1,876 research outputs found

    The investigation of a lowland peat bog in County Durham

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    Palaeobiology, ecology, and distribution of stromatoporoid faunas in biostromes of the mid-Ludlow of Gotland

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    Six well exposed mid−Ludlow stromatoporoid−dominated reef biostromes in four localities from the Hemse Group in southeastern Gotland, Sweden comprise a stromatoporoid assemblage dominated by four species; Clathrodictyon mohicanum, “Stromatopora” bekkeri, Plectostroma scaniense, and Lophiostroma schmidtii. All biostromes investigated in this area (of approximately 30 km2) are interpreted to belong to a single faunal assemblage forming a dense accumulation of fossils that is probably the best exposed stromatoporoid−rich deposit of the Silurian. The results from this comprehensive study strengthen earlier interpretations of a combination of genetic and environmental control on growth−forms of the stromatoporoids. Growth styles are similar for stromatoporoids in all six biostromes. Differences in biostrome fabric are due to variations in the degree of disturbance by storms. The uniformity of facies and the widespread low−diversity fauna support the view that palaeoenvironmental conditions were similar across the area where these biostromes crop out, and promoted the extraordinary growth of stromatoporoids in this shallow shelf area

    An iron(ii) spin-crossover metallacycle from a back-to-back bis-[dipyrazolylpyridine]

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    The syntheses of 4-mercapto-2,6-di(pyrazol-1-yl)pyridine (bppSH) and bis[2,6-di(pyrazol-1-yl)pyrid-4-yl]disulfide (bppSSbpp) are reported. In contrast to previously published “back-to-back” bis-[2,6-di(pyrazol-1-yl)pyridine] derivatives, which form coordination polymers with transition ions that are usually insoluble, bppSSbpp yields soluble oligomeric complexes with iron(II) and zinc(II). Mass spectrometry and DOSY data show that [{Fe(μ-bppSSbpp)}n]2n+ and [{Zn(μ-bppSSbpp)}n]2n+ form tetranuclear metallacycles in nitromethane solution (n = 4), although 1H NMR and conductivity measurements imply the iron compound may undergo more fragmentation than its zinc congener. Both [{Fe(bppSH)2]2+ and [{Fe(μ-bppSSbpp)}n]2n+ exhibit thermal spin-crossover in CD3NO2 solution, with midpoint temperatures near 245 K. The similarity of these equilibria implies there is little cooperativity between the iron centres in the metallacyclic structures

    Pollen transport and deposition in riverine and marine environments within the humid tropics of northeastern Australia

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    Mechanisms of pollen transport in the humid tropics region of northeastern Australia were investigated to support the interpretation of a long Quaternary pollen record from ODP Site 820 located on the adjacent continental slope. Pollen analysis of surface sediment samples from the channels of two major river catchments demonstrated internal consistency in pollen spectra and little fluvial pollen sorting in relation to sediment variation. Differences in modem pollen spectra between catchments reflect existing variation in vegetation cover that, in turn, reflects climatic differences between catchments. Recent pollen spectra from top samples of the ODP core have sufficient in common with the riverine samples to suggest that the rivers are contributing a major pollen component to the offshore sediments, but these have been size sorted by marine action. Recent pollen samples from core tops taken from the Grafton Passage on the continental shelf that was thought to be the major passage for pollen transport to ODP Site 820 show significant differences to both riverine and ODP samples and suggest that pollen are dispersed across the continental shelf and through the outer Great Barrier Reef system in a more complex way than anticipated. (c) 2004 Elsevier B.V. All rights reserved

    Palaeobiogeography of the Quaternary of Australasia

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    Performing heritage: the use of live 'actors' in heritage presentations

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    This paper investigates the phenomenon of 'living history' presentations of heritage, using live 'actors' to portray historical characters. Its aim is to discuss these presentations in the context of what may be understood as 'heritage', and of the nature of 'performance'. Four case studies of heritage sites, each important as a tourist attraction, have been selected for detailed study, together with a number of other examples of heritage performance. It is clear from the empirical work that different performance strategies are employed within the heritage industry and by individual 'actors'. Most of the performers take part as a leisure activity, and many do not consider themselves to be 'performing' at all. The greatest concern of participants lies in the degree of authenticity of the performance. Through 'living history', the 'actors' are drawn into an experience of heritage which has real meaning for them, and which may contribute both to a sense of identity and to an enhanced understanding of society, past and present. The popularity of such presentations with visitors also indicates that similar benefits are perceived by the 'audience'

    Evaporating waterbody effects in a simplified urban neighbourhood: A RANS analysis

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    The incorporation of nature-based solutions comprising green and blue infrastructure is often touted as a way to cool cities and enhance pollutant removal. However, there is little agreement between different methodologies to measure the effect of any single intervention. Here, we present 3D steady RANS simulations to investigate the influence of waterbody on in-canyon flow structure, temperature (T*) and water vapour (!*) distribution in a simplified urban neighbourhood. A novel solver that captures evaporation effects is developed and validated against wind tunnel experiments. Simulations are performed under neutral atmospheric conditions for forced -and mixed-convection cases and different air-water temperature differences, indicative of either daytime or night-time conditions. Results under forced convection show minimal impact on the flow structure, whilst T* and !* effects are distributed primarily over and around the water surface. However, the mixed-convection case shows that a cooler waterbody weakens the principal vortex in the open square, whilst T* and !* effects reach further upwind and are more widely distributed in the spanwise direction. A warmer waterbody is shown to disrupt the skimming flow structure, indicating a possible heat and pollutant removal mechanism from around the waterbody and also downwind canyons
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