Molecularly imprinted monolithic stationary phases for liquid chromatographic separation of enantiomers and diastereomers

The method for preparation of molecularly imprinted monolithic stationary phase has been improved to achieve liquid chromatographic separation of enantiomers and diastereomers. By adopting low polar porogenic solvents of toluene and dodecanol and optimal polymerization conditions, the molecularly imprinted monolithic stationary phases with good flow-through properties and high resolution were prepared. Enantiomers of amino acid derivatives and diastereomers of cinchona alkaloids were completely resolved using the monolithic stationary phases. The influence of porogenic composition, monomer-template ratio and polymerization conditions on the chromatographic performance was investigated. Some chromatographic conditions such as the composition of the mobile phase and the temperature were characterized. Scanning electron microscopy showed that the molecularly imprinted monolithic stationary phase has a large through-pore structure to allow the mobile phase to flow through the column at very low backpressure. Accelerated separations of enantiomers and diastereomers were therefore achieved at elevated flow rates. Finally, the chiral recognition performance of the prepared stationary phase in aqueous media was investigated. Hydrophobic interaction, and ionic and/or hydrogen bonding interactions were proposed to be responsible for the recognition mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.

Migration of neutral solutes by double stepwise gradient elution in capillary electrochromatography

Characteristics of electroosmotic flow (EOF) and the migration of neutral solutes under double stepwise gradient elution in capillary electrochromatography were studied systematically. EOF velocity proved to be the function of operation time changing with the introduction of the second mobile phase. Accordingly, the retention of components also changed. The migration of neutral solutes was studied under the following three situations; A, components eluted when the column was filled only with the first kind of mobile phase; B, solutes eluted still in the first kind of mobile phase while at that time two kinds of mobile phase coexisted in the column and C, samples eluted in the second kind of mobile phase. Equations to describe the retention times of components under these three kinds of conditions were deduced and applied to predict the retention times of 12 aromatic compounds. Relative errors between experimental and calculated values were below 5.0%, which proved the reliability of the equations. In addition, parameters that might affect the retention time of solutes, such as the transferring time of mobile phase vials, the capacity factors of components and EOF velocities two steps were studied systematically (C) 2001 Elsevier Science B.V. All rights reserved.

接种根瘤菌对刺槐生长的影响

以刺槐根瘤菌接种于刺槐小苗的研究表明，接种刺槐的株高、地径、根瘤、生物量分别比对照平均增加１３．８、１４．７、３２．８、２４．８％，植株含Ｎ量比对照增加２０—４０％．液体根瘤菌剂及其与ＶＡ首根孢子土双接种效果明显，其生物量分别增加约２０和４０％．

辽西低山丘陵地区水平槽防治水土流失的研究

采用野外调查、定位实验和室内分析相结合的方法 ,通过水平槽与鱼磷坑、荒坡防治水土流失的比较 ,研究了水平槽工程及其生物措施防治低山丘陵地带的水土流失所起的作用 .结果表明 ,水平槽工程利用截水埂拦截径流 ,通过增大土壤入渗速率和延长入渗时间 ,蓄积更多的水分 ;结合植树种草减少蒸发 .水平槽在截获径流的同时 ,也使径流携带的有机无机物质沉积在槽内 ,参与土壤的进一步发育 ,改善当地的农业生态环境 .

啤酒酿造中野生酵母的研究

啤酒酿造中野生酵母的研究吴文芳，张成刚，吕安国，李波（中国科学院沈阳应用生态所）金连武，蒋玲，孙喜春（辽宁铁岭市清河啤酒厂）所谓野生酵母，是指在啤酒酿造过程中出现的除培养酵母之外的所有酵母而言。威尔斯对野生酵母的定义是：任何未经严密选用与控制的酵母，...

沈阳张士灌区常见木本植物镉积累特征

[目的]研究沈阳张士灌区几种常见木本植物对镉的积累特征。[方法]以位于沈阳市张士灌区的德胜乡苗圃为研究样地,比较分析6种木本植物对镉的吸收和累积特性以及对土壤镉的去除能力。[结果]木本植物对土壤中镉的吸收在分类学上表现出规律性差异,即杨、柳>杏、李>刺槐、侧柏。镉在木本植物组织或器官中的分布特征为:根系镉含量低于茎叶,木质部镉含量低于叶片和韧皮部;杨、柳地上部的镉富集系数高(分别为2.19和6.23),在土壤中镉的平均含量为4.56 mg/kg的情况下,每年至少可分别累积20.20和32.68mg/m2的镉,分别占土壤总镉量的1.64%和2.66%。[结论]杨树和柳树是较为理想的修复张士灌区污染土壤的植物种类。

线虫群落结构对外源添加不同浓度铜污染物的响应

通过盆栽模拟试验的方法研究外源添加铜对土壤线虫群落结构的影响,试验添加Cu浓度分别为50 mg kg-1,100 mg kg-1,200 mg kg-1,400 mg kg-1干土和不施加污染物的对照处理,在小麦的生长关键期取样。试验结果表明:线虫不同营养类群对铜污染物的响应在小麦拔节期比较明显,拔节期捕食/杂食线虫的数量在外源添加400 mg kg-1Cu处理中显著低于对照,而不同浓度铜对食细菌线虫和食真菌线虫的影响则表现为低浓度促进高浓度抑制。线虫的生态指数对不同浓度铜污染物反映比较敏感,在小麦苗期和拔节期,与对照相比,不同浓度铜处理中线虫多样性降低,而优势度增加;自由生活线虫成熟度指数对不同浓度铜反映相对滞后,只在小麦成熟期表现出差异,即高浓度铜处理中线虫成熟度指数显著低于对照。

U3D文件格式及运行机制剖析

通用三维文件格式(U3D)是一种可扩展的三维数据文件格式,其目的是为了使下游的3DCAD数据重用和可视化。它主要嵌入到其它文件格式中来显示三维数据,因此在许多主流的应用程序中极为有用。详细分析了这种文件格式及其运行机制,并通过一个写U3D文件的编程实例来进一步说明文件的构造方式。最后,还探讨了这种文件格式的优点及其应用。

太阳辐射对长白山阔叶红松林净生态系统碳交换的影响

太阳辐射是植物进行光合作用的前提条件,因此成为影响植被吸收大气CO2的重要环境因子。该研究基于30min通量和常规气象数据,以相对辐射和晴空指数为指标,分析了2003～2006年生长旺季(6～8月)太阳辐射的改变对长白山阔叶红松(Pinuskoraiensis)林净生态系统碳交换(Netecosystemexchange,NEE)的影响。结果表明:天空有一定云层的覆盖对阔叶红松林碳的净吸收有明显的促进作用。4年里6～8月间生态系统最大光合速率在天空有云覆盖时较晴空条件下分别提高了34%、25%、4%和11

Hydrogenation of o-chloronitrobenzene to o-chloroaniline over Pd/C in supercritical carbon dioxide

Hydrogenation of o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) with Pd/C has been investigated in supercritical carbon dioxide (scCO(2)) at 308 K. The influences of several parameters such as CO2, H-2 pressures, Fd metal particle size and reaction time have been discussed. CO2 pressure presented markedly effects on the reaction rate and product selectivity under the reaction conditions used, the selectivity to o-CAN at CO2 pressure from 8 to 13 MPa (supercritical region) was larger than that at CO2 pressure below 6 MPa (subcritical region).