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41.
Oriental orchid (Cymbidium pumilum) attracts drones of the Japanese honeybee (Apis cerana japonica) as pollinators. 总被引:2,自引:0,他引:2
The discovery that drones of the Japanese honeybee (Apis cerana japonica) pollinate the oriental orchid (Cymbidium pumilum) is reported. Drones are attracted to the orchid flower aroma mainly during their mating flights in April through May. Some drones cluster on the flower racemes and others insert their heads deep into the flowers. Drones with pollinia on their scutellum visit other orchids, which facilitates pollination. Individual workers and swarming colonies are also strongly attracted by the flower aroma, but the allopatric western honeybee (Apis mellifera) is not attracted. 相似文献
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Stearoyl CoA desaturase activity in liver microsomes, and insulin, thyroxine, and triiodothyronine levels in serum were measured after administration of streptozocin (STZ) and its antagonists to rats. The effect of STZ, which caused hyperglycemia and inhibited the desaturase activity, was antagonized by 2-desoxyglucose and 3-O-methyl-glucose; 1-O-methyl-3-desoxyglucose and 1-O-methyl-3-O-methylglucose were without any effect. The enzyme activity plotted against insulin levels showed a broad sigmoidal curve, whereas the activities versus thyroid hormone levels showed steeper sigmoidal curves. 相似文献
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The present study discusses the relationships between two independently developed models of games with incomplete information,hypergames(Bennett,1977) and Bayesian games(Harsanyi, 1967).The authors first show that any hypergame can naturally be reformulated in terms of Bayesian games in an unified way.The transformation procedure is called Bayesian representation of hypergame. The authors then prove that some equilibrium concepts defined for hypergames are in a sense equivalent to those for Bayesian games.Furthermore,the authors discuss carefully based on the proposed analysis how each model should be used according to the analyzer’s purpose. 相似文献
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Green revolution: a mutant gibberellin-synthesis gene in rice 总被引:36,自引:0,他引:36
Sasaki A Ashikari M Ueguchi-Tanaka M Itoh H Nishimura A Swapan D Ishiyama K Saito T Kobayashi M Khush GS Kitano H Matsuoka M 《Nature》2002,416(6882):701-702
The chronic food shortage that was feared after the rapid expansion of the world population in the 1960s was averted largely by the development of a high-yielding semi-dwarf variety of rice known as IR8, the so-called rice 'green revolution'. The short stature of IR8 is due to a mutation in the plant's sd1 gene, and here we identify this gene as encoding an oxidase enzyme involved in the biosynthesis of gibberellin, a plant growth hormone. Gibberellin is also implicated in green-revolution varieties of wheat, but the reduced height of those crops is conferred by defects in the hormone's signalling pathway. 相似文献
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The origin of multiple superconducting gaps in MgB2 总被引:3,自引:0,他引:3
Souma S Machida Y Sato T Takahashi T Matsui H Wang SC Ding H Kaminski A Campuzano JC Sasaki S Kadowaki K 《Nature》2003,423(6935):65-67
Magnesium diboride, MgB2, has the highest transition temperature (T(c) = 39 K) of the known metallic superconductors. Whether the anomalously high T(c) can be described within the conventional BCS (Bardeen-Cooper-Schrieffer) framework has been debated. The key to understanding superconductivity lies with the 'superconducting energy gap' associated with the formation of the superconducting pairs. Recently, the existence of two kinds of superconducting gaps in MgB2 has been suggested by several experiments; this is in contrast to both conventional and high-T(c) superconductors. A clear demonstration of two gaps has not yet been made because the previous experiments lacked the ability to resolve the momentum of the superconducting electrons. Here we report direct experimental evidence for the two-band superconductivity in MgB2, by separately observing the superconducting gaps of the sigma and pi bands (as well as a surface band). The gaps have distinctly different sizes, which unambiguously establishes MgB2 as a two-gap superconductor. 相似文献