6,235 research outputs found

    Some solved and unsolved canonical problems of diffraction theory

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    Laser-Doppler gas-velocity instrument

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    Three-D instrument using a laser light source measures both turbulence and mean velocity of subsonic and supersonic gas flows. This instrument is based on the measurement of the Doppler frequency shift of light waves scattered by moving particles in the gas stream

    Sulphur and Carbon Isotopes as Tracers of Past Sub-seafloor Microbial Activity

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    Microbial life below the seafloor has changed over geological time, but these changes are often not obvious, as they are not recorded in the sediment. Sulphur (S) isotope values in pyrite extracted from a Plio- to Holocene sequence of the Peru Margin (Ocean Drilling Program, ODP, Site 1229) show a down-core pattern that correlates with the pattern of carbon (C) isotopes in diagenetic dolomite. Early formation of the pyrite is indicated by the mineralogical composition of iron, showing a high degree of pyritization throughout the sedimentary sequence. Hence, the S-record could not have been substantially overprinted by later pyrite formation. The S- and C-isotope profiles show, thus, evidence for two episodes of enhanced microbial methane production with a very shallow sulphate-methane transition zone. The events of high activity are correlated with zones of elevated organic C content in the stratigraphic sequence. Our results demonstrate how isotopic signatures preserved in diagenetic mineral phases provide information on changes of past biogeochemical activity in a dynamic sub-seafloor biosphere

    Graded Management Intensity of Grassland System for Enhancing Biodiversity on a Species and Landscape Scale

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    The objective of our research is to maintain and enhance wildlife resources, landscape diversity and economic competitiveness of grassland-ruminant systems. This may be accomplished by a diversified, graded management intensity of pastures and meadows (Dietl,1990), resulting in a network of intensively and extensively used grassland and other semi-natural habitats. Botanical diversity is thus increased on both a habitat and landscape level. In intensively farmed regions it may be necessary to re-establish species-rich grassland types and adjust management intensity to the site conditions and species’ requirements

    Laser Doppler velocity instrument

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    Laser Doppler velocity instrument for measuring turbulence and mean velocity in subsonic and supersonic gas flow

    Long Term Benefits of Diversified Forage-Oriented Cropping Systems as Compared to Rotations Based Mainly on Cereals or Maize

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    The aim of this study is to assess the long term effects of a forageoriented, versus a maize- and a cereal-oriented crop rotation on the yield potential and soil fertility, as well as the weed, disease and pest development. We report the results after four cropping cycles using silage maize (Zea mays L.) in 1994 and winter wheat (Triticum aestivum L.) in 1995 as reference crops for all three rotations. Two years of a grass-clover mixture in a five-year rotation showed positive effects with respect to most soil and plant parameters

    Countering Social Engineering through Social Media: An Enterprise Security Perspective

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    The increasing threat of social engineers targeting social media channels to advance their attack effectiveness on company data has seen many organizations introducing initiatives to better understand these vulnerabilities. This paper examines concerns of social engineering through social media within the enterprise and explores countermeasures undertaken to stem ensuing risk. Also included is an analysis of existing social media security policies and guidelines within the public and private sectors.Comment: Proceedings of The 7th International Conference on Computational Collective Intelligence Technologies and Applications (ICCCI 2015), LNAI, Springer, Vol. 9330, pp. 54-6

    A minimal model for spontaneous cell polarization and edge activity in oscillating, rotating and migrating cells

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    How the cells break symmetry and organize their edge activity to move directionally is a fun- damental question in cell biology. Physical models of cell motility commonly rely on gradients of regulatory factors and/or feedback from the motion itself to describe polarization of edge activity. Theses approaches, however, fail to explain cell behavior prior to the onset of polarization. Our analysis using the model system of polarizing and moving fish epidermal keratocytes suggests a novel and simple principle of self-organization of cell activity in which local cell-edge dynamics depends on the distance from the cell center, but not on the orientation with respect to the front-back axis. We validate this principle with a stochastic model that faithfully reproduces a range of cell-migration behaviors. Our findings indicate that spontaneous polarization, persistent motion, and cell shape are emergent properties of the local cell-edge dynamics controlled by the distance from the cell center.Comment: 8 pages, 5 figure
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