447 resultados para Gastrointestinaler Krebs
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This layer is a georeferenced raster image of the historic paper map entitled: Map of Cincinnati and vicinity : compiled for Williams' Cincinnati directory, by E.F. Layman, civil engineer; engraved by the Henderson-Achert-Krebs Lithographing Co. It was published by Williams & Co. in 1893. Scale [ca. 1:15,000]. Covers also parts of Kentucky below the Ohio River.The image inside the map neatline is georeferenced to the surface of the earth and fit to the Ohio South State Plane NAD 1983 coordinate system (in Feet) (Fipszone 3402). All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as roads, railroads and stations, selected buildings, city ward boundaries, drainage, parks, cemeteries, and more. Includes index.This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection. These maps typically portray both natural and manmade features. The selection represents a range of originators, ground condition dates, scales, and map purposes.
Quaternary refugia of the sweet chestnut (Castanea sativa Mill.): an extended palynological approach
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Knowledge about the glacial refugia of the thermophilous European Castanea sativa Mill. (sweet chestnut) is still inadequate. Its original range of distribution has been masked by strong human impact. Moreover, under natural conditions the species was probably admixed with other taxa (such as Quercus, Fraxinus, Fagus, Tilia) and thus possibly represented by low percentages in pollen records. In this paper we try to overcome the difficulties related to the scarcity and irregularity of chestnut pollen records by considering 1471 sites and extending the palynological approach to develop a Castanea refugium probability index (IRP), aimed at detecting possible chestnut refugia where chestnuts survived during the last glaciation. The results are in close agreement with the current literature on the refugia of other thermophilous European trees. The few divergences are most probably due to the large amount of new data integrated in this study, rather than to fundamental disagreements about data and data interpretation. The main chestnut refugia are located in the Transcaucasian region, north-western Anatolia, the hinterland of the Tyrrhenian coast from Liguria to Lazio along the Apennine range, the region around Lago di Monticchio (Monte Vulture) in southern Italy, and the Cantabrian coast on the Iberian peninsula. Despite the high likelihood of Castanea refugia in the Balkan Peninsula and north-eastern Italy (Colli Euganei, Monti Berici, Emilia-Romagna) as suggested by the IRP, additional palaeobotanical investigations are needed to assess whether these regions effectively sheltered chestnut during the last glaciation. Other regions, such as the Isère Département in France, the region across north-west Portugal and Galicia, and the hilly region along the Mediterranean coast of Syria and Lebanon were classified as areas of medium refugium probability. Our results reveal an unexpected spatial richness of potential Castanea refugia. It is likely that other European trees had similar distribution ranges during the last glaciation. It is thus conceivable that shelter zones with favourable microclimates were probably more numerous and more widely dispersed across Europe than so far assumed. In the future, more attention should be paid to pollen traces of sporadic taxa thought to have disappeared from a given area during the last glacial and post-glacial period.
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The history of Castanea sativa (sweet chestnut) cultivation since medieval times has been well described on the basis of the very rich documentation available. Far fewer attempts have been made to give a historical synthesis of the events that led to the cultivation of sweet chestnut in much earlier times. In this article we attempt to reconstruct this part of the European history of chestnut cultivation and its early diffusion by use of different sources of information, such as pollen studies, archaeology, history and literature. Using this multidisciplinary approach, we have tried to identify the roles of the Greek and Roman civilizations in the dissemination of chestnut cultivation on a European scale. In particular, we show that use of the chestnut for food was not the primary driving force behind the introduction of the tree into Europe by the Romans. Apart from the Insubrian Region in the north of the Italian peninsula, no other centre of chestnut cultivation existed in Europe during the Roman period. The Romans may have introduced the idea of systematically cultivating and using chestnut. In certain cases they introduced the species itself; however no evidence of systematic planting of chestnut exists. The greatest interest in the management of chestnut for fruit production most probably developed after the Roman period and can be associated with the socio-economic structures of medieval times. It was then that self-sufficient cultures based on the cultivation of chestnut as a source of subsistence were formed.
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Determining the manner in which food webs will respond to environmental changes is difficult because the relative importance of top-down vs. bottom-up forces in controlling ecosystems is still debated. This is especially true in the Arctic tundra where, despite relatively simple food webs, it is still unclear which forces dominate in this ecosystem. Our primary goal was to assess the extent to which a tundra food web was dominated by plant-herbivore or predator--rey interactions. Based on a 17-year (1993-2009) study of terrestrial wildlife on Bylot Island, Nunavut, Canada, we developed trophic mass balance models to address this question. Snow Geese were the dominant herbivores in this ecosystem, followed by two sympatric lemming species (brown and collared lemmings). Arctic foxes, weasels, and several species of birds of prey were the dominant predators. Results of our trophic models encompassing 19 functional groups showed that <10% of the annual primary production was consumed by herbivores in most years despite the presence of a large Snow Goose colony, but that 20-100% of the annual herbivore production was consumed by predators. The impact of herbivores on vegetation has also weakened over time, probably due to an increase in primary production. The impact of predators was highest on lemmings, intermediate on passerines, and lowest on geese and shorebirds, but it varied with lemming abundance. Predation of collared lemmings exceeded production in most years and may explain why this species remained at low density. In contrast, the predation rate on brown lemmings varied with prey density and may have contributed to the high-amplitude, periodic fluctuations in the abundance of this species. Our analysis provided little evidence that herbivores are limited by primary production on Bylot Island. In contrast, we measured strong predator-prey interactions, which supports the hypothesis that this food web is primarily controlled by top-down forces. The presence of allochthonous resources subsidizing top predators and the absence of large herbivores may partly explain the predominant role of predation in this low-productivity ecosystem.
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Bibliographical references included in "Note" [p.32]
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Mode of access: Internet.
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Lebenslauf.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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Michaelis Ettmülleri ... De virtute opii diaphoretica dissertatio, 48 p.