736 research outputs found

    Phylogenetic Analysis and Rapid Identification of the Whitefly, Bemisia afer, in China

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    The phylogenetic relationship between the whitefly Bemisia afer (Priesner & Hosny) (Hemiptera: Aleyrodidae) from China and other populations among the world were analyzed based on the mitochondrial cytochrome oxidase I (mtCOI) gene. Phylogenetic analysis of mtCOI sequences and those of reference B. afer sequences showed that the populations of the species could be separated into 5 clades (I–V). There were at least two clades of the species from China (IV and V). These data suggested that B. afer might be a species complex. The Chinese B. afer populations were most divergent with B. afer from the United Kingdom and African countries. The distance between the Chinese B. afer (IV and V) and clades I, II, and III is more than 32%, while the distance among clades I, II, III is lower than 7.7%. A new set of primers specific to B. afer was designed to amplify a region of approximately 400 bp to discriminate B. afer from other Bemisia species in China based on mtCOI sequences

    RAMESES publication standards: realist syntheses

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    PMCID: PMC3558331This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

    A Decade of SN1993J: Discovery of Wavelength Effects in the Expansion Rate

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    We have studied the growth of the shell-like radio structure of supernova SN1993J in M81 from September 1993 through October 2003 with very-long-baseline interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18cm. For this purpose, we have developed a method to accurately determine the outer radius (R) of any circularly symmetric compact radio structure like SN1993J. The source structure of SN1993J remains circularly symmetric (with deviations from circularity under 2%) over almost 4000 days. We characterize the decelerated expansion of SN 1993J through approximately day 1500 after explosion with an expansion parameter m=0.845±0.005m= 0.845\pm0.005 (R∝tmR \propto t^{m}). However, from that day onwards the expansion is different when observed at 6 and 18cm. Indeed, at 18cm, the expansion can be well characterized by the same mm as before day 1500, while at 6cm the expansion appears more decelerated, and is characterized by another expansion parameter, m6=0.788±0.015m_{6}= 0.788\pm0.015. Therefore, since about day 1500 on, the radio source size has been progressively smaller at 6cm than at 18cm. These findings are in stark contrast to previous reports by other authors on the details of the expansion. In our interpretation the supernova expands with a single expansion parameter, m=0.845±0.005m= 0.845\pm0.005, and the 6cm results beyond day 1500 are due to physical effects, perhaps also coupled to instrumental limitations. Two physical effects may be involved: (a) a changing opacity of the ejecta to the 6cm radiation, and (b) a radial decrease of the magnetic field in the emitting region. (Long abstract cut. Please, read full abstract in manuscript).Comment: 21 pages, 19 figures, accepted in A&

    Nonequilibrium Evolution of Correlation Functions: A Canonical Approach

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    We study nonequilibrium evolution in a self-interacting quantum field theory invariant under space translation only by using a canonical approach based on the recently developed Liouville-von Neumann formalism. The method is first used to obtain the correlation functions both in and beyond the Hartree approximation, for the quantum mechanical analog of the Ο•4\phi^{4} model. The technique involves representing the Hamiltonian in a Fock basis of annihilation and creation operators. By separating it into a solvable Gaussian part involving quadratic terms and a perturbation of quartic terms, it is possible to find the improved vacuum state to any desired order. The correlation functions for the field theory are then investigated in the Hartree approximation and those beyond the Hartree approximation are obtained by finding the improved vacuum state corrected up to O(Ξ»2){\cal O}(\lambda^2). These correlation functions take into account next-to-leading and next-to-next-to-leading order effects in the coupling constant. We also use the Heisenberg formalism to obtain the time evolution equations for the equal-time, connected correlation functions beyond the leading order. These equations are derived by including the connected 4-point functions in the hierarchy. The resulting coupled set of equations form a part of infinite hierarchy of coupled equations relating the various connected n-point functions. The connection with other approaches based on the path integral formalism is established and the physical implications of the set of equations are discussed with particular emphasis on thermalization.Comment: Revtex, 32 pages; substantial new material dealing with non-equilibrium evolution beyond Hartree approx. based on the LvN formalism, has been adde

    When Can Antibiotic Treatments for Trachoma Be Discontinued? Graduating Communities in Three African Countries

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    Trachoma, the major cause of infectious blindness in the world, occurs when repeated infections of the ocular strains of Chlamydia trachomatis lead to a cascade of conjunctival scarring, in-turned eyelids and eyelashes, and eventually blindness due to corneal opacity. To reduce the prevalence of infection, the World Health Organization (WHO) advocates at least three annual community-wide distributions of oral antibiotics in affected areas. This approach has proven effective, but there is room to explore other treatment strategies which reduce the use of antibiotics. Here, we used mathematical models and data from three trachoma-endemic countries (Tanzania, The Gambia, and Ethiopia) to analyze different treatment strategies. In the simulations, we show that a graduation strategy can reduce antibiotic distributions more than 2-fold in moderately affected areas. Both treatment strategies provide favorable results in reducing the prevalence of ocular chlamydia, but high costs and the potential for resistance are important issues to consider when administering mass doses of antibiotics

    Genome-wide association analysis identifies novel loci for chronotype in 100,420 individuals from the UK Biobank

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    Our sleep timing preference, or chronotype, is a manifestation of our internal biological clock. Variation in chronotype has been linked to sleep disorders, cognitive and physical performance, and chronic disease. Here we perform a genome-wide association study of self-reported chronotype within the UK Biobank cohort (n=100,420). We identify 12 new genetic loci that implicate known components of the circadian clock machinery and point to previously unstudied genetic variants and candidate genes that might modulate core circadian rhythms or light-sensing pathways. Pathway analyses highlight central nervous and ocular systems and fear-response-related processes. Genetic correlation analysis suggests chronotype shares underlying genetic pathways with schizophrenia, educational attainment and possibly BMI. Further, Mendelian randomization suggests that evening chronotype relates to higher educational attainment. These results not only expand our knowledge of the circadian system in humans but also expose the influence of circadian characteristics over human health and life-history variables such as educational attainment

    Importance of Coverage and Endemicity on the Return of Infectious Trachoma after a Single Mass Antibiotic Distribution

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    Trachoma, caused by ocular chlamydia infection, is the most common infectious cause of blindness in the world. The World Health Organization (WHO) recommends the SAFE strategy (eyelid surgery, antibiotics, facial hygiene, environmental improvements) for trachoma control. Oral antibiotics reduce the transmission of ocular chlamydia, but re-infection of treated individuals is common. Therefore, the WHO recommends annual mass antibiotic treatments to the entire village. The success of treatment is likely based on many factors, including the antibiotic coverage, or percentage of villagers who receive antibiotics. However, no studies have analyzed the importance of antibiotic coverage for the reduction of ocular chlamydia. Here, we performed multivariate regression analyses on data from a clinical trial of mass oral antibiotics for trachoma in a severely affected area of Ethiopia. At the relatively high levels of antibiotic coverage in our study, coverage was associated with post-treatment infection at two months, but not at six months. The amount of infection at baseline was strongly correlated with post-treatment infection at both two and six months. These results suggest that in areas with severe trachoma treated with relatively high antibiotic coverage, increasing coverage even further may have only a short-term benefit
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