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Melanism: Evolution in Action by Michael E.N. Majerus Oxford University Press, 1998. £55.00/$105.00 hbk, £23.95/$45.00 pbk (xiii+352 pages) ISBN 0 19 854983 0 / 0 19 854 982 2.  相似文献   

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Studies show that black pepper can be propagated rapidly by leaf cuttings, the results far exceeding those obtained by conventional methods. An innovation in the use of leaf cuttings is also described in this study.  相似文献   

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The stick insect Peruphasma schultei stands out from other insects by its deep matt black cuticle. We tested whether the appearance of P. schultei is due to microstructures of the cuticle, a phenomenon that has recently been described for the velvet black scales of the Gaboon viper. The shiny black stick insect Anisomorpha paromalus served as a control. We found that the P. schultei cuticle is characterised by two different types of microstructures, tall elevations with a maximum size of 18 μm and small structures with a height of 4 μm. Other than in the snake, P. schultei microstructures do not bear nanostructures. The microstructures scatter light independently of the viewing angle. This causes the matt appearance of the cuticle, whereas pigments are responsible for the black colouration, resulting in a maximum reflectance of 2.8% percent. The microstructures also cause the hydrophobic properties of the cuticle with contact angles near 130°. Resin replicas and bleaching of the cuticle strongly support these results. Moreover, the matt black cuticle has a higher heat absorption compared to the control. We discuss the selective benefit of the matt black appearance of P. schultei in the context of behaviour, ecology and phylogeny.  相似文献   

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This article examines how the US military uses race inequalities to mobilize black single mothers for enlistment of their children in the Armed Forces. Through an analysis of military recruitment materials during the height of the US War on Terrorism, I demonstrate how the military disproportionately shows black single mothers going through a process of reacting to their child's enlistment (with fear and worry), welcoming the military institution as the co-parent, and accepting enlistment as a venue for education and career opportunities (productive citizenship). The military models a citizen-mother who supports their child's enlistment, while unquestionably supporting the war. This exploits the obligations of citizenship for black single mothers, whose citizenship is already under scrutiny. By targeting the children of these mothers for recruitment, the military encourages a higher burden of military participation on an already underprivileged segment of the population.  相似文献   

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Iu G Rovin 《Biofizika》1978,23(4):638-640
Effect of water-soluble detergents, such as triton X-100, saponin and trimethyl octadecylammonium bromide on the concentration of black spots, tension and stability of black lipid membranes was studied. Changes in mechanic stability of the lipid bilayer are discovered, which are in a good correlation with the litic effect of true detergents on cell membranes.  相似文献   

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An assay for beta-alanine transaminase activity in extracts of Drosophila melanogaster has been developed. By use of this assay, the levels of beta-alanine transaminase activity in several strains of flies has been examined as a function of developmental age. The black mutation shows elevated levels of activity compared to wild type, while suppressor of black strains show decreased levels compared to wild type.  相似文献   

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The elements present in the fungal structures produced by Piedraia hortae in vivo and in vitro have been investigated using electron microscopy X-ray microanalysis. Phosphorus, sulphur and calcium were detected in the nodules which developed on hair and on colonies on culture. These elements belong to the extracellular material that compacts the pseudoparenchymatous organization of the fungus. They may be present due to the capacity of melanin-like pigments to sequester ions and/or they may form part of the sulphates and phosphates of the polyanionic mucopolysaccharides that constitute the extracellular material. Environmental contaminants such as aluminium, silicon and iron were detected exclusively on the surface of the nodule. They were deposited or linked to the residual molecules produced during the breakdown of the cuticular keratin. The advantages of these techniques for elucidating the chemical nature of fungal structures are discussed.  相似文献   

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The structure of a tetrameric form of the spider neurotoxin, alpha-latrotoxin, has been determined by single particle cryo-electron microscopy. It reveals a pore complex with extended arms that could bind receptors involved in synaptic vesicle exocytosis.  相似文献   

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