5,448 research outputs found

    'Bunchy top symptom' of papaya in Cuba: new insights

    Get PDF
    Papaya is an important export crop in Cuba. A disease named Bunchy top symptom (BTS) was first observed in 2003 from Villa Clara province, but is now widespread throughout the country. A nested PCR assay with 16S rDNA phytoplasma primers P1/P7 and R16F2n/R2 was used to index more than 2200 papaya plants, weeds and insect samples collected between November 2005 and June 2006. RFLP patterns for all amplicons were identical with HaeIII, RsaI and AluI enzymes. No rickettsia-like bacteria were found in any of the samples. Phytoplasma rDNA was amplified from 1449 (89.7%) papaya plants with BTS symptoms. Phytoplasma rDNA was also detected in 331 apparently healthy papayas, and other plant species: Anoda acerifolia (57), Euphorbia heterophylla (73), Malvastrum coromandelianum (41) and Rynchosia minima (37) and 60/75 batches of Empoasca papayae. Sequences from the phytoplasma in papaya (DQ868531), A. acerifolia (DQ286950); E. heterophylla (DQ286951); M. coromandelianum (DQ286952); R. minima (DQ868533) and the leafhopper E. papayae (DQ868532) all showed 99% similarity to the phytoplasma associated with polygala phyllody, PPhy, (AY787140) belonging to the 16SrII group, ‘Candidatus Phytoplasma aurantifolia’. The discovery of the BTS phytoplasma in weed species and a putative vector Empoasca papayae suggests, that these plants and the leafhopper may have role in the spread of this disease

    Evidence for a common physical description of non-Fermi-liquid behavior in f-electron systems

    Full text link
    The non-Fermi-liquid (NFL) behavior observed in the low temperature specific heat C(T)C(T) and magnetic susceptibility χ(T)\chi(T) of f-electron systems is analyzed within the context of a recently developed theory based on Griffiths singularities. Measurements of C(T)C(T) and χ(T)\chi(T) in the systems Th1xUxPd2Al3Th_{1-x}U_{x}Pd_{2}Al_{3}, Y1xUxPd3Y_{1-x}U_{x}Pd_3, and UCu5xMxUCu_{5-x}M_{x} (M = Pd, Pt) are found to be consistent with C(T)/Tχ(T)T1+λC(T)/T \propto \chi(T) \propto T^{-1+\lambda} predicted by this model with λ<1\lambda <1 in the NFL regime. These results suggest that the NFL properties observed in a wide variety of f-electron systems can be described within the context of a common physical picture.Comment: 4 pages, 4 figure

    Temperature effects on dislocation core energies in silicon and germanium

    Full text link
    Temperature effects on the energetics of the 90-degree partial dislocation in silicon and germanium are investigated, using non-equilibrium methods to estimate free energies, coupled with Monte Carlo simulations. Atomic interactions are described by Tersoff and EDIP interatomic potentials. Our results indicate that the vibrational entropy has the effect of increasing the difference in free energy between the two possible reconstructions of the 90-degree partial, namely, the single-period and the double-period geometries. This effect further increases the energetic stability of the double-period reconstruction at high temperatures. The results also indicate that anharmonic effects may play an important role in determining the structural properties of these defects in the high-temperature regime.Comment: 8 pages in two-column physical-review format with six figure

    Arsenic Exposure and Hypertension: A Systematic Review

    Get PDF
    Background: Environmental exposure to arsenic has been linked to hypertension in persons living in arsenic-endemic areas

    An instability criterion for nonlinear standing waves on nonzero backgrounds

    Full text link
    A nonlinear Schr\"odinger equation with repulsive (defocusing) nonlinearity is considered. As an example, a system with a spatially varying coefficient of the nonlinear term is studied. The nonlinearity is chosen to be repelling except on a finite interval. Localized standing wave solutions on a non-zero background, e.g., dark solitons trapped by the inhomogeneity, are identified and studied. A novel instability criterion for such states is established through a topological argument. This allows instability to be determined quickly in many cases by considering simple geometric properties of the standing waves as viewed in the composite phase plane. Numerical calculations accompany the analytical results.Comment: 20 pages, 11 figure

    Aerostructural Optimization of Nonplanar Lifting Surfaces

    Full text link
    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83557/1/AIAA-44727-830.pd

    Association between meniscal tears and the peak external knee adduction moment and foot rotation during level walking in postmenopausal women without knee osteoarthritis: a cross-sectional study

    Get PDF
    Introduction Meniscal injury is a risk factor for the development and progression of knee osteoarthritis, yet little is known about risk factors for meniscal pathology. Joint loading mediated via gait parameters may be associated with meniscal tears, and determining whether such an association exists was the aim of this study. Methods Three-dimensional Vicon gait analyses were performed on the dominant knee of 20 non-osteoarthritic women, and the peak external knee adduction moment during early and late stance was determined. The degree of foot rotation was also examined when the knee adductor moment peaked during early and late stance. Magnetic resonance imaging was used to determine the presence and severity of meniscal lesions in the dominant knee. Results The presence (P = 0.04) and severity (P = 0.01) of medial meniscal tears were positively associated with the peak external knee adduction moment during early stance while a trend for late stance was observed (P = 0.07). They were also associated with increasing degrees of internal foot rotation during late stance, independent of the magnitude of the peak external knee adduction moment occurring at that time (P = 0.03). During level walking among healthy women, the presence and severity of medial meniscal tears were positively associated with the peak external knee adduction moment. Moreover, the magnitude of internal foot rotation was associated with the presence and severity of medial meniscal lesions, independent of the peak knee adductor moment during late stance. Conclusion These data may suggest that gait parameters may be associated with meniscal damage, although longitudinal studies will be required to clarify whether gait abnormalities predate meniscal lesions, or vice versa, and therefore whether modification of gait patterns may be helpful

    Building confidence in projections of the responses of living marine resources to climate change

    Get PDF
    The Fifth Assessment Report of the Intergovernmental Panel on Climate Change highlights that climate change and ocean acidification are challenging the sustainable management of living marine resources (LMRs). Formal and systematic treatment of uncertainty in existing LMR projections, however, is lacking. We synthesize knowledge of how to address different sources of uncertainty by drawing from climate model intercomparison efforts. We suggest an ensemble of available models and projections, informed by observations, as a starting point to quantify uncertainties. Such an ensemble must be paired with analysis of the dominant uncertainties over different spatial scales, time horizons, and metrics. We use two examples: (i) global and regional projections of Sea Surface Temperature and (ii) projection of changes in potential catch of sablefish (Anoplopoma fimbria) in the 21st century, to illustrate this ensemble model approach to explore different types of uncertainties. Further effort should prioritize understanding dominant, undersampled dimensions of uncertainty, as well as the strategic collection of observations to quantify, and ultimately reduce, uncertainties. Our proposed framework will improve our understanding of future changes in LMR and the resulting risk of impacts to ecosystems and the societies under changing ocean conditions

    Non-Fermi liquid behavior and Griffiths phase in {\it f}-electron compounds

    Full text link
    We study the interplay among disorder, RKKY and Kondo interactions in {\it f}-electron alloys. We argue that the non-Fermi liquid behavior observed in these systems is due to the existence of a Griffiths phase close to a quantum critical point. The existence of this phase provides a unified picture of a large class of materials. We also propose new experiments that can test these ideas.Comment: 4 pages, 1 Figure. NEW version of the original manuscript. A single framework for NFL behavior in different kinds of alloys is presented. Final version finally allowed to appear on the glorious Physical Review Letter
    corecore