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Surface oscillations — A possible source of fracture induced electromagnetic radiation 总被引：1，自引：0，他引：1
Radio frequency electromagnetic radiation (EMR) registered hundreds of kilometres away from an earthquake epicentre is detected hours before earthquakes. Yet, accurate earthquakes prediction by their self-induced EMR still remains in its infancy due in part to the lack of understanding of EMR's origin. Here we present a viable model of this origin, according to which EMR is emitted by an oscillating dipole created by ions moving collectively as a surface wave on both sides of the crack; when the crack halts, the EMR pulse amplitude decays by interaction with bulk phonons. The model is shown to be able to provide crack dimensions and velocities, to explain some general similarities of different fracturing processes and indicate the existence of a general failure mechanism. Results raise the hope of developing an EMR based genuine earthquake prediction system. 相似文献
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Sedimentary marine systems are often highly productive and perform important nutrient regeneration functions as they efficiently decompose organic material. In recent years the role of habitat effects and of species composition in ecosystem functioning has become of interest. Estuarine environments are frequently subject to considerable anthropogenic pressures whilst supporting a variety of habitats ranging from well sorted soft muds through biogenically stable sediments to highly mobile coarse sands. There is therefore considerable spatial complexity in habitat type and faunal composition. This study set out to observe the effects of altering the topographical habitat features of an estuarine mudflat on a range of porewater nutrient concentrations (NH4 + , NO3 − , NO2 − , PO4 3− and SiO) collected from four depths (3, 5, 9, and 12 cm) and on faunal composition. Two treatments (Shelled Nets and Net Controls) were used to alter the topography from simple mud to a mussel shell crumble and were compared to un-manipulated Control areas. Sediment granulometry and organic matter content analyses alongside biological traits analysis of the fauna were also conducted.
Differences were observed in porewater nutrient concentrations between the Control and both netted treatments at 5 cm depth only; the species diversity and abundance were also different in the netted treatments compared to the Controls, although no difference between the two manipulated treatments were observed. The changes in faunal composition were attributed solely to the altered topography and the observed nutrient changes were attributed to the faunal alteration rather than the topographical manipulation. 相似文献
Differences were observed in porewater nutrient concentrations between the Control and both netted treatments at 5 cm depth only; the species diversity and abundance were also different in the netted treatments compared to the Controls, although no difference between the two manipulated treatments were observed. The changes in faunal composition were attributed solely to the altered topography and the observed nutrient changes were attributed to the faunal alteration rather than the topographical manipulation. 相似文献
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Vladimir Frid Gady Liskevich Dmitriy Doudkinski Nikolay Korostishevsky 《Environmental Geology》2008,53(7):1503-1508
This paper deals with an employment of electrical resistivity imaging (ERI) for survey of leachate content on the waste disposal
site in Northern Israel. The research consisted of conducting ten ERI lines and drilling investigation wells. Data simulation
used a 2D EarthImager inversion program. Analysis of 2D ERI interpretation results shows that determination of the boundary
between the landfill body bottom intensively saturated with leachates and underlying layers of highly water saturated fat
nonconsolidated clays presents a challenge. However, statistical analysis of ERI data indicates that standard deviation and
confidence interval of a set of resistivity data measured in the landfill body are significantly larger than those in underlying
clays. Moreover, maximum changes of these parameters are found on the boundary between landfill body and underlying soil,
thus reflecting natural differences in scattering of resistivity data measured in these two objects. 相似文献
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Frid C. L. J; Harwood K. G.; Hall S. J.; Hall J. A. 《ICES Journal of Marine Science》2000,57(5):1303-1309
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Implementing ecosystem-based management requires methods of assessing the quality of habitats to deliver the high-level objective of achieving healthy ecosystems. ‘Habitat’ has been interpreted in different ways and this has confused the debate over which attributes constitute ‘quality’. Three definitions of quality for habitats are advanced: ‘species’, ‘reference’ and ‘functional’ . Operational measures associated with these are evaluated in terms of their utility to deliver policy objectives. It is concluded that functional definitions/measures of quality are most appropriate to deliver ecosystem-based management although measures of species and reference quality may support assessment of the functional quality of habitats. 相似文献
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Ecosystem-based management of fisheries: is science limiting? 总被引：4，自引：0，他引：4
Frid Chris L.J.; Paramor Odette A.L.; Scott Catherine L. 《ICES Journal of Marine Science》2006,63(9):1567-1572