129,211 research outputs found

    Fish assemblages and indicator species: reef fishes off the southeastern United States

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    For many fish stocks, resource management cannot be based on stock assessment because data are insufficient-a situation that requires alternative approaches to management. One possible approach is to manage data-limited stocks as part of an assemblage and to determine the status of the entire unit by a data-rich indicator species. The utility of this approach was evaluated in analyses of 15 years of commercial and 34 years of recreational logbook data from reef fisheries off the southeastern United States coast. Multivariate statistical analyses successfully revealed three primary assemblages. Within assemblages, however, there was little evidence of synchrony in population dynamics of member species, and thus, no support for the use of indicator species. Nonetheless, assemblages could prove useful as management units. Their identification offers opportunities for implementing management to address such ecological considerations as bycatch and species interrelations

    Elastic and inelastic scattering of 40 eV electrons from atomic lead

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    Differential and integral electron impact cross sections for elastic scattering and for the excitation of the first five states in lead have been determined at 40 eV impact energy. The cross section measurements were placed on the absolute scale by normalizing to the optical f-value of the 6p7s3P1 transition which is the upper state for the 7229 Å, 4057 Å and 3639 Å laser emissions. The integral cross sections for elastic scattering (6p2 3P0) and for the excitation of the 6p2 3P1, 6p2 3P2, 6p2 1D2, and 6p7s 3P0(+6p7s3P1) states are: 44, 0.15, 1.5, 0.05 and 8.4*10^-16 cm^2 respectively

    Unimodular integer circulants associated with trinomials

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    The n � n circulant matrix associated with the polynomial [image removed] (with d < n) is the one with first row (a0 ? ad 0 ? 0). The problem as to when such circulants are unimodular arises in the theory of cyclically presented groups and leads to the following question, previously studied by Odoni and Cremona: when is Res(f(t), tn-1) = �1? We give a complete answer to this question for trinomials f(t) = tm � tk � 1. Our main result was conjectured by the author in an earlier paper and (with two exceptions) implies the classification of the finite Cavicchioli?Hegenbarth?Repov? generalized Fibonacci groups, thus giving an almost complete answer to a question of Bardakov and Vesnin

    Behaviour of FRP-to-concrete bonded joints

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    The bond behaviour between FRP (fibre-reinforced polymer) and concrete is a consideration in the design of FRP strengthening mechanisms for structurally deficient or functionally obsolete concrete structures. In the past, a number of empirical models and fracture mechanics based theoretical models have been proposed for determining the effective bond length and bond strength of FRP sheets/plates bonded to concrete. However, these methods have yielded large discrepancies in the predictions of effective bond length and bond strength. In this paper, the results of an experimental investigation into effective bond length and bond strength are presented. Comparison of experiments results with predictions from three empirical and three fracture mechanics based theoretical models shows that a recently proposed fracture mechanics based local-bond slip model provides a conservative prediction of the effective bond length and an accurate prediction of bond strengt

    THE CASE OF U.S. MEAT EXPORTS

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    International Relations/Trade, Livestock Production/Industries,

    Distribution anisotropy: the influence of magnetic interactions on the anisotropy of magnetic remanence

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    The anisotropy of magnetic remanence (AMR) is often used as a tool for examining magnetic anisotropy of rocks. However, the influence of magnetostatic interactions on AMR has not been previously rigorously addressed either theoretically or experimentally, though it is widely thought to be highly significant. Using a three-dimensional micromagnetic algorithm, we have conducted a systematic numerical study of the role of magnetostatic interactions on AMR. We have considered both lineation and foliation, by modelling assemblages of ideal single domain grains and magnetically non-uniform magnetite-like cubic grains. We show that magnetostatic interactions strongly affect the measured AMR signal. It is found that depending on the orientation of the single-grain anisotropy and grain spacing it is possible for the AMR signal from a chain or grid of grains to be either oblate or prolate. For non-uniform grains, the degree of anisotropy generally increases with increasing interactions. In the modelling of AMR anisotropy, saturation isothermal remanence was chosen for numerical tractability. The influence of interactions on other types of more commonly measured AMR, are considered in light of the results in this paper. © The Geological Society of London 2004.Accepted versio

    Federal Non-defense Expenditures - Their Shifting Impact on the Regional Distribution of Income

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    Federal non-defense expenditure programs analyzed for impact on regional income distributio

    Commercialising Australia's interstate rail freight transport: Some ownership and investment issues

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    The paper addresses the issues of rights of way ownership and application of consistent investment appraisal techniques across modes of transport. There are linkages between ownership, rights of way, competitive strategies and market contestability which will have a significant bearing on the choice of investment criteria used by commercialised railways. Investment methodologies in competing modes of land transport must be consistent. Investment in individual elements of railway infrastructure must be integrated with the overall cost recovery strategy of the operator. Major railway projects must be submitted to both financial and economic evaluation, so that the interests of individual railway authorities and the community are considered

    Liquid-cooled liner for helmets

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    Liner acts as coolant tubing, manifold, and supporting structures. Fabric of waffle-design is made of several integrated channels (or capillaries) through which coolant liquid can flow. Thin and light-weight liner can be incorporated into any type of helmet or head gear
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