471 research outputs found

    Population dynamics of Windermere perch

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    This paper looks briefly at some of the more recent analyses and interpretations of the changes that have occurred in the population dynamics of Windermere perch and at the present level of understanding. The long-term study has shown how flexible the population is and how it has behaved in different ways over successive periods of time since 1939. Through one of these periods it was possible to account for nearly all the variance in recruitment by a relatively simple explanatory model. The reduction in numbers on the outbreak of disease in 1976 started a natural experiment which will form a baseline for future studies

    Sustainable fish production in Lake Nasser: ecological basis and management policy

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    The aim of the Lake Nasser Project is to integrate social, economic, and ecological factors in the formulation of a management policy for sustainable fish production. The workshop was held to review the present state of knowledge, identify constraints, evaluate existing information and state of the art techniques, and determine future research objectives and strategy.Lake fisheries, Fishery management, Artificial lakes, Nasser Lake, Egypt, Arab. Rep.,

    Comparison of Theoretical and Experimental Bending and Torsional Moments of Endodontic Files and Reamers

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67347/2/10.1177_00220345670460051101.pd

    Keep it simple: three indicators to deal with overfishing

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    Three simple fisheries indicators are presented: (i) percentage of mature fish in catch, with 100% as target; (ii) percent of specimens with optimum length in catch, with 100% as target; and (iii) percentage of ‘mega-spawners‘ in catch, with 0% as target, and 30–40% as representative of reasonable stock structure if no upper size limit exists. Application of these indicators to stocks of Gadus morhua, Sardinella aurita and Epinephelus aeneus demonstrate their usefulness. It is argued that such simple indicators have the potential to allow more stakeholders such as fishers, fish dealers, supermarket managers, consumers and politicians to participate in fisheries management and eventually hold and reverse the global pattern of convenience overfishing, which is defined here as deliberate overfishing sanctioned by official bodies who find it more convenient to risk eventual collapse of fish stocks than to risk social and political conflicts

    Gradient test for generalised linear models with random effects

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    This work develops the gradient test for parameter selection in generalised linear models with random effects. Asymptotically, the test statistic has a chi-squared distribution and the statistic has a compelling feature: it does not require computation of the Fisher information matrix. Performance of the test is verified through Monte Carlo simulations of size and power, and also compared to the likelihood ratio, Wald and Rao tests. The gradient test provides the best results overall when compared to the traditional tests, especially for smaller sample sizes

    Three-slit experiments and quantum nonlocality

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    An interesting link between two very different physical aspects of quantum mechanics is revealed; these are the absence of third-order interference and Tsirelson's bound for the nonlocal correlations. Considering multiple-slit experiments - not only the traditional configuration with two slits, but also configurations with three and more slits - Sorkin detected that third-order (and higher-order) interference is not possible in quantum mechanics. The EPR experiments show that quantum mechanics involves nonlocal correlations which are demonstrated in a violation of the Bell or CHSH inequality, but are still limited by a bound discovered by Tsirelson. It now turns out that Tsirelson's bound holds in a broad class of probabilistic theories provided that they rule out third-order interference. A major characteristic of this class is the existence of a reasonable calculus of conditional probability or, phrased more physically, of a reasonable model for the quantum measurement process.Comment: 9 pages, no figur

    Surface Roughness and Effective Stick-Slip Motion

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    The effect of random surface roughness on hydrodynamics of viscous incompressible liquid is discussed. Roughness-driven contributions to hydrodynamic flows, energy dissipation, and friction force are calculated in a wide range of parameters. When the hydrodynamic decay length (the viscous wave penetration depth) is larger than the size of random surface inhomogeneities, it is possible to replace a random rough surface by effective stick-slip boundary conditions on a flat surface with two constants: the stick-slip length and the renormalization of viscosity near the boundary. The stick-slip length and the renormalization coefficient are expressed explicitly via the correlation function of random surface inhomogeneities. The effective stick-slip length is always negative signifying the effective slow-down of the hydrodynamic flows by the rough surface (stick rather than slip motion). A simple hydrodynamic model is presented as an illustration of these general hydrodynamic results. The effective boundary parameters are analyzed numerically for Gaussian, power-law and exponentially decaying correlators with various indices. The maximum on the frequency dependence of the dissipation allows one to extract the correlation radius (characteristic size) of the surface inhomogeneities directly from, for example, experiments with torsional quartz oscillators.Comment: RevTeX4, 14 pages, 3 figure

    Hsp70 in mitochondrial biogenesis

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    The family of hsp70 (70 kilodalton heat shock protein) molecular chaperones plays an essential and diverse role in cellular physiology, Hsp70 proteins appear to elicit their effects by interacting with polypeptides that present domains which exhibit non-native conformations at distinct stages during their life in the cell. In this paper we review work pertaining to the functions of hsp70 proteins in chaperoning mitochondrial protein biogenesis. Hsp70 proteins function in protein synthesis, protein translocation across mitochondrial membranes, protein folding and finally the delivery of misfolded proteins to proteolytic enzymes in the mitochondrial matrix

    The Microhardness of Enamel and Dentin

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68055/2/10.1177_00220345580370041301.pd
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