13,339 research outputs found

    The measurement of velocity gradients in laminar flow by homodyne light-scattering spectroscopy

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    A technique for measuring velocity gradients in laminar flows by homodyne light scattering is presented. A theory which describes the light-scattering spectrum is derived that includes the effects of different types of linear flow fields, particle diffusion and the intensity profile in the scattering volume. The conditions which must be satisfied in order that the theory describe the experimental situation are outlined and complementary experiments are performed which both verify the theory and apply the technique. Verification is provided using the flow in a Couette device, and the flow due to single rotating cylinder in a large bath of fluid. The technique is then applied to measure the spatial variation of the shear rate in a four-roll mill

    The art of being human : a project for general philosophy of science

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    Throughout the medieval and modern periods, in various sacred and secular guises, the unification of all forms of knowledge under the rubric of ‘science’ has been taken as the prerogative of humanity as a species. However, as our sense of species privilege has been called increasingly into question, so too has the very salience of ‘humanity’ and ‘science’ as general categories, let alone ones that might bear some essential relationship to each other. After showing how the ascendant Stanford School in the philosophy of science has contributed to this joint demystification of ‘humanity’ and ‘science’, I proceed on a more positive note to a conceptual framework for making sense of science as the art of being human. My understanding of ‘science’ is indebted to the red thread that runs from Christian theology through the Scientific Revolution and Enlightenment to the Humboldtian revival of the university as the site for the synthesis of knowledge as the culmination of self-development. Especially salient to this idea is science‘s epistemic capacity to manage modality (i.e. to determine the conditions under which possibilities can be actualised) and its political capacity to organize humanity into projects of universal concern. However, the challenge facing such an ideal in the twentyfirst century is that the predicate ‘human’ may be projected in three quite distinct ways, governed by what I call ‘ecological’, ‘biomedical’ and ‘cybernetic’ interests. Which one of these future humanities would claim today’s humans as proper ancestors and could these futures co-habit the same world thus become two important questions that general philosophy of science will need to address in the coming years

    Deer reduce habitat quality for a woodland songbird: evidence from settlement patterns, demographic parameters, and body condition.

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    Understanding avian responses to ungulate-induced habitat modification is important because deer populations are increasing across much of temperate Europe and North America. Our experimental study examined whether habitat quality for Blackcaps (Sylvia atricapilla) in young woodland in eastern England was affected by deer, by comparing Blackcap behavior, abundance, and condition between paired plots (half of each pair protected from deer). The vegetation in each pair of plots was the same age. The Blackcap is an ideal model species for testing effects of deer on avian habitat quality because it is dependent on dense understory vegetation and is abundant throughout much of Europe. We compared timing of settlement, abundance, age structure (second-year vs. after-second-year), and phenotypic quality (measured as a body condition index, body mass divided by tarsus length) between experimental and control plots. We used point counts to examine Blackcap distribution, and standardized mist netting to collect demographic and biometric data. Incidence of singing Blackcaps was higher in nonbrowsed than in browsed plots, and singing males were recorded in nonbrowsed plots earlier in the season, indicating earlier and preferential territory establishment. Most Blackcaps, both males and females, were captured in vegetation prior to canopy closure (2–4 years of regrowth). Body condition was superior for male Blackcaps captured in nonbrowsed plots; for second-year males this was most marked in vegetation prior to canopy closure. We conclude that deer browsing in young woodland can alter habitat quality for understory-dependent species, with potential consequences for individual fitness and population productivity beyond the more obvious effects on population density

    Neutrino-Neutrino Scattering and Matter-Enhanced Neutrino Flavor Transformation in Supernovae

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    We examine matter-enhanced neutrino flavor transformation (ντ(μ)νe\nu_{\tau(\mu)}\rightleftharpoons\nu_e) in the region above the neutrino sphere in Type II supernovae. Our treatment explicitly includes contributions to the neutrino-propagation Hamiltonian from neutrino-neutrino forward scattering. A proper inclusion of these contributions shows that they have a completely negligible effect on the range of νe\nu_e-ντ(μ)\nu_{\tau(\mu)} vacuum mass-squared difference, δm2\delta m^2, and vacuum mixing angle, θ\theta, or equivalently sin22θ\sin^22\theta, required for enhanced supernova shock re-heating. When neutrino background effects are included, we find that rr-process nucleosynthesis from neutrino-heated supernova ejecta remains a sensitive probe of the mixing between a light νe\nu_e and a ντ(μ)\nu_{\tau(\mu)} with a cosmologically significant mass. Neutrino-neutrino scattering contributions are found to have a generally small effect on the (δm2, sin22θ)(\delta m^2,\ \sin^22\theta) parameter region probed by rr-process nucleosynthesis. We point out that the nonlinear effects of the neutrino background extend the range of sensitivity of rr-process nucleosynthesis to smaller values of δm2\delta m^2.Comment: 38 pages, tex, DOE/ER/40561-150-INT94-00-6

    Comparing Methods to Extract the Knowledge from Neural Networks

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    Neural networks (NN) have been shown to be accurate classifiers in many domains. Unfortunately, the lack of NN’s explanatory capability of knowledge learned has somewhat limited their application. A stream of research has therefore developed focusing on knowledge extraction from within neural networks. The literature, unfortunately, lacks consensus on how best to extract knowledge from help neural networks. Additionally, there is a lack of empirical studies that compare existing algorithms on relevant performance measures. Therefore, this study attempts to help fill this gap by comparing two different approaches to extracting IF-THEN rules from feedforward NN. The results show a significant difference in the performance of the two algorithms depending on the structure of the dataset utilized

    A methodological approach to the study of archaeological cereal meals: a case study at Çatalhöyük East (Turkey)

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    This paper presents an integrated methodology for the analysis of archaeological remains of cereal meals, based on scanning electronic microscopic analyses of microstructures of charred food fragments from Neolithic Çatalhöyük (Turkey). The remains of cereal foods as ‘bread-like’ or ‘porridge-like’ small charred lumps of various amalgamated plant materials are frequently recovered from Neolithic and later archaeological sites in southwest Asia and Europe. Cereal food remains have recently attracted interest because the identification of their plant contents, the forms of food that they represent and the methods used in their creation can provide unique information about ancient culinary traditions and routine food processing, preparation and cooking techniques. Here, we focus on three methodological aspects: (1) the analysis of their composition; (2) the analysis of their microstructure to determine preparation and cooking processes; (3) the comparison with experimental reference materials. Preliminary results are presented on the botanical composition and cooking processes represented by the charred cereal preparations found at Neolithic Çatalhöyük (Turkey), for example cereals processed into bread, dough and/or porridge

    How Much Longer Will it Take? A Ten-year Review of the Implementation of United Nations General Assembly Resolutions 61/105, 64/72 and 66/68 on the Management of Bottom Fisheries in Areas Beyond National Jurisdiction

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    The United Nations General Assembly (UNGA) in 2002 adopted the first in a series of resolutions regarding the conservation of biodiversity in the deep sea. Prompted by seriousconcerns raised by scientists, non-governmental organizations (NGOs) and numerous States,these resolutions progressively committed States to act both individually and through regional fishery management organizations (RFMOs) to either manage bottom fisheries in areas beyond national jurisdiction to prevent significant adverse impacts on deep-sea species, ecosystems and biodiversity or else prohibit bottom fishing from taking place.Ten years have passed since the adoption of resolution 61/105 in 2006, calling on States to take a set of specific actions to manage bottom fisheries in areas beyond national jurisdiction to protect vulnerable marine ecosystems (VMEs) from the adverse impacts of bottom fishing and ensure the sustainability of deep-sea fish stocks. Despite the considerable progress by some RFMOs, there remain significant gaps in the implementation of key elements and commitments in the resolutions. The Deep Sea Conservation Coalition (DSCC) has prepared this report to assist the UNGA in its review in 2016 and to address the following question: How effectively have the resolutions been implemented

    MSW-like Enhancements without Matter

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    We study the effects of a scalar field, coupled only to neutrinos, on oscillations among weak interaction current eigenstates. The effect of a real scalar field appears as effective masses for the neutrino mass eigenstates, the same for \nbar as for \n. Under some conditions, this can lead to a vanishing of δm2\delta m^2, giving rise to MSW-like effects. We discuss some examples and show that it is possible to resolve the apparent discrepancy in spectra required by r-process nucleosynthesis in the mantles of supernovae and by Solar neutrino solutions.Comment: 9 pages, latex, 1 figur

    Unfinished Business: a Review of the Implementation of the Provisions of United Nations General Assembly Resolutions 61/105 and 64/72, Related to the Management of Bottom Fisheries in Areas Beyond National Jurisdiction

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    In 2006 the General Assembly adopted resolution 61/105, based on a compromise proposal offered by deep-sea fishing nations, which committed States and regional fisheries management organisations [RFMOs] to take specific measures to protect vulnerable marine ecosystems [VMEs] from the adverse impacts of bottom fisheries in the high seas and to ensure the longterm sustainability of deep-sea fish stocks. These measures included conducting impact assessments to determine whether significant adverse impacts[SAIs] to VMEs would occur, managing fisheries to prevent SAIs on VMEs, and closing areas of the high seas to bottom fishing where VMEs are known or likely to occur, unless regulations are in place to prevent SAIs and to manage sustainably deep-sea fish stocks. Based on a review in 2009 of the actions taken by States and RFMOS, the UNGA adoptedresolution 64/72 that reaffirmed resolution 61/105 and strengthened the call for action through committing States, inter alia, to ensure that vessels do not engage in bottom fishing until impact assessments have been carried out and to not authorise bottom fishing activities until the measures in resolutions 64/72 and 61/105 have been adopted andimplemented
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