscopy. This study confirms the previously reported crystal structure of InFeO3 (YAlO3 structure type, space group P63/mmc), but YFeO3 and YbFeO3 both show a lowering of symmetry to at most P63cm (ferrielectric YMnO3 structure type). However, Mössbauer spectroscopy shows at least two distinct Fe sites for both YFeO3 and YbFeO3 and we suggest that the best model to rationalise this involves phase separation into more than one similar hexagonal YMnO3-like phase. Rietveld analysis of the neutron diffraction data was carried out using two hexagonal phases as a simplest case scenario. In both YFeO3 and YbFeO3, distinct dielectric anomalies are observed near 130 K and 150 K, respectively. These are tentatively correlated with weak anomalies in magnetic susceptibility and lattice parameters, for YFeO3 and YbFeO3, respectively, which may suggest a weak magnetoelectric effect. Comparison of neutron and X-ray powder diffraction shows evidence of long-range magnetic order in both YFeO3 and YbFeO3 at low temperatures. Due to poor sample crystallinity, the compositional and structural effects underlying the phase separation and possible magnetoelectric phenomena cannot be ascertained.PostprintPeer reviewe

    Technical Design Report for PANDA Electromagnetic Calorimeter (EMC)

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    This document presents the technical layout and the envisaged performance of the Electromagnetic Calorimeter (EMC) for the PANDA target spectrometer. The EMC has been designed to meet the physics goals of the PANDA experiment. The performance figures are based on extensive prototype tests and radiation hardness studies. The document shows that the EMC is ready for construction up to the front-end electronics interface

    Sepsis carries a high mortality among hospitalised adults in Malawi in the era of antiretroviral therapy scale-up: A longitudinal cohort study

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    Objective: To assess mortality risk among adults presenting to an African teaching hospital with sepsis and severe sepsis in a setting of high HIV prevalence and widespread ART uptake. Methods: Prospective cohort study of adults (age ≥16 years) admitted with clinical suspicion of severe infection between November 2008 and January 2009 to Queen Elizabeth Central Hospital, a 1250-bed government-funded hospital in Blantyre, Malawi. Demographic, clinical and laboratory information, including blood and cerebrospinal fluid cultures were obtained on admission. Results: Data from 213 patients (181 with sepsis and 32 with severe sepsis; M:F = 2:3) were analysed. 161 (75.6%) patients were HIV-positive. Overall mortality was 22%, rising to 50% amongst patients with severe sepsis. The mortality of all sepsis patients commenced on antiretroviral therapy (ART) within 90 days was 11/28 (39.3%) compared with 7/42 (16.7%) among all sepsis patients on ART for greater than 90 days (p = 0.050). Independent associations with death were hypoxia (OR = 2.4; 95% CI, 1.1-5.1) and systolic hypotension (OR 7.0; 95% CI: 2.4-20.4). Conclusions: Sepsis and severe sepsis carry high mortality among hospitalised adults in Malawi. Measures to reduce this, including early identification and targeted intervention in high-risk patients, especially HIV-positive individuals recently commenced on ART, are urgently required

    Neutron skin of 208^{208}Pb from Coherent Pion Photoproduction

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    Information on the size and shape of the neutron skin on 208^{208}Pb has been extracted from coherent pion photoproduction cross sections measured using the Crystal Ball together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections the half-height radius and diffuseness of the neutron distribution are found to be 6.70±0.03(stat)\pm 0.03(stat) fm and 0.55±0.01(stat)\pm 0.01(stat)−0.03+0.02(sys)^{+0.02}_{-0.03}(sys) fm respectively, corresponding to a neutron skin thickness Δrnp\Delta r_{np}=0.15±0.03(stat)\pm 0.03(stat)−0.03+0.01(sys)^{+0.01}_{-0.03}(sys) fm. The results give the first successful extraction of a neutron skin with an electromagnetic probe and indicate the skin of 208^{208}Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.Comment: 4 figures 5 pages. Version submitted to journal. Includes additional studies of systematic effects in the extracted diffuseness, which led to a small increase in the quoted systematic error. These additional studies are discussed in the revised manuscript. Also includes minor editorial improvements to the tex

    Determination of the Dalitz plot parameter alpha for the decay eta->3pi^0 with the Crystal Ball at MAMI-B

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    A precise measurement of the Dalitz plot parameter, alpha, for the eta->3pi^0 decay is presented. The experiment was performed with the Crystal Ball and TAPS large acceptance photon detectors at the tagged photon beam facility of the MAMI-B electron accelerator in Mainz. High statistics of 1.8*10^6 eta->3pi^0 events were obtained, giving the result alpha = -0.032 +/- 0.002(stat) +/- 0.002(syst).Comment: 9 pages, 6 figures, published in the online-first section of EPJ A, included changes referees asked for, added DO

    Photoproduction of π0\pi^0-pairs off protons and off neutrons

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    Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of π0π0\pi^0\pi^0 pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557~MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400~MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15\%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance region (final state invariant masses up to ≈\approx1550~MeV), where both reactions are dominated by the N(1520)3/2−→Δ(1232)3/2+πN(1520)3/2^-\rightarrow \Delta(1232)3/2^+\pi decay. At higher energies, angular and invariant-mass distributions are different. A simple analysis of the shapes of the invariant-mass distributions in the third resonance region is consistent with strong contributions of an N⋆→NσN^{\star}\rightarrow N\sigma decay for the proton, while the reaction is dominated by a sequential decay via a Δπ\Delta\pi intermediate state for the neutron. The data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled channel analysis.Comment: accepted for publication in Eur. Phys. J.
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