半制备色谱柱装填条件的选择

填充技术是影响柱性能的重要因素,但关于半制备柱装填的报道很少.本论文主要对干法和匀浆法装填的半制备柱(φ10×200mm)的性能进行了对比,并对两种方法的装填条件进行了选择.实验结果表明匀浆法装填柱的重现性和柱性能明显优于干法装填的柱.在匀浆法填充中,乙醇为匀浆溶剂,匀浆体积为120mL,冲洗流速为330mL/min,装填时间为20min时所填柱的性能最好.     

聚苯硫醚副产物浆料的分离及氯化锂的回收研究

聚苯硫醚(PPS)的工业合成采用对二氯苯和硫化钠为原料,N-甲基-2-吡咯烷酮(NMP)为溶剂,氯化锂为助剂,经加压缩聚反应而成.该反应除了获得PPS外,还产生一部分副产物淤浆,有必要对其组成物进行分离回收和资源化利用.本文采用四氢呋喃(THF)为添加剂对这种副产物淤浆进行了分离研究,并对其中的锂盐进行了回收研究.结果表明,采用THF添加剂可以较为容易地将浆料分离为PPS低聚物、NMP以及无机盐,采用有机溶剂提取法可以回收氯化锂,LiCl的回收率可达40%.     

三参数Weibull分布参数的Bayes估计

给出了三参数Weibull分布参数Bayes估计的两种方法,其一基于Laplace数值积分法,其二基于Gibbs抽样方法.模拟例子说明了估计方法的有效性.     

Determination of total arsenic and arsenic (III) in phosphate fertilizers and phosphate rocks by HG-AAS after multivariate optimization based on Box-Behnken design

In the present paper, a procedure for the determination of total arsenic and arsenic (III) in phosphate fertilizers and phosphate rocks by slurry sampling (SS) with hydride generation atomic absorption spectrometry (HG-AAS) is proposed. Arsenic (III) is determinated directly and total arsenic is determinated after reduction reaction. The procedure was optimized for the flow rate of NaBH₄, NaBH₄ and hydrochloric acid concentrations using a full two-level factorial and also a Box-Behnken design. Slurry preparation with hydrochloric acid in an ultrasonic bath allowed the determination of arsenic (III) with limits of detection and quantification of 0.1 and 0.3 μg L⁻¹, respectively. The precision of results, expressed as relative standard deviation (RSD), was always lower than 3%. The accuracy of this method was confirmed by analysis of certified sediment reference materials, while the procedure also allows for calibration using aqueous external standards. This method (SS/HG-AAS) was used to determine total arsenic and arsenic (III) in two phosphate rock samples and two phosphate fertilizer samples. In these samples, total arsenic concentrations varied from 5.2 to 20.0 mg kg⁻¹, while As (III) concentrations varied from 2.1 to 5.5 mg kg⁻¹, in agreement with published values. All samples were also analyzed using acid digestion/HG-AAS. Both, a paired t-test and a linear regression model demonstrated no significant difference (95% CL) between the results obtained using these two sample preparation procedures.     

Determination of heteronuclear coupling constants from 3D HSQC-TOCSY experiment with optimized random sampling of evolution time space

An application of 3D version of HSQC-TOCSY experiment for the measurement of heteronuclear coupling constants of organic compounds yielding complex spectra is proposed. The approach presented here is based on the optimized random sampling of the evolution time space followed by Multidimensional Fourier Transform (MFT). In this study, we show that the interpretation of omega(3)-(13)C coupled (1)H-(13)C 3D HSQC-TOCSY spectra with E.COSY-type multiplets allows one to evaluate heteronuclear coupling constants of strychnine with high accuracy, whereas the employment of 2D methods is associated with signal overlap and use of conventionally recorded 3D NMR spectra cannot provide accurate results in an overnight experiment.     

Closing the side-chain gap in protein loop modeling

The success of structure-based drug design relies on accurate protein modeling where one of the key issues is the modeling and refinement of loops. This study takes a critical look at modeled loops, determining the effect of re-sampling side-chains after the loop conformation has been generated. The results are evaluated in terms of backbone and side-chain conformations with respect to the native loop. While models can contain loops with high quality backbone conformations, the side-chain orientations could be poor, and therefore unsuitable for ligand docking and structure-based design. In this study, we report on the ability to model loop side-chains accurately using a variety of commercially available algorithms that include rotamer libraries, systematic torsion scans and knowledge-based methods. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

基于抽样理论的改进型星座覆盖分析方法

针对传统网格点方法在分析星座对目标区域的覆盖性能时,存在着计算效率不高的问题,利用抽样理论中借助样本统计量对总体参数进行估计的思想,对传统网格点方法加以了改进;通过分析星座对目标区域内所有网格点的覆盖情况与网格点经纬度之间的关系,确立了对所有网格点构成的总体采用先分层后随机的抽样方式,并分析了层的划分和样本量在各层的分配;根据不同指标的统计特征,给出了不同星座覆盖性能指标的估计方法和不同精度条件下总样本量的计算过程,并建立了改进网格点法的实施流程;最后利用改进方法计算了仿真时段内北斗卫星导航系统对某一地面区域的平均PDOP值,通过与传统网格点方法的仿真结果进行比较并对仿真数据进行分析,证明了该改进方法在保证计算精度的同时,有效地提升了计算效率。     

抽运-检测型非线性磁光旋转铷原子磁力仪的研究

报道了一种抽运-检测型的非线性磁光旋转铷原子磁力仪.其原理是线偏振光通过处于外磁场环境中被极化的原子介质后,由于原子对线偏振光中左、右圆偏成分不同的吸收和色散,导致光的偏振方向会产生与磁场相关的转动.分析了该磁力仪的工作原理,并测试了它对不同磁场大小的响应.测试结果表明,磁力仪测量范围为100—100000 nT,极限灵敏度为0.2 p T/Hz~(1/2),磁场分辨率为0.1 p T.进一步研究了不同磁场下原子系综极化态的横向弛豫时间,讨论了原子磁力仪高磁场采样率的获得方法.本文的原子磁力仪在5000—100000 n T的磁场测量范围内磁场采样率可实现1—1000 Hz范围内可调,能够测量低频的微弱交变磁场.本文的研究内容为大磁场测量范围、高灵敏度、高磁场采样率的原子磁力仪研制提供了重要参考.     

抽样法与灵敏度法k_(eff)不确定度量化

核反应堆的中子学模拟计算中,核数据的不确定度导致的积分量计算结果的不确定度,通常采用基于微扰理论的灵敏度与不确定度分析方法 (简称灵敏度法)量化.灵敏度分析法原则上只适用于线性模型,且一般输运计算程序难以直接进行灵敏度分析.而抽样法直接抽样核数据输入中子学计算程序进行计算,通过对计算结果的统计分析评估计算量的不确定度.抽样法易于实现、计算精确、且适用性强.在灵敏度分析与不确定度量化程序SURE中,增加了抽样法不确定度的量化功能.为将抽样法不确定度量化应用于复杂问题的模拟计算,需对其进行细致的考核.为此,选取简单的临界基准实验模型,分别采用灵敏度分析法和抽样法进行不确定度量化,得到了各核素各反应道核数据导致的k_(eff)计算不确定度.对比显示,两种方法的不确定度计算结果有很好的符合,验证了SURE程序抽样法功能的正确性.抽样法计算的k_(eff)符合正态分布,说明在一般核数据的不确定度范围内,k_(eff)与核数据近似成线性关系,利用灵敏度分析法评估k_(eff)计算值的不确定度是适用的.