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131.
The problems of interpretation of many overlapping species lists of fossil assemblages are discussed using the example of insect faunas from a late medieval farm site in southern Iceland. Numerical techniques were employed, principally those available within the CLUSTAN package, and it was concluded that a considerable refinement in interpretation was achieved. Such quantitative procedures are suitable for groups other than fossil insects but their employment cannot be regarded as a substitute for, rather than an adjunct to, a sound ecological approach. 相似文献
132.
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
133.
G. P. King 《Australian Journal of International Affairs》1960,14(3):306-317
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James M. McCormick 《The American review of Canadian studies》2016,46(4):474-495
Both Canada and the United States have “pivoted” toward Asia in their foreign policy over the past decade, although emphases in those pivots differed between the two countries. The former focuses on an economic pivot initially, the latter on a security one. What factors explain these shifts? What was the magnitude of policy change by both? Utilizing some important theoretical works by Charles Hermann, we discuss the factors that appear to have brought about this policy change toward Asia, outline the actions and activities that both countries have initiated toward Asia in the past decade to illustrate the type and magnitude of policy change that has occurred, and compare some areas of political, economic, and military similarities between Canada and the United States toward this region. Finally, we assess the likely future of these pivots to Asia in light of the change in political leadership within both nations. 相似文献
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María José Pérez González 《Romance Quarterly》2016,63(1):4-13
ABSTRACTTeresa de Jesús (1515–1582) lives in a patriarchal society opposed to the intellectual and spiritual development of women, something that she will not only not accept but also fight against, claiming a series of rights (the right to life, to expression, to autonomy, to the free development of her abilities, to have an active role in the Church, to relate to God through prayer, etc.) in spite of the restrictions of censorship and the cloud of suspicion that hung over her for being a mystic, the founder of convents, and the daughter and granddaughter of a converso. Furthermore, Teresa, with her reforms, would present an alternative life for women, as her convents would be spaces for freedom and women's solidarity. 相似文献
139.
Mineral precipitation in an open fracture plays a crucial role in the evolution of fracture permeability in rocks, and the microstructural development and precipitation rates are closely linked to fluid composition, the kind of host rock as well as temperature and pressure. In this study, we develop a continuum thermodynamic model to understand polycrystalline growth of quartz aggregates from the rock surface. The adapted multiphase‐field model takes into consideration both the absolute growth rate as a function of the driving force of the reaction (free energy differences between solid and liquid phases), and the equilibrium crystal shape (Wulff shape). In addition, we realize the anisotropic shape of the quartz crystal by introducing relative growth rates of the facets. The missing parameters of the model, including surface energy and relative growth rates, are determined by detailed analysis of the crystal shapes and crystallographic orientation of polycrystalline quartz aggregates in veins synthesized in previous hydrothermal experiments. The growth simulations were carried out for a single crystal and for grain aggregates from a rock surface. The single crystal simulation reveals the importance of crystal facetting on the growth rate; for example, growth velocity in the c‐axis direction drops by a factor of ~9 when the faceting is complete. The textures produced by the polycrystal simulations are similar to those observed in the hydrothermal experiments, including the number of surviving grains and crystallographic preferred orientations as a function of the distance from the rock wall. Our model and the methods to define its parameters provide a basis for further investigation of fracture sealing under varying conditions. 相似文献
140.
Pore pressure and fluid flow during the deformational history of geologic structures are directly influenced by tectonic deformation events. In this contribution, 2D plane strain finite element analysis is used to study the influence of different permeability distributions on the pore pressure field and associated flow regimes during the evolution of visco‐elastic single‐layer buckle folds. The buckling‐induced fluid flow regimes indicate that flow directions and, to a lesser degree, their magnitudes vary significantly throughout the deformation and as a function of the stratigraphic permeability distribution. The modelling results suggest that the volumetric strain and the permeability distribution significantly affect the resulting flow regime at different stages of fold development. For homogeneous permeability models (k > 10?21 m2), low strain results in a mostly pervasive fluid flow regime and is in agreement with previous studies. For larger strain conditions, fluid focusing occurs in the buckling layer towards the top of the fold hinge. For low permeabilities (<10?21 m2), local focused flow regimes inside the buckling layer emerge throughout the deformation history. For models featuring a low‐permeability layer embedded in a high‐permeability matrix or sandwiched between high‐permeability layers, focused flow regimes inside the folded layer result throughout the deformation history, but with significant differences in the flow vectors of the surrounding layers. Fluid flow vectors induced by the fold can result in different, even reversed, directions depending on the amount of strain. In summary, fluid flow regimes during single‐layer buckling can change from pervasive to focused and fluid flow vectors can be opposite at different strain levels, that is the flow vectors change significantly through time. Thus, a complete understanding of fluid flow regimes associated with single‐layer buckle folds requires consideration of the complete deformation history of the fold. 相似文献