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951.
Helmut Kroll 《Vegetation History and Archaeobotany》2000,9(1):31-68
Publications on archaeological remains of cultivated plants have been collected, mainly from 1998, with some earlier ones, and some from 1999, A list is given of the finds according to taxon, country, site, and age 相似文献
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Helmut Sick 《Journal of Ornithology》1981,122(4):437-438
Ohne Zusammenfassung 相似文献
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Gerhard Stehlik Josef Kainzbauer Helmut Tausch Otto Richter 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,232(2):295-303
ExtrelutR extraction and glass capillary gas chromatography were applied to the routine determination of nicotine and its metabolites cotinine, nicotine-1′-N-oxide and cotinine-1-N-oxide in urine and plasma. After extraction of nicotine and cotinine both N-oxides and phendimetrazine-N-oxide (used as internal standard) were reduced to their bases by SO2 on-column and eluted by a mixture of diethyl ether and dichloromethane. The minimum detectable concentrations are 0.03 μg/ml for urinary nicotine and cotinine and 0.1 μg/ml for the N-oxides. In plasma samples the corresponding values are 5 ng/ml and 15 ng/ml, respectively, with sample values as small as 2 ml. The advantage of the direct determination of all four compounds of interest in one sample reduced the amount of plasma required. The straightforward and rapid extraction and reduction procedure as well as the long-term stability of the gas chromatographic separation system make the method suitable for routine application. 相似文献
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Although fluency theory predominates psychological research on human aesthetics, its most severe limitation may be to explain why art that challenges or even violates easy processing can nevertheless be aesthetically rewarding. We discuss long-standing notions on art’s potential to offer mental growth opportunities and to tap into a basic epistemic predisposition that hint at a fluency counteracting aesthetic pleasure mechanism. Based on divergent strands of literature on empirical, evolutionary, and philosophical aesthetics, as well as research on disfluency, we presumed that challenging art requires deliberate reflexive processing at the level of “aboutness” in order to be experientially pleasing. Here, we probed such a cognitive mastering mechanism, achieved by iterative cycles of elaboration, as predicted by our model of aesthetic experiences. For the study, two kinds of portraits were applied, one associable to a high fluency and one to a high stimulation potential (according to results of an extensive rating study). In Experiment 1, we provided a repeated evaluation task, which revealed a distinctive preference effect for challenging portraits that was absent in the visual exposition conditions of a familiarity and a mere exposure task (Experiment 2). In a follow-up task (Experiment 3) this preference effect was observed with a novel and more encompassing pool of portraits, which corroborated its stability and robustness. In an explorative stimulus-transfer task (Experiment 4), we investigated the presumed underlying mechanism by testing whether the observed effect would generalize onto novel portraits of the same artist-specific styles. Results discounted an alternative interpretation of a perceptual adaptation effect and hinted at meaning-driven mental activity. Conjointly, findings for inexperienced viewers were indicative of an elaboration based mastering mechanism that selectively operated for mentally challenging portraits. Moreover, findings were in line with a dual-process view of human preference formation with art. Theoretical implications and boundary conditions are discussed. 相似文献
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Biodiversity effects on ecosystem functioning: emerging issues and their experimental test in aquatic environments 总被引:13,自引:0,他引:13
Paul S. Giller Helmut Hillebrand Ulrike-G. Berninger Mark O. Gessner Stephen Hawkins Pablo Inchausti Cheryl Inglis Heather Leslie Björn Malmqvist Michael T. Monaghan Peter J. Morin Gregory O'Mullan 《Oikos》2004,104(3):423-436
Recent experiments, mainly in terrestrial environments, have provided evidence of the functional importance of biodiversity to ecosystem processes and properties. Compared to terrestrial systems, aquatic ecosystems are characterised by greater propagule and material exchange, often steeper physical and chemical gradients, more rapid biological processes and, in marine systems, higher metazoan phylogenetic diversity. These characteristics limit the potential to transfer conclusions derived from terrestrial experiments to aquatic ecosystems whilst at the same time provide opportunities for testing the general validity of hypotheses about effects of biodiversity on ecosystem functioning. Here, we focus on a number of unique features of aquatic experimental systems, propose an expansion to the scope of diversity facets to be considered when assessing the functional consequences of changes in biodiversity and outline a hierarchical classification scheme of ecosystem functions and their corresponding response variables. We then briefly highlight some recent controversial and newly emerging issues relating to biodiversity‐ecosystem functioning relationships. Based on lessons learnt from previous experimental and theoretical work, we finally present four novel experimental designs to address largely unresolved questions about biodiversity‐ecosystem functioning relationships. These include (1) investigating the effects of non‐random species loss through the manipulation of the order and magnitude of such loss using dilution experiments; (2) combining factorial manipulation of diversity in interconnected habitat patches to test the additivity of ecosystem functioning between habitats; (3) disentangling the impact of local processes from the effect of ecosystem openness via factorial manipulation of the rate of recruitment and biodiversity within patches and within an available propagule pool; and (4) addressing how non‐random species extinction following sequential exposure to different stressors may affect ecosystem functioning. Implementing these kinds of experimental designs in a variety of systems will, we believe, shift the focus of investigations from a species richness‐centred approach to a broader consideration of the multifarious aspects of biodiversity that may well be critical to understanding effects of biodiversity changes on overall ecosystem functioning and to identifying some of the potential underlying mechanisms involved. 相似文献
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