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41.
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Proper quadrat and sample sizes for sampling species frequency vary among vegetation types. This study found 10 × 10-cm quadrats most appropriate for frequency sampling dry mountain meadows when using a single quadrat size. If large, broad-leaved forbs are of special interest, 25 × 25-cm, 25 × 50-cm, or 50 × 50-cm quadrats may be useful. One hundred 10 × 10-cm quadrats adequately sampled most common species at alpha = 0.20 ± 10% frequency. In contrast, more than five hundred 0.29-m 2 circular plots usually were needed to sample individual species yield at alpha = 0.20 ± 20% of the mean. 相似文献
43.
Thomas Söderqvist Adam Bencard Camilla Mordhorst 《Studies in history and philosophy of science》2009,40(4):431-438
The acquisition and display of material artefacts is the raison d’être of museums. But what constitutes a museum artefact? Contemporary medicine (biomedicine) is increasingly producing artefacts that do not fit the traditional museological understanding of what constitutes a material, tangible artefact. Museums today are therefore caught in a paradox. On the one hand, medical science and technologies are having an increasing pervasive impact on the way contemporary life is lived and understood and is therefore a central part of the contemporary world. On the other hand, the objects involved in medical diagnostics and therapies are becoming increasingly invisible and intangible and therefore seem to have no role to play as artefacts in a museum context. Consequently, museums are at risk of becoming alienated from an increasingly important part of contemporary society. This essay elaborates the paradox by employing Gumbrecht’s (2004) distinction between ‘presence’ and ‘meaning’. 相似文献
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Summary 3, 16-diacetoxy-5-pregnane-20-one and the analogue pregn-5-ene derivative have been converted into (22R, 25R)-22, 26-imino-5-cholestane-3, 16-diol. The configuration at C-22 and C-25 was determined by transformation into the known (22R, 25R)-5-solanidane-3-one. Application of the Ruschig method led to (25R)-22,26-imino-5-cholest-22(N)-ene-3, 16-diol.
Solanum-Alkaloide. XVI. Mitteilung. — XV. Mitteilung:K. Schreiber undH. Ripperger, Tetrahedron Letters Nr.27, 9 (1960). 相似文献
Solanum-Alkaloide. XVI. Mitteilung. — XV. Mitteilung:K. Schreiber undH. Ripperger, Tetrahedron Letters Nr.27, 9 (1960). 相似文献
46.
Reaction of gold with collagen in vivo 总被引:1,自引:0,他引:1
47.
Iodine-131 in human thyroids in Britain following Chernobyl 总被引:1,自引:0,他引:1
48.
Stefansson H Helgason A Thorleifsson G Steinthorsdottir V Masson G Barnard J Baker A Jonasdottir A Ingason A Gudnadottir VG Desnica N Hicks A Gylfason A Gudbjartsson DF Jonsdottir GM Sainz J Agnarsson K Birgisdottir B Ghosh S Olafsdottir A Cazier JB Kristjansson K Frigge ML Thorgeirsson TE Gulcher JR Kong A Stefansson K 《Nature genetics》2005,37(2):129-137
A refined physical map of chromosome 17q21.31 uncovered a 900-kb inversion polymorphism. Chromosomes with the inverted segment in different orientations represent two distinct lineages, H1 and H2, that have diverged for as much as 3 million years and show no evidence of having recombined. The H2 lineage is rare in Africans, almost absent in East Asians but found at a frequency of 20% in Europeans, in whom the haplotype structure is indicative of a history of positive selection. Here we show that the H2 lineage is undergoing positive selection in the Icelandic population, such that carrier females have more children and have higher recombination rates than noncarriers. 相似文献
49.
Identification of a cluster of X-linked imprinted genes in mice 总被引:5,自引:0,他引:5
50.
Identifying the genetic variation underlying quantitative trait loci remains problematic. Consequently, our molecular understanding of genetically complex, quantitative traits is limited. To address this issue directly, we mapped three quantitative trait loci that control yeast sporulation efficiency to single-nucleotide resolution in a noncoding regulatory region (RME1) and to two missense mutations (TAO3 and MKT1). For each quantitative trait locus, the responsible polymorphism is rare among a diverse set of 13 yeast strains, suggestive of genetic heterogeneity in the control of yeast sporulation. Additionally, under optimal conditions, we reconstituted approximately 92% of the sporulation efficiency difference between the two genetically distinct parents by engineering three nucleotide changes in the appropriate yeast genome. Our results provide the highest resolution to date of the molecular basis of a quantitative trait, showing that the interaction of a few genetic variants can have a profound phenotypic effect. 相似文献