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41.
采用电镜和金相等手段,对加稀土氧化物和不加稀土氧化物的堆焊金属中的夹杂物进行了研究,结果表明,稀土氧化物能细化堆焊金属中的夹杂物,减少了尺寸大的夹杂物数量,使其尺寸分布在8μm以下,同时,稀土氧化物能够改善夹杂物的形状,减少了形状系数大的长条状夹杂物数量,使形状系数接近为1的夹杂物较多。稀土氧化物还能变质堆焊金属中夹杂物的属性,可以形成铝、硅、镧的氧化物夹杂和铝、硅、镧的硫氧化物夹杂,并且减少了有害的硫化锰和铝、锰、钛复合夹杂物在堆焊金属中的存在。 相似文献
42.
43.
固化土力学强度指标与固化土结构变化的关系是盐渍土特性研究中的重要问题。选取颗粒粒度分维D_(ps)、颗粒定向分维D_(di)、等效直径D_e为试验因素,利用响应曲面法进行试验。响应曲面模型可以对固化土的力学性能指标进行分析和预测,利用该模型研究石灰固化盐渍土的力学强度指标与最优微结构参数之间的关系,并进行了验证。结果表明,固化土微结构最优指标是粒度分维D_(ps)为0.8、颗粒定向分维D_(di)为0.93、等效直径D_e为1.75时,固化土无侧限抗压强度q达到1.636 MPa,与实测值仅相差0.038 MPa;黏聚力c为456.7 k Pa,与实测值完全一致;内摩擦角为39.6°,与实测值仅相差0.2°。该模型为探讨各类固化盐渍土物理化学指标、各掺加料比例及固化土微结构之间相互关系提供了借鉴和依据。 相似文献
44.
对外消旋体药物进行分离拆分是获取手性药物的重要方法。探讨了环糊精体系包结拆分法的机理,并对运用其机理于手性药物分离中的应用作了探讨。 相似文献
45.
江苏省耐盐生物质能源植物选育和生物柴油制备研究 总被引:2,自引:0,他引:2
江苏省有近67万公顷沿海盐土滩涂资源,发展适应这些土地资源的油料植物对促进江苏省生物质能的产业化具有极大的促进作用.本研究针对江苏省土地资源的特点,自2001年,从江苏盐城种植了近10年的美国耐盐油料植物海滨锦葵6万株自然群体中筛选了40个优良单株,并进行了子代测定.目前已经初步选育出了海滨锦葵优良无性系,含油量从原群体平均的18 %提高到23 %.2005年首次从耐盐油料植物海滨锦葵中成功获得生物柴油实验室样品,并已经得到中石化权威机构检测数据. 相似文献
46.
The crystal structure of urea-polyethylene complex in the hexagonal form, obtained by one of our preparation methods, is analysed by X-ray power diffractometry. In this analysis, the fixed molecular parameters of urea are used, and three models with respect to rotational disorder of the guest polyethylene molecule are assumed. It is shown that the host lattice structure constructed by urea molecules is essentially the same as that of urea-n-paraffin complex. Effects of the disorder structure of the guest on X-ray scattering of the complex are presented. However, there is a difficulty in identifying the disorder structure by X-ray analysis. With the aid of a potential energy calculation between the hexagonal urea tunnel and the guest molecule, a rotational disorder model is preferred. 相似文献
47.
48.
M. Cartens E. Molina Grima A. Robles Medina A. Giménez Giménez J. Ibáñez González 《Journal of the American Oil Chemists' Society》1996,73(8):1025-1031
Eicosapentaenoic acid (EPA, 20∶5n-3) was obtained from the marine microalgaePhaeodactylum tricornutum by a three-step process: fatty acid extraction by direct saponification of biomass, polyunsaturated fatty acid (PUFA) concentration
by formation of urea inclusion compounds, and EPA isolation by semipreparative high-performance liquid chromatography (HPLC).
Alternatively, EPA was obtained by a similar two-step process without the PUFA concentration step by the urea method. Direct
saponification of biomass was carried out with two solvents that contained KOH for lipid saponification. An increase in yield
was obtained because the problems associated with emulsion formation were avoided by separating the biomass from the soap
solution before adding hexane for extraction of insaponifiables. The most efficient solvent, ethanol (96%) at 60°C for 1 h,
extracted 98.3% of EPA. PUFA were concentrated by the urea method with a urea/fatty acid ratio of 4∶1 at a crystallization
temperature of 28°C and by using methanol and ethanol as urea solvents. An EPA concentration ratio of 1.73 (55.2∶31.9) and
a recover yield of 78.6% were obtained with methanol as the urea solvent. This PUFA concentrate was used to obtain 93.4% pure
EPA by semipreparative HPLC with a reverse-phase, C18, 10 mm i.d.×25-cm column and methanol/water (1% acetic acid), 80∶20 w/w, as the mobile phase. Eighty-five percent of EPA
loaded was recovered, and 65.7% of EPA present inP. tricornutum biomass was recovered in highly pure form by this three-step downstream process. Alternatively, 93.6% pure EPA was isolated
from the fatty acid extract (without the PUFA concentration step) with 100% EPA recovery yield. This two-step process increases
the overall EPA yield to 98.3%, but it is only possible to obtain 20% as much EPA as that obtained by three-step downstream
processing. 相似文献
49.
通过构造砂页岩互层结构,并根据渗透率对砂岩层岩性进行分类,建立了多岩相非均质模型,利用多组分多相流数值模拟软件TOUGH2/ECO2N探究二氧化碳注入深部互层咸水层后的分布特征,结果显示二氧化碳聚集在低渗透性的页岩层底部,呈分层结构,砂岩层中优先在渗透率较高的岩相中运移并呈分散分布;超临界二氧化碳不断溶于地层水,含饱和二氧化碳的咸水密度增加并缓慢下沉,无明显分层现象。 相似文献
50.
Supramolecular assemblies from chitosan-graft-β-cyclodextrin (CS-g-CD) and benzimidazole ended poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL-BM) were formed based on the inclusion complexation between β-cyclodextrin and benzimidazole. The supra-amphiphiles self-assembled into complex vesicles with PCL/β-CD as the hydrophobic membrane, hydrophilic PEG and CS as the corona. The hydrophobic membrane and aqueous lumen of vesicles exhibited efficient entrapment both for hydrophobic curcumin (CUR) and hydrophilic doxorubicin (DOX). The drug loading of vesicles was more than 20.2% and 38.4% for CUR and DOX, respectively. Decreasing pH to acidic condition or increasing temperature, more controllable and rapid release of two drugs was observed. Cytotoxicity assays revealed that dual drug-loaded vesicles retained high cell proliferation inhibition efficiency than free drugs.GRAPHICAL ABSTRACT 相似文献