相转移催化合成11-脱氧甘草次酸-3-位酯类衍生物

以甘草次酸为原料 ,经还原制得 1 1 -脱氧甘草次酸 ,然后在聚苯乙烯固载化聚乙二醇 40 0( PS- PEG- 40 0 )的催化下。合成了七种具有潜在药理活性和应用前景的 1 1 -脱氧甘草次酸 - 3-位酯类衍生物。合成方法简单 ,产率较高 ,后处理方便     

Durability of fire retardant treated wood products at humid and exterior conditions review of literature

Fire retardants may considerably improve the fire properties of wood products, but the durability, e.g. in exterior applications, has not been addressed fully. This paper reviews the existing knowledge and experience mainly from the USA with the aim of supporting further development in Europe. The review is concentrated on pressure impregnated fire retardant treated wood products which have the best opportunities for increased durability. Copyright © 2001 by John Wiley & Sons, Ltd.     

左旋麻黄素半生物合成研究Ⅲ.L-苯基乙酰基甲醇的提取技术

对固相生物合成的L PAC(左旋麻黄素前体 )提取技术进行了研究。结果表明 ,采用H型大孔吸附树脂从生物合成的反应产物中提取L PAC最佳。当样品液pH为 6左右、过柱流速为0 2～ 0 3BV/min、柱直径与树脂高度比为 1 5∶11,用质量分数为 70 %丙酮水溶液洗脱 ,该大孔吸附树脂对L PAC的动态吸附量为 6 1 6 9mg/g。洗脱的丙酮水溶液经减压浓缩 ,获油状L PAC粗品 ,其质量浓度不低于 0 2 4g/mL     

Autogenous deformation and RH-change in perspective

Autogenous deformation and change of the relative humidity (RH-change) have been described and registered for a century. However, it is only within the last decade that these phenomena have received appreciable attention. The reason for this is that autogenous deformation and autogenous RH-change are phenomena of special importance within high-strength (high-performance) concrete technology, and a significant utilisation of these concretes did not take place until the early 1980s. In the present paper an historical overview of autogenous deformation and RH-change is given. In addition, due to the present status of this research field both terminology and measuring techniques are described in detail. Finally, some expectations for future research in this field are given.     

温度对胎面材料压缩力学性能影响规律研究

环境温度对轮胎胎面材料力学性能有重要影响,它直接影响接地性能。为获取不同温度下胎面橡胶材料的压缩力学性能,进行了准静态单轴压缩实验。基于此,获取不同温度、不同速度下的应力-应变关系,揭示温度及应变率对其压缩力学性能的影响规律。采用Mooney-Rivlin本构模型来表征胎面橡胶压缩荷载下的力学行为。结果表明,在低应变率时应变率的影响不明显;在20-90℃温度范围内,随着温度的升高,橡胶压缩模量减小。Mooney-Rivlin本构模型拟合与实验结果相符,它为不同温度下胎面橡胶压缩性能分析奠定理论基础。     

Dispersion polymerization of styrene in CO2-expanded ethanol

Dispersion polymerization of styrene has been performed in CO₂-expanded ethanol at ≤9 MPa and 70 °C using PVP as stabilizer. The polymerizations proceeded with good colloidal stability, resulting in spherical particles of diameters of ∼2 μm. Pressurization with CO₂ leads to an increase in particle size (∼1 μm in the corresponding CO₂-free system), and a decrease in both polymerization rate and molecular weight. The main effect of CO₂ is proposed to be its influence on the partitioning of monomer between the continuous and the particle phase–the results indicate that CO₂-pressurization causes a reduction in monomer concentration in the particles. Overall, the results are consistent with literature data on the effects of the polarity of the continuous phase in dispersion polymerization of styrene in alcohols and alcohol/water mixtures.     

Characterization of Particulate Matter from Direct Injected Gasoline Engines

The reactivity and reaction kinetics of particulate matter (PM) from direct injected gasoline (GDI) engines has been studied by O₂ and NO₂ based temperature programmed and isothermal step-response experiments, and the PM nano-structure has been characterized using HRTEM. The reactivity of the PM samples collected in filters during on-road driving was found to increase in the following order: Printex U < diesel < gasoline PI ≈ gasoline DI < ethanol for O₂ based combustion. The activation energies for O₂ and NO₂ based oxidation of PM collected from a GDI engine in an engine bench set-up was estimated to 146 and 71 kJ/mol respectively, which is comparable to corresponding values reported for diesel and model soot. Similar nano-structure features (crystallites plane dimensions, curvature and relative orientation) as observed for diesel soot were observed for gasoline PM.     

Dietary Fat in Relation to Erythrocyte Fatty Acid Composition in Men

Erythrocyte membrane fatty acid (EMFA) composition is used in the validation of food frequency questionnaires (FFQ) and the evaluation of dietary fat quality. In this cross-sectional study we aimed to investigate associations of diet with EMFA. Altogether, 1,033 randomly selected Finnish men, aged from 47 to 75 years filled in a FFQ and their EMFA composition was analyzed. Marine polyunsaturated fatty acid (PUFA) intake correlated positively with erythrocyte eicosapentaenoic and docosahexaenoic acids (r _s = 0.415 and r _s = 0.340, respectively, P < 0.001) and inversely with all n-6 PUFA analyzed (P < 0.001). PUFA intake from spreads and cooking fats correlated positively with alpha-linolenic (ALA), linoleic (LNA) and nervonic acids (r _s = 0.229, r _s = 0.160 and r _s = 0.143, respectively, P < 0.001). Milk fat intake was associated with myristic and behenic acids (r _s = 0.186 and r _s = 0.132, respectively P < 0.001). Butter users had lower ALA and LNA proportions (mol%) than non-users (0.16 ± 0.04 vs. 0.19 ± 0.05, P < 0.001 and 7.77 ± 1.02 vs. 8.12 ± 1.11, P = 0.001). Higher PUFA intake from meat was related to decreased long-chain n-3 (P < 0.001) and increased n-6 PUFA (P < 0.001) proportions. In conclusion, EMFA composition reflects particularly well the intakes of n-3 PUFA, whereas other associations remained lower. Yet, all main sources of dietary fat were related with EMFA. The dietary effect on the nervonic acid proportion was confirmed.