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The concentrations of two major elements and thirteen trace elements in 73 selected sherds of fine grey ware from the Iron Age and Roman period, excavated at Conimbriga, Santa Olaia and Tavarede, Portugal, were determined by instrumental neutron activation analysis. These concentrations were used to calculate distance matrices which were then subjected to cluster analysis employing SAHN and k-means methods, as well as to principal components analysis, to group the sherds according to the overall similarity of their compositional characteristics. The results showed that equivalent groupings appeared regardless of the taxonomic method used. Two major clusters were recognized corresponding to two different sites, namely Conimbriga and Santa Olaia, suggesting that the ceramics from these sites were made locally. No significant differences in compositional patterns were observed between iron age and roman sherds from Conimbriga.  相似文献   
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This study explores the spatial structure of retailing in Milwaukee, Wisconsin, in the era before the introduction of the electric streetcar in 1890. It uses city directory listings to chart changes in the numbers and types of retail outlets, their degree of nucleation and the functional complexity of such nucleations. The evidence suggests the early appearance of non-central retailing, the rapid dispersal of high as well as low order goods to non-central sites and the early emergence initially of a three-level and then, by 1870, a four-level hierarchy of shopping clusters. The pattern of retail clustering varied with the class and ethnic character of neighbourhoods, and clusters gravitated toward major arterial routes even in the pre-mass transit ear. Urban retailing in the second half of the nineteenth century was neither randomly dispersed nor over-whelmingly concentrated in a single central retail district, but developed a spatial hierarchy that clearly anticipated modern patterns.  相似文献   
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A problem which has arisen in discussions of an elm-disease explanation for the Neolithic elm decline has been the lack of fossil records of Scolytus scolytus (F.) (elm bark beetle), which is the main carrier of the fungus which causes the present epidemic of Dutch Elm Disease. Now, the discovery of wing cases of two individuals from elm decline deposits at Hampstead Heath, London, proves that the beetle was present in Britain during this episode. The deposits in which it occurs are described, and the various implications for elm disease causing, aiding or at least occurring during this stage of the early Neolithic are discussed.  相似文献   
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