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151.
152.
Hermann Fahlenbrach 《Die Naturwissenschaften》1935,23(18):288-288
153.
Summary. The plant apparency hypothesis predicts that apparent plants invest in broadly effective defences such as tannins while unapparent
plants invest in specific toxins such as alkaloids. The stress hypothesis states that plants invest in cheaper defences if
they have evolved in habitats that impose abiotic limitations to plant fitness. We tested these hypotheses by determining
the concentrations of alkaloids and tannins in a representative sample of the vascular plants of continental Chile (with exclusion
of Pteridophyta, Cactaceae, and Poaceae) consisting of 396 species. In a subsample of 166 species which contained both alkaloids
and tannins, we constructed the A/T index (A/T = [alkaloids]/ [tannins]). We discarded the presumed effect of phylogeny (as
estimated by taxonomy) on the variation observed in the data because no correlation of A/T with taxonomic relationships among
species either at family or genus levels was found in a nested ANOVA with genera nested in families. Concentration of alkaloids
was negatively correlated with that of tannins. We compared the value of A/T among species differing in life form (herbs,
shrubs or trees), herb longevity (annual or perennial), leaf-shedding manner of woody plants (deciduous or evergreen), latitudinal
range, and level of water stress typical in their natural habitat. Unapparent plants (herbs, annual) exhibited higher mean
A/T index than apparent plants (shrubs and trees, perennial). A/T did not correlate with latitudinal range. Mean A/T values
decreased from deserts to deciduous forests. The comparisons were not always significant due to the inevitable unbalance of
the data set which lowers the power of the statistical tests employed. The results suggest that chemical defences are indeed
distributed in a non-random manner among plants, and that to a large extent the predictions derived from the apparency and
stress hypotheses are sustained. 相似文献
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Chrysoula Gubili Ryan Johnson Enrico Gennari W. Hermann Oosthuizen Deon Kotze Mike Me?er David W. Sims Catherine S. Jones Leslie Robert Noble 《Marine Biology》2009,156(10):2199-2207
Visual identification of naturally acquired marks has been a popular if subjective method of animal identification and population
estimation over the last 40 years. Molecular genetics has also independently developed objective individual marking techniques
during the same period. Here, we assess the concordance of individual great white shark (Carcharodon carharias) dorsal fin recognition and identification, using seven microsatellite loci as the independent unbiased arbiter, over a period
of 5 years. As a monitoring technique, fin photographs offer a very good individual identification key for white sharks over
a relatively short period of time (5 years), matching with genetic data in about 85% of cases, whilst caution and a continuously
updated database is required for animal recognition over a longer period. 相似文献
160.
AbstractObjective: Particular testing by functional decomposition of the automated driving function can potentially contribute to reducing the effort of validating highly automated driving functions. In this study, the required size of test suites for scenario-based testing and the potential to reduce it by functional decomposition are quantified for the first time.Methods: The required size of test suites for scenario-based approval of a so-called Autobahn-Chauffeur (SAE Level 3) is analyzed for an exemplary set of scenarios. Based on studies of data from failure analyses in other domains, the possible range for the required test coverage is narrowed down and suitable discretization steps, as well as ranges for the influence parameters, are assumed. Based on those assumptions, the size of the test suites for testing the complete system is quantified. The effects that lead to a reduction in the parameter space for particular testing of the decomposed driving function are analyzed and the potential to reduce the validation effort is estimated by comparing the resulting test suite sizes for both methods.Results: The combination of all effects leads to a reduction in the test suites’ size by a factor between 20 and 130, depending on the required test coverage. This means that the size of the required test suite can be reduced by 95–99% by particular testing compared to scenario-based testing of the complete system.Conclusions: The reduction potential is a valuable contribution to overcome the parameter space explosion during the validation of highly automated driving. However, this study is based on assumptions and only a small set of exemplary scenarios. Thus, the findings have to be validated in further studies. 相似文献