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排序方式: 共有451条查询结果,搜索用时 265 毫秒
441.
研制一种能够快速检测和筛选细菌以及病毒微生物,并且能够对动物体内致病载体进行现场监测的完整的微分析装置具有十分重大的意义.这种便携式的生物分析系统不需要繁杂的仪器设备就能进行复杂的生物样品分析,并由一般的未经训练的个体在短时间内完成操作过程. 相似文献
442.
合成了一种新颖的油溶性C60-丙烯酸月桂酯共聚物,采用四球摩擦磨损试验机、扫描电子电镜研究了其作为液体石蜡润滑添加剂的摩擦学特性,结果表明,C60-丙烯酸月桂酯共聚物可提高石蜡基础液的抗磨性能,改善微观磨损状态. 相似文献
443.
遗传算法在结构优化中的研究进展 总被引:30,自引:1,他引:29
遗传算法(genetic algorithm)是基于Darwin的进化论和Mendal遗传学说而形成的新算法,具有全局收敛性和并行性,适用性广,并要求较少的先验知识,现在已广泛应用于优化、模式识别等方面.本文简要地介绍了简单遗传算法的基本过程及其数学基础;并从编码机制、收敛性和算子的研究等方面详细地阐述了遗传算法理论的发展;对约束处理方式、适应值函数的选取等方面的研究进行分析和评论;最后还提出遗传算法存在的主要问题和展望. 相似文献
444.
用超临界流体萃取及GC-MS分析了新冷冻干燥及保存15d,30d,45d,60d,75d,90d后的鲜牡蛎粉中的23种脂肪酸组分的质量分数。发现在存放过程中牡蛎脂肪酸的稳定性与其不饱和度有关;不饱和度越高,脂肪酸越易被氧化,其中多不饱和记酸的氧化是逐渐进行的,没有特定的稳定期。 相似文献
445.
446.
Jinmao You Wenjian Lao Qingyu Ou Xuejun Sun 《Fresenius' Journal of Analytical Chemistry》1999,365(6):521-528
A simple and sensitive HPLC method for the determination of hydroxyl compounds including volatile alcohols from spiked plasma,
using a fluorescent condensation agent, namely carbazole-9-N-(2-methyl)-acetyl-benzene-disulfonate (CMABS), has been developed.
A mixture of alcohols and pyridine in dichloromethane was treated with CMABS to give a quantitative yield of esters. The maximum
fluorescence emissions for the derivatized alcohols are at 365 nm (λex 335 nm). Studies on derivatization conditions indicate that alcohols react very fast with CMABS in presence of pyridine in
dichloromethane to give the corresponding fluorescent derivatives. The method, in conjunction with a multi-step gradient,
offers a baseline resolution of the common alcohol derivatives on a reversed-phase C18 column, which is more convenient and more efficient than previous methods which require the prior conversion of the carboxylic
acids to the acyl chlorides. The application of this method to the analysis of volatile alcohols in plasma was also investigated.
The LC separation shows good selectivity and reproducibility for alcohol derivatives. The relative standard deviations ?(n = 5) for 100 pmol of each alcohol are < 4%. The detection limits are at the fmol level for C1–C3 alcohols and pmol level for C4–C9 alcohols.
Received: 9 November 1998 / Revised: 3 May 1999 / Accepted: 6 May 1999 相似文献
447.
Summary We report four new derivatization agents, acridone-N-acetic acid (ARC), carbazole-9-ylacetic acid (CRA), carbazole-9-ylpropionic acid (CRP), and 2-methyl-2-carbazole-9-ylacetic
acid (MCRA), with strong fluorescence emission which has low dependence on solvent polarity. The emission maxima for ARC,
CRA, CRP, and MCRA were 430 nm (λex 404 nm), 368 nm (λex 335 nm), 356 nm (λex 340 nm) and 360 nm (λex 330 nm), respectively. The effects of mobile-phase composition, pH, and temperature on the liquid chromatographic retention
behavior of the four fluorescence agents were investigated. An experimental model was established for calculating the inclusion
constants of cyclodextrin (CD) complexes in the dynamic state, using β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin
(HP-β-CD) as examples, and different mobilephase compositions. On the basis of the model, the inclusion constants of the solutes
in pure water (K
fw) were determined by extrapolation. The thermodynamic parameters (ΔH
o and ΔS
o) and dissociation constantsK
am for the solutes in this chromatographic system were obtained by means of capacity factor (k) values using a corresponding model formulation. 相似文献
448.
研究了MgB2超导薄膜正常态电阻的影响因素,探讨了与之相应的超导电性机制。MgB2超导薄膜样品采用两步异位退火的Mg扩散方法制备,通过电阻~温度曲线测量、扫描电子显微镜形貌观测和光学金相显微镜观察等方法研究了所制备薄膜的基本特性。实验结果表明,先驱硼薄膜的纯度严重影响着所生成的MgB2超导薄膜的转变温度,退火温度越高,影响越大;退火温度高的样品,正常态电阻大;退火时间长的样品正常态电阻大。 相似文献
449.
Xiaoqiang Xue Fang Li Wenyan Huang Hongjun Yang Bibiao Jiang Yiliang Zheng Dongliang Zhang Jianbo Fang Lizhi Kong Guangqun Zhai Jianhai Chen 《Macromolecular rapid communications》2014,35(3):330-336
The novel hyperbranched poly(methyl acrylate)‐block‐poly(acrylic acid)s (HBPMA‐b‐PAAs) are successfully synthesized via single‐electron transfer‐living radical polymerization (SET‐LRP), followed with hydrolysis reaction. The copolymer solution could spontaneously form unimolecular micelles composed of the hydrophobic core (PMA) and the hydrophilic shell (PAA) in water. Results show that the size of spherical particles increases from 8.18 to 19.18 nm with increased pH from 3.0 to 12.0. Most interestingly, the unique regular quadrangular prisms with the large microstructure (5.70 μm in length, and 0.47 μm in width) are observed by the self‐assembly of unimolecular micelles when pH value is below 2. Such self‐assembly behavior of HBPMA‐b‐PAA in solution is significantly influenced by the pH cycle times and concentration, which show that increased polymer concentration favors aggregate growth.
450.
Dr. Qimin Jiang Hongyan Zhang Lingyue Shi Shuyi Guan Prof. Wenyan Huang Dr. Xiaoqiang Xue Dr. Hongjun Yang Dr. Li Jiang Prof. Bibiao Jiang 《European journal of organic chemistry》2023,26(8):e202201419
Nontraditional small organic luminogens (NTSOLs) without classic conjugated chromophores have attracted significant attention. However, the design and synthesis of NTSOLs with fluorescence in the red region remain significantly challenging. In this study, we established a self-catalyzed hydroxyl-yne click reaction for preparing long-wavelength and red-emitting NTSOLs. Owing to their perfect reaction selectivity, high efficiency, and excellent universality, a series of compounds with well-defined structures were obtained in high yields. Moreover, the obtained compounds showed concentration-enhanced and excitation-dependent emission characteristics. The compounds also exhibited dramatical chemical structure-dependent and aggregation-induced red-shifted fluorescence properties, based on which we successfully obtained red-emitting NTSOLs by simply adjusting chemical structure and concentration. Also, the compounds show good cell staining ability, which can be used in cell imaging. 相似文献