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141.
E. Schnepi L. Jaenicke K. Krickeberg G. Schumann G. Höhler W. Bruch D. Jung K. J. Euler C. K. Jørgensen P. Zuman J. Goubeau H. Schmidbaur L. Horner W. P. Neumann W. A. Bingel T. Reichstein W. Sandritter C. H. Eugster R. Dietz G. Ohloff H. Markl M. Lindauer 《Die Naturwissenschaften》1970,57(4):200-204
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Surface waves and roughness in self-aerated supercritical flow 总被引:1,自引:1,他引:1
In high-velocity open channel flows, free-surface aeration is commonly observed. The effects of surface waves on the air–water
flow properties are tested herein. The study simulates the air–water flow past a fixed-location phase-detection probe by introducing
random fluctuations of the flow depth. The present model yields results that are close to experimental observations in terms
of void fraction, bubble count rate and bubble/droplet chord size distributions. The results show that the surface waves have
relatively little impact on the void fraction profiles, but that the bubble count rate profiles and the distributions of bubble
and chord sizes are affected by the presence of surface waves. 相似文献
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Robert M. Sanford Hubert B. Stroud 《Journal of Environmental Planning and Management》2000,43(5):623-641
Vermont's progressive land development and land use law (Act 250), now 30 years old, provides district and state control over major developments through the review of environmental and planning criteria. Although it is comprehensive in nature, the law is applied on a case-by-case basis, which can make the results inconsistent. Up to now, there have been no significant studies of the role of Act 250 in conserving water quality through stream buffers. This research uses four case-studies of stream buffer use along Vermont streams as a step toward understanding and improving the role of comprehensive land use regulation in protective buffers. Such a study, while directly applicable to Vermont, could be useful to other states that are interested in improving compliance with existing regulations or in adopting new land use legislation. 相似文献
150.
Keith W. Sockman Jack Weiss Michael S. Webster Vanessa Talbott Hubert Schwabl 《Behavioral ecology and sociobiology》2008,62(4):617-625
Maternally derived androgen hormones concentrate in avian egg yolks as the yolks grow on the female’s ovary, possibly forming
a basis for important maternal effects in birds. In the American kestrel (Falco sparverius), experimental elevation of yolk androgens in the first-laid egg of a clutch (a-egg) to the concentrations found naturally
in a clutch’s later-laid eggs reduces the growth rate of a-egg nestlings compared to controls. These findings, together with
discoveries from other species that the effects of yolk androgens on growth of female nestlings may differ from their effects
on growth of male nestlings, raise the hypothesis that natural changes in yolk-androgen concentrations with laying order are
ultimately due to a difference between the sexes in their yolk-androgen sensitivity and between early- and late-laid eggs
in their sex ratio. By re-analyzing previously published data and adding to the analysis data from previously unanalyzed blood
samples used for sex determination, we investigated possible sex-specific effects of yolk-androgens in the context of a potential
sex-biased laying order in free-living American kestrels. We used a multi-level, mixed model with a Gompertz function to analyze
growth of nestlings hatching from a-eggs that were control-treated or in which we experimentally elevated yolk-androgen concentrations
shortly after laying to the higher concentrations naturally found in later-laid eggs. We discovered that male nestlings were
more susceptible than female nestlings to growth inhibition by yolk-androgen elevation but did not find a bias in sex ratio
with respect to laying order. Together, these findings do not support the above hypothesis. However, they are consistent with
the hypothesis that sex differences in yolk-androgen sensitivity enable mothers to economically tune reproductive effort to
an individual offspring’s reproductive value, which can vary more for one sex than the other. 相似文献