35,259 research outputs found

    Organic farming and agri-environmental stewardship schemes in Devon

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    A postal survey was undertaken in North Devon looking at entry into England Rural Development Programme (ERDP) environmental schemes in relation to farming system and markets. The main survey was based in and around the North Devon Biosphere reserve. Significantly more farms replied who had Countryside Stewardship (CSS) agreements than from those who were not in the scheme. There was a greater likelihood of small farms joining CSS as were beef, sheep and cereal farms compared with dairy farms. A greater percent of organic farms had CSS agreements compared with the conventional farms. A smaller telephone survey in a CSS target area in South Devon was also undertaken which confirmed these results. Those farms with CSS agreements were more likely to have joined or be joining the new agri-environmental schemes

    Saddlepoint approximation for moment generating functions of truncated random variables

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    We consider the problem of approximating the moment generating function (MGF) of a truncated random variable in terms of the MGF of the underlying (i.e., untruncated) random variable. The purpose of approximating the MGF is to enable the application of saddlepoint approximations to certain distributions determined by truncated random variables. Two important statistical applications are the following: the approximation of certain multivariate cumulative distribution functions; and the approximation of passage time distributions in ion channel models which incorporate time interval omission. We derive two types of representation for the MGF of a truncated random variable. One of these representations is obtained by exponential tilting. The second type of representation, which has two versions, is referred to as an exponential convolution representation. Each representation motivates a different approximation. It turns out that each of the three approximations is extremely accurate in those cases ``to which it is suited.'' Moreover, there is a simple rule of thumb for deciding which approximation to use in a given case, and if this rule is followed, then our numerical and theoretical results indicate that the resulting approximation will be extremely accurate.Comment: Published at http://dx.doi.org/10.1214/009053604000000689 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

    The structural response of unsymmetrically laminated composite cylinders

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    The responses of an unsymmetrically laminated fiber-reinforced composite cylinder to an axial compressive load, a torsional load, and the temperature change associated with cooling from the processing temperature to the service temperature are investigated. These problems are considered axisymmetric and the response is studied in the context of linear elastic material behavior and geometrically linear kinematics. Four different laminates are studied: a general unsymmetric laminate; two unsymmetric but more conventional laminates; and a conventional quasi-isotropic symmetric laminate. The responses based on closed-form solutions for different boundary conditions are computed and studied in detail. Particular emphasis is directed at understanding the influence of elastic couplings in the laminates. The influence of coupling decreased from a large effect in the general unsymmetric laminate, to practically no effect in the quasi-isotropic laminate. For example, the torsional loading of the general unsymmetric laminate resulted in a radial displacement. The temperature change also caused a significant radial displacement to occur near the ends of the cylinder. On the other hand, the more conventional unsymmetric laminate and the quasi-isotropic cylinder did not deform radially when subjected to a torsional load. From the results obtained, it is clear the degree of elastic coupling can be controlled and indeed designed into a cylinder, the degree and character of the coupling being dictated by the application

    Previously unpublished Odonata records from Sarawak, Borneo : part 2, Kubah National Park

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    Records of Odonata from Kubah National Park, near Kuching in west Sarawak, are presented. Eighty-five species are known from the national park. Notable records include Drepanosticta drusilla, Rhinocypha species cf spinifer, Bornagriolestes species, Anaciaeschna species and Macromidia genialis erratica

    A MERLIN Observation of PSR B1951+32 and its associated Plerion

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    In an investigative 16 hour L band observation using the MERLIN radio interferometric array, we have resolved both the pulsar PSR B1951+32 and structure within the flat spectral radio continuum region, believed to be the synchrotron nebula associated with the interaction of the pulsar and its `host' supernova remnant CTB 80. The extended structure we see, significant at ∼\sim 4.5 σ\sigma, is of dimensions 2.5" ×\times 0.75", and suggests a sharp bow shaped arc of shocked emission, which is correlated with similar structure observed in lower resolution radio maps and X-ray images. Using this MERLIN data as a new astrometric reference for other multiwavelength data we can place the pulsar at one edge of the HST reported optical synchrotron knot, ruling out previous suggested optical counterparts, and allowing an elementary analysis of the optical synchrotron emission which appears to trail the pulsar. The latter is possibly a consequence of pulsar wind replenishment, and we suggest that the knot is a result of magnetohydrodynamic (MHD) instabilities. These being so, it suggests a dynamical nature to the optical knot, which will require high resolution optical observations to confirm.Comment: 12 pages, 2 figures. Accepted for publication in ApJ

    Methods of preparing spectrographically pure praseodymium salts

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    An ion-exchange process was developed for the separation of spectrographically pure praseodymium salts in kilogram amounts from commercially available concentrates. The application of either 0.5% or 0.1% citrate solutions as eluting agents was show to result in excellent separations of praseodymium from samarium, neodymium, and lanthanum when the mixed rare earths were eluted from Amberlite IR-100 or Nalcite HCR cation-exchange resins
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