Synthesis of monomethylated dioscin derivatives and their antitumor activities

All possible eight monomethylated dioscin derivatives (1-8) were synthesized. Their inhibitory activities against P388 and A-549 cells were determined, and the results indicate that six of the eight hydroxyls of dioscin are the 'key polar groupings' for tumor inhibitory activities. (C) 2002 Elsevier Science Ltd. All rights reserved.

云雾山封育草原对表土持水性的影响

应用离心机法测定土壤水分特征,研究黄土高原典型草原带退耕地植被恢复演替过程中土壤持水性能的变化特点及趋势。结果表明:土壤含水量与土壤水吸力之间符合幂函数θ=aSb,参数a的变化随着植被的演替呈增加趋势;由于植被的影响,在同一吸力范围内的土壤含水量不同,植被为顶级长芒草(Stipabungeana)群落时,土壤在各吸力段的含水量最高,坡耕地最低;其它群落土壤含水量随着水吸力的增加变化趋于一致;退耕地植被在演替过程中通过提高土壤有机质含量改善结构,降低容重并增加毛管孔隙度,对土壤的储水和持水性能产生作用。

食用菌液体菌种的发展与应用

食用菌产业是我国重要的农业产业之一,也是提高农业生产水平和农民收入重要途径。但应用传统菌种进行生产周期较长,且不便于后期管理和操作。应用食用菌液体菌种进行生产能显著提高食用菌的产量和质量,便于食用菌的工厂化和标准化生产。本文综述了食用菌液体菌种的优势,发展状况以及发展前景。

水磷耦合效应对玉米苗期生长和水分利用效率的影响

利用Hogland全磷和缺磷处理进行了室内砂培桶栽试验 ,研究了玉米 5叶期前的生长状况、生理特性、水分消耗、干物质积累与分配及水分利用效率 .结果表明 ,水磷耦合效应取决于水分的供应方式 ,以干湿交替施磷效果最佳 ,其次为干旱施磷 ,再次为湿润施磷处理 .干湿交替施磷能显著提高光合速率 ,增加作物气孔导度 ,促进根系生长 ,增加根冠比 ,调节整株水平下干物质资源的合理分配 ,提高玉米苗期水分利用效率 .

微生物菌剂在鸡粪有机肥料堆制发酵中的应用

降解鸡粪的微生物菌剂是由蛋白分解菌、纤维分解菌、酵母菌、光合细菌、乳酸菌等多种有益微生物组成。这些菌群在生长中产生的代谢物质相互利用,而不发生拮抗现象。在鸡粪堆制发酵过程中微生物菌群以辅料为载体与鸡粪组成了复杂而稳定的微生态系统,能够快速、环保地发酵鸡粪并增加肥效。介绍了微生物菌剂在鸡粪堆肥中的作用、机理、发酵工艺及研究现状。

青藏高原农牧业发展方向思考

青藏高原是我国乃至世界自然、人文、生态环境最具特色的区域之一,高原独特的地理环境及其资源条件,客观上决定了其地表资源利用的主体方式是农牧业。随着我国加入WTO后市场经济的快速发展,生态环境保护建设的日益重视以及青藏铁路二期工程的顺利建设,使高原农牧业发展的区内外环境发生了历史性的变化。这种变化将给高原农牧业提供前所未有的发展机遇,同时也提出了更为严峻的挑战。未来青藏高原农牧业的发展应当采取一种全新的思路,重点实现以下几个战略性转变:粮食供应由"自给"向"自主"的转变,重新建立新的粮食安全观;农牧业由"增产

Synthesis and characterization of Prussian blue@platinum nanoparticle hybrids from a mixture solution of platinum nanocatalyst and ferric ferricyanide

In the present study, platinum nanoparticles modified with Prussian blue (PB) have been synthesized by a heterogeneous catalytic reaction. Transmission electronic microscopy (TEM) confirmed the deposition of nanoclusters around the Surfaces of platinum particles, and spectroscopic studies verified that the molecular composition of the nanoclusters was dominantly PB and a minority of platinum ferricyanide. Thus, it was shown that the platinum particles behaved not only as catalysts for the growth of PB, but also as a reactant to generate a PB analogue complex.

Super-hydrophobicity of silica nanoparticles modified with vinyl groups

Super-hydrophobic films with vinyl-modified silica nanoparticles (V-SiOx-NPs) were successfully prepared. The rough surface, which was composed of microstructures of disordered V-SiOx-NPs and nanostructures on the surface of V-SiOx-NPs, rather than the chemical composition devoted to the super-hydrophobicity of film. The relationship between contact angle and diameter of V-SiOx-NPs was then investigated. The sessile contact angles (CA) of films with 150-1600nm V-SiOx-NPs were around 166 regardless the diameter, while the film with 85 nm V-SiOx-NPs had the lowest CA of about 158. The packing manner of V-SiOx-NPs determined the air fraction on the surface and then the CA.

A novel white light emitting long-lasting phosphor

A novel white light emitting long-lasting phosphor Cd1-xDyxSiO3 is reported in this letter. The Dy3+ doped CdSiO3 phosphor emits white light. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254 nm UV irradiation have been removed for about 30 min. In the emission spectrum of 5% Dy3+ doped CdSiO3 phosphor, there are two emission peaks of Dy3+, 580 mn (F-4(9/2)-->H-6(13/2)) and 486 nm (F-4(9/2)-->H-6(15/2)), as well as a broad band emission located at about 410 nm. All the three emissions form a white light with CIE chromaticity coordinates x=0.3874, y=0.3760 and the color temperature is 4000 K under 254 mn excitation. It indicated that this phosphor is a promising new luminescent material for practice application.