排序方式: 共有17条查询结果,搜索用时 31 毫秒
1.
本文综合评述了近年来2-[2-(二环己膦基)苯基]-1-甲基-1H-吲哚(CM-Phos)膦配体及其衍生物在钯催化的交叉偶联反应中的应用, 主要根据不同种类的交叉偶联反应进行系统性分述, 并对该领域的发展前景进行了展望. 相似文献
2.
3.
利用氧化钕和盐酸为原料制得Nd(phen)2Cl3(三氯二邻菲罗啉合钕),测得其光谱特性并以稀土氧化钕、苯甲酸和邻菲罗啉为原料制得绿色液体激光介质钕离子的配合物——NdB3phen(三苯甲酸—邻菲罗啉合钕).利用飞秒激光器,采用单光束Z-扫描法研究了NdB3phen的三阶非线性光学特性.结果表明:当入射飞秒激光脉冲波长为400 nm,峰值功率密度为2.94×1014 W/m2,脉宽为117 fs时,测得样品NdB3phen的非线性折射率为-2.84×10-18 cm2/W|NdB3phen在开孔条件下呈现反饱和吸收现象,测出双光子吸收系数的值为9.11×10-12 m/W.实验结果表明,NdB3phen的双光子吸收系数和非线性折射率随着光强的增强而增大. 相似文献
4.
Summary The effect of temperature and mobile phase composition (methanol-water) on the retention behaviour of an oligomeric series
of n-octylsilyl bonded phases in reversed-phase liquid chromatography has been investigated. Plots of lnk against 1/T (van't Hoff plot) and the enthalpy of transfer (ΔHo) yields linear relationships under the conditions studied. The ΔHo values of the aromatic hydrocarbons and n-alkyl benzoates are higher than those of the polar compounds due to their higher
level of interaction with the stationary phase. A linear plot of ΔHo vs. ΔSo suggest that the retention process, which is essentially controlled by non-specific (dispersive) interactions between the
solutes and the bonded ligands, is identical for all cases evaluated. The existence of similar retention mechanisms is confirmed
by the constant value of the enthalpy-entropy compensation temperature of the columns for a given class of componds. As expected,
decreasing the methanol content (% v/v) of the mobile phase results in increased eluite retention times. The methylene and
phenyl selectivities are found to be independent of the carbon content of the stationary phases and varied only with the eluent
composition. In addition to their high stability under aggressive mobile phase conditions as previously reported, the results
of this study generally showed that the solute retention process on oligomeric phases are similar to those exhibited by the
conventional reversed phases. 相似文献
5.
Akapo SO Wegner M Mamangun A McCrea C Asif M Dussex JC 《Journal of chromatography. A》2004,1046(1-2):211-216
The levels of 2-amino-9H-pyrido[2,3-b]indole (AalphaC or 2-amino-alpha-carboline), 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC or 2-amino-3-methyl-alpha-carboline), 9H-pyrido[3,4-b]indole (norharman), and 1-methyl-pyrido[3,4-b]indole (harman) have been determined in the mainstream smoke condensate from three reference cigarettes, namely Kentucky reference 1R5F, Kentucky reference 2R4F, and CORESTA CM4. The amino-alpha-carbolines, and norharman and harman (beta-carbolines) can be classified as heterocyclic aromatic amines (HAAs) and are listed as biologically active agents in the mainstream smoke of cigarettes. For the analysis, the mainstream smoke condensate from cigarettes was collected on a filter pad, the analytes were isolated using solid-phase extraction (SPE), and quantified without derivatization on a GC-MS. Total amounts of carbolines found in the condensate increased from ultralight 1R5F to full-flavor CM4 cigarettes. The level of harman was about 250 ng/cigarette for the 1R5F cigarette and about 1025 ng/cigarette for the CM4 cigarette. Norharman was typically three times more abundant than harman. The AalphaC was found at about 10 times lower level compared to harman, and MeAalphaC was about 50 times lower than harman. The use of reference cigarettes can provide a common measure for laboratories to assess carboline amounts among cigarette brands. 相似文献
6.
SO 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2009,26(5):1897-1924
Let be a bounded Lipschitz domain and consider the energy functional with p]1,∞[ over the space of measure preserving maps In this paper we introduce a class of maps referred to as generalised twists and examine them in connection with the Euler–Lagrange equations associated with over . The main result is a surprising discrepancy between even and odd dimensions. Here we show that in even dimensions the latter system of equations admit infinitely many smooth solutions, modulo isometries, amongst such maps. In odd dimensions this number reduces to one. The result relies on a careful analysis of the full versus the restricted Euler–Lagrange equations where a key ingredient is a necessary and sufficient condition for an associated vector field to be a gradient. 相似文献
7.
WYETH Paul 《中国科学:化学》2010,(3)
Silks represent some of the most precious ancient and historic textile artefacts in collections worldwide.Their optimum preservation demands an appreciation of their characteristics.One important concern,especially with regard to ancient Chinese silks,is whether the fabrics have been degummed.Silks with remnant sericin gum coating the fibroin fibres would require different conservation protocol.In previous research on aged silks,the presence of sericin has been inferred from amino acid analysis of hydrolysa... 相似文献
8.
SO 《Reports on Mathematical Physics》1984,20(3):365-372
The invariants of the non-degenerate representations of the group of pseudo-orthogonal matrices SO(p, 1) are constructed. 相似文献
9.
112高速电影经纬仪是一种新型的高速光电跟踪测量设备,可用于快速飞行目标的轨迹测量和姿态记录,单台完成定位,并有实时输出的功能。该设备与传统的电影经纬仪相比,具有明显的特点,它采用双反射镜跟踪的结构方式,减少了运动部分的惯量,并提高同步数据采集处理速率到200次/秒和高速同步摄影频率到200f/s,有利于高速跟踪测量。该设备采用电视跟踪、计算机程序控制、单杆操纵等多种跟踪方式,可根据不同的目标特性方便地选用或组合使用,可靠地完成对目标的自动捕获和跟踪测量,最大跟踪速度为90°/秒,最大跟踪加速度为90°/秒2。本文还介绍了该设备在靶场使用情况。 相似文献
10.