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The vibration of an infinite membrane supported by a squareor triangular array of circular posts is studied by eigenfunctionexpansion and collocation. The fundamental frequencies are foundto be highly sensitive to both small and large relative postradii b. The singular nature of the frequency as b 0 is expressedin an asymptotic formula. 相似文献
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Secondary metabolites from Tectona philippinensis 总被引:1,自引:0,他引:1
The air-dried leaves of Tectona philippinensis, an endemic and endangered Philippine medicinal plant, afforded 5-hydroxy-3,7,4'-trimethoxyflavone (1), 5,4'-dihydroxy-3,7-dimethoxyflavone (2), squalene (3), a mixture of lupeol (4a) and beta-amyrin (4b), chlorophyllide a (5), and hydrocarbons. Antimicrobial tests on 1 and 2 indicated low antifungal activity against the fungi, Candida albicans and Trichophyton mentagrophytes. Compound 1 was also found to have low antibacterial activity against Escherichia coli and Pseudomonas aeruginosa. 相似文献