5,491 research outputs found

    The Effect of Agricultural Practices on a Dairy Farm on Nitrate Leaching to 1m

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    Dairy farms, in Ireland, carry the highest stock densities and use the highest rates of fertiliser nitrogen (N). They constitute the highest risk of nitrate leaching, especially where soils are thin or free-draining. The effect of 4 grass managements on leaching was studied on a dairy farm having free-draining soils overlying Karst limestone. This was a new, farm-comprehensive approach to nitrate leaching which had not been carried out previously

    Against strong pluralism

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    Strong pluralists hold that not even permanent material coincidence is enough for identity. Strong pluralism entails the possibility of purely material objects -- even if not coincident -- alike in all general respects, categorial and dispositional, relational and non-relational, past, present and future, at the microphysical level, but differing in some general modal, counterfactual or dispositional repscts at the macrophysical level. It is objectionable because it thus deprives us of the explanatory resources to explain why evident absurdities are absurd. A second objection is to the suggestion that cases involving artefacts can illustrate strong pluralism. This offends against the principle that gien a complex intrinsic microphysical property instantiated in some regiion, the number of material things possessing it in that region cannot depend on the existence and nature of intentional activity taking place outside it

    Temperature dependence of surface reconstructions of Au on Pd(110)

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    Surface reconstructions of Au film on Pd(110) substrate are studied using a local Einstein approximation to quasiharmonic theory with the Sutton-Chen interatomic potential. Temperature dependent surface free energies for different coverages and surface structures are calculated. Experimentally observed transformations from (1×1)(1\times1) to (1×2)(1 \times 2) and (1×3)(1 \times 3) structures can be explained in the framework of this model. Also conditions for Stranski-Krastanov growth mode are found to comply with experiments. The domain of validity of the model neglecting mixing entropy is analyzed.Comment: 7 pages, REVTeX two-column format, 3 postscript figures available on request from [email protected] To appear in Phys. Rev. Letter

    A Characterisation of Strong Wave Tails in Curved Space-Times

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    A characterisation of when wave tails are strong is proposed. The existence of a curvature induced tail (i.e. a Green's function term whose support includes the interior of the light-cone) is commonly understood to cause backscattering of the field governed by the relevant wave equation. Strong tails are characterised as those for which the purely radiative part of the field is backscattered. With this definition, it is shown that electromagnetic waves in asymptotically flat space-times and fields governed by tail-free propagation have weak tails, but minimally coupled scalar fields in a cosmological scenario have strong tails.Comment: 17 pages, Revtex, to appear in Classical and Quantum Gravit

    Optimizing tuning masses for helicopter rotor blade vibration reduction including computed airloads and comparison with test data

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    The development and validation of an optimization procedure to systematically place tuning masses along a rotor blade span to minimize vibratory loads are described. The masses and their corresponding locations are the design variables that are manipulated to reduce the harmonics of hub shear for a four-bladed rotor system without adding a large mass penalty. The procedure incorporates a comprehensive helicopter analysis to calculate the airloads. Predicting changes in airloads due to changes in design variables is an important feature of this research. The procedure was applied to a one-sixth, Mach-scaled rotor blade model to place three masses and then again to place six masses. In both cases the added mass was able to achieve significant reductions in the hub shear. In addition, the procedure was applied to place a single mass of fixed value on a blade model to reduce the hub shear for three flight conditions. The analytical results were compared to experimental data from a wind tunnel test performed in the Langley Transonic Dynamics Tunnel. The correlation of the mass location was good and the trend of the mass location with respect to flight speed was predicted fairly well. However, it was noted that the analysis was not entirely successful at predicting the absolute magnitudes of the fixed system loads

    Spherically Symmetric Solutions in Macroscopic Gravity

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    Schwarzschild's solution to the Einstein Field Equations was one of the first and most important solutions that lead to the understanding and important experimental tests of Einstein's theory of General Relativity. However, Schwarzschild's solution is essentially based on an ideal theory of gravitation, where all inhomogeneities are ignored. Therefore, any generalization of the Schwarzschild solution should take into account the effects of small perturbations that may be present in the gravitational field. The theory of Macroscopic Gravity characterizes the effects of the inhomogeneities through a non-perturbative and covariant averaging procedure. With similar assumptions on the geometry and matter content, a solution to the averaged field equations as dictated by Macroscopic Gravity are derived. The resulting solution provides a possible explanation for the flattening of galactic rotation curves, illustrating that Dark Matter is not real but may only be the result of averaging inhomogeneities in a spherically symmetric background.Comment: 14 pages, added and updated references, some paragraphs rewritten for clarity, typographical errors fixed, results have not change

    Spatial and temporal arrival patterns of Madagascar's vertebrate fauna explained by distance, ocean currents, and ancestor type

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    How, when, and from where Madagascar's vertebrates arrived on the island is poorly known, and a comprehensive explanation for the distribution of its organisms has yet to emerge. We begin to break that impasse by analyzing vertebrate arrival patterns implied by currently existing taxa. For each of 81 clades, we compiled arrival date, source, and ancestor type (obligate freshwater, terrestrial, facultative swimmer, or volant). We analyzed changes in arrival rates, with and without adjusting for clade extinction. Probability of successful transoceanic dispersal is negatively correlated with distance traveled and influenced by ocean currents and ancestor type. Obligate rafters show a decrease in probability of successful transoceanic dispersal fromthe Paleocene onward, reaching the lowest levels after the mid- Miocene. This finding is consistent with a paleoceanographic model [Ali JR, HuberM(2010) Nature 463:653-656] that predicts Early Cenozoic surface currents periodically conducive to rafting or swimming fromAfrica, followed by a reconfiguration to present-day flow15-20 million years ago that significantly diminished the ability for transoceanic dispersal to Madagascar from the adjacent mainland
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