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211.
芳基三氮烯4-位取代基对抗癌活性影响的构象分析 总被引:1,自引:0,他引:1
传统的药物设计和新药开发主要是依靠随机筛选,这种方法误差大,且需要费大量时间和经费,其结果也经常不能达到预期的设想。即使是一个国际性的大制药集团,每年平均要合成上万个化合物才能从中筛选出一个可以成为商品的新药。这种状况迫使我们去寻找一条新的打破常规的途径研究新药。近年来,随着计算机图形系统的广泛应用,对药物构效关系的研究得到了卓有成效的发展,取得了一些成功的例子。如抗菌抗癌琥珀酰-L脯氨酸就是计算化学与分子图形技术相结合的成果,目前已投放市场。 相似文献
212.
Nix and Gao established an important relation between the microindentation hardness and indentation depth. Such a relation
has been verified by many microindentation experiments (indentation depths in the micrometer range), but it does not always
hold in nanoindentation experiments (indentation depths approaching the nanometer range). Indenter tip radius effect has been
proposed by Qu et al. and others as possibly the main factor that causes the deviation from Nix and Gao's relationship. We
have developed an indentation model for micro- and nanoindentation, which accounts for two indenter shapes, a sharp, conical
indenter and a conical indenter with a spherical tip. The analysis is based on the conventional theory of mechanism-based
strain gradient plasticity established from the Taylor dislocation model to account for the effect of geometrically necessary
dislocations. The comparison between numerical result and Feng and Nix's experimental data shows that the indenter tip radius
effect indeed causes the deviation from Nix-Gao relation, but it seems not be the main factor.
The project supported by the National Natural Science Foundation of China (10121202) and the Ministry of Education of China
(20020003023) 相似文献
213.
薄层层析法分离菊芋汁中低聚糖 总被引:1,自引:0,他引:1
采用薄层层析法(TLC)分离菊芋汁中的低聚糖成分。固定相为硅胶板GF254,展层剂为V正丁醇∶V异丙醇∶V乙酸∶V水=7∶5∶2∶4,显色剂为苯胺(4 mL)-二苯胺(4 g)-磷酸(20 mL)(溶于200 mL丙酮中)试剂。该展层体系可用于快速层析分离菊芋汁中的混合低聚糖,经过两次展层可达到良好分离结果。 相似文献
214.
215.
Huaquan Guan Wenbin Luo Beihua Bao Yudan Cao Fangfang Cheng Sheng Yu Qiaoling Fan Li Zhang Qinan Wu Mingqiu Shan 《Molecules (Basel, Switzerland)》2022,27(10)
Polyphenolic acids are the widely occurring natural products in almost each herbal plant, among which rosmarinic acid (RA, C18H16O8) is well-known, and is present in over 160 species belonging to many families, especially the Lamiaceae. Aside from this herbal ingredient, dozens of its natural derivatives have also been isolated and characterized from many natural plants. In recent years, with the increasing focus on the natural products as alternative treatments, a large number of pharmacological studies have been carried out to demonstrate the various biological activities of RA such as anti-inflammation, anti-oxidation, anti-diabetes, anti-virus, anti-tumor, neuroprotection, hepatoprotection, etc. In addition, investigations concerning its biosynthesis, extraction, analysis, clinical applications, and pharmacokinetics have also been performed. Although many achievements have been made in various research aspects, there still exist some problems or issues to be answered, especially its toxicity and bioavailability. Thus, we hope that in the case of natural products, the present review can not only provide a comprehensive understanding on RA covering its miscellaneous research fields, but also highlight some of the present issues and future perspectives worth investigating later, in order to help us utilize this polyphenolic acid more efficiently, widely, and safely. 相似文献
216.
Zecong Qin Chuyi Huang Z.N.Buck W.Kreuzpaintner S.M.Amir A.Salman Fan Ye Junpei Zhang Chenyang Jiang Tianhao Wang Xin Tong 《中国物理快报》2021,(5):16-20
At the China Spallation Neutron Source(CSNS), we have developed a custom gas-filling station, a glassblowing workshop, and a spin-exchange optical pumping(SEOP) system for producing high-quality ~3He-based neutron spin filter(NSF) cells. The gas-filling station is capable of routinely filling ~3He cells made from GE180 glass of various dimensions, to be used as neutron polarizers and analyzers on beamlines at the CSNS. Performance tests on cells fabricated at our gas-filling station are conducted via neutron transmission and nuclear-magneticresonance measurements, revealing nominal filling pressures, and a saturated ~3He polarization in the region of 80%, with a lifetime of approximately 240 hours. These results demonstrate our ability to produce competitive NSF cells to meet the ever-increasing research needs of the polarized neutron research community. 相似文献
217.
Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. It is shown that the perforation of a thick plate is dominated by several non-dimensional numbers, i.e., the impact function, the geometry function of projectile, the non-dimensional thickness of target and the impact obliquity. Explicit formulae are obtained to predict the ballistic limit, residual velocity and directional change for the oblique perforation of thick metallic plates. The proposed model is able to predict the critical condition for the occurrence of ricochet. The proposed model is validated by comparing the predictions with other existing models and independent experimental data.The English text was polished by Keren Wang 相似文献
218.
219.
等离子体流动控制激励器由于其响应速度快、激励频带宽、能量损耗低、可靠性强的优势,在航空航天领域的主动流动控制等方面得到了广泛应用.文章提出了一种新型的等离子体气动激励器——三电极共面介质阻挡放电激励器,研究了该激励器电极结构对放电特性和诱导气流速度的影响,并与传统共面介质阻挡放电和沿面介质阻挡放电激励器进行了比较.结果表明:(1)随着激励电压的提高,高压电极和地电极之间先出现了丝状放电并逐渐延伸到第三电极;(2)随着第三电极与高压电极之间的距离增大,诱导气流速率从2.4 m/s下降到0 m/s,而第三电极宽度的变动对诱导气流速度影响可忽略不计;(3)相同外部条件下,该激励器诱导的气流速度小于沿面介质阻挡放电激励器,但高于共面介质阻挡放电激励器. 相似文献
220.
在JP10和煤油点火特性激波管实验的基础上,实验研究了硅烷对这两种典型高碳数碳氢燃
料点火特性的影响. 在预加热到70 C的激波管上,采用缝合运行条件获得了近7ms
的实验时间,将实验延伸至低温区. 采用气相色谱分析和高精度真空仪直接测定压力相结合
的方法,确定了燃料气相浓度,解决了高碳数碳氢燃料点火激波管实验时由于管壁吸附影响
燃料气相浓度确定的困难. 实验记录了点火过程中OH自由基发射强度变化,并作为判断点
火发生的标志. 实验温度范围880~1800K, 压力范
围0.16~0.53\,MPa. 当硅烷加入量约为燃料的10%~15%(摩尔比),
质量比为2%~3%, 观测到明显的点火促进作用. 该研究对超燃研究中发动机设计、
燃料选择等方面具有直接的工程意义,也可用于检验燃烧化学动力学模型的合理性. 相似文献