Direct separation of the enantiomers of reboxetine by liquid chromatography on different cellulose- and amylose-based chiral stationary phases

Summary Racemic reboxetine, (R,S)-2[(R,S)-α-(2-ethoxyphenoxybenzyl] morpholine methane sulfonate, is a mixture of the (R,R) and (S,S) enantiomers. Separation of the enantiomers of reboxetine by liquid chromatography has been investigated on three chiral stationary phases—cellulose tris-(3,5-dimethylphenylcarbamate) (Chiralcel OD), cellulose tris-(phenylcarbamate) (Chiralcel OC), and amylose tris-(3,5-dimethylphenylcarbamate) (Chiralpak AD). On these stationary phases the resolution of the (R,R) and (S,S) enantiomers was highly dependent on mobile-phase composition. When Chiralcel OD and OC were used, addition of diethylamine to the mobile phase greatly improved the separation of the enantiomers. On Chiralpak AD enantio-separation was achieved without the use of additives. Solute-mobile phase-stationary phase interactions which might participate in the mechanism of enantiorecognition are discussed.     

基于AD7791的磁通门传感器数据采集与存储系统

针对磁通门传感器检测到的多路弱磁信号,设计了一种以AD7791为采集核心的小信号采集系统,解决了六路AD采集的同步问题。以MSP430F5437超低功耗单片机为主控,运用无磁转台测试实验,实现了数据的存储和探头姿态的校正,后采用最小二乘法进行数据修正。经实验验证,该采集系统可稳定于野外长时间工作(半年以上),零点稳定度由1.7nT/h、2.4nT/h、1.4nT/h(XYZ三轴)下降到0.2nT/h、0.31nT/h、0.23nT/h,采集精度(参考地磁场49535nT)由49516nT下降到49534nT。有效的降低了系统测量误差,精度明显提高。     

固体线胀系数测定仪的改进

介绍一种新的固体线胀系数测量及温度控制方法．当温度测量精度为0．1℃时,在多个工作点上能在1．5min内保持恒温,从而消除了以往电加热方法中,由于忽略被测样品的热平衡时间而引起的误差．还自制了时间响应快的AD590M数字温度计,提高了测量精度．     

高斯分布及截断和抽样

 详细推论了高斯分布的轴对称电子束的截断方法和确定截断因子的表达式。结果表明在截断因子为0.9时,电子束发射度等于均方根发射度的二倍, 而当电子束发射度等于均方根发射度时, 截断因子仅为0.59。给出了四维坐标变量的几率密度函数公式, 并简述了相应的抽样方法。     

分析测试实验室内部质量控制中移动极差合并统计监控技术下的不确定度动态测量评估

本文采用统计质量保证技术(SQA,statistical quality rassurance)对被测体系的精密度和偏离性能做过持续性的监控分析。SQA技术的采用可以连续地表现出分析测量体系的能力,该技术的应用能确保测试数据的有效性,有利于分析测量体系潜在问题的分析。在此基础上,本文进一步提出了平均移动极差(MR)合并统计动态监控技术一本研究认为,采用该技术来进行分析测量系统的动态不确定度评估,其贡献量可由质控样品(QC)和线性拟合两部分合成。这一结论的得出能最大限度合成各种变异因素的影响,避免相关性的复杂计算,有利于分析测试实验室内部质量控制过程中测量系统的不确定度评估。     

A cohomological description of property (T) for quantum groups

We prove a Delorme-Guichardet type theorem for discrete quantum groups expressing property (T) of the quantum group in question in terms of its first cohomology groups. As an application, we show that the first L²-Betti number of a discrete property (T) quantum group vanishes.     

New Multifunctional Agents Based on Conjugates of 4-Amino-2,3-polymethylenequinoline and Butylated Hydroxytoluene for Alzheimer’s Disease Treatment

New hybrids of 4-amino-2,3-polymethylenequinoline with different sizes of the aliphatic ring linked to butylated hydroxytoluene (BHT) by enaminoalkyl (7) or aminoalkyl (8) spacers were synthesized as potential multifunctional agents for Alzheimer’s disease (AD) treatment. All compounds were potent inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with selectivity toward BChE. Lead compound 8c, 2,6-di-tert-butyl-4-{[2-(7,8,9,10- tetrahydro-6H-cyclohepta[b]quinolin-11-ylamino)-ethylimino]-methyl}-phenol exhibited an IC₅₀(AChE) = 1.90 ± 0.16 µM, IC₅₀(BChE) = 0.084 ± 0.008 µM, and 13.6 ± 1.2% propidium displacement at 20 μM. Compounds possessed low activity against carboxylesterase, indicating likely absence of clinically unwanted drug-drug interactions. Kinetics were consistent with mixed-type reversible inhibition of both cholinesterases. Docking indicated binding to catalytic and peripheral AChE sites; peripheral site binding along with propidium displacement suggest the potential of the hybrids to block AChE-induced β-amyloid aggregation, a disease-modifying effect. Compounds demonstrated high antioxidant activity in ABTS and FRAP assays as well as inhibition of luminol chemiluminescence and lipid peroxidation in mouse brain homogenates. Conjugates 8 with amine-containing spacers were better antioxidants than those with enamine spacers 7. Computational ADMET profiles for all compounds predicted good blood-brain barrier distribution (permeability), good intestinal absorption, and medium cardiac toxicity risk. Overall, based on their favorable pharmacological and ADMET profiles, conjugates 8 appear promising as candidates for AD therapeutics.     

宽量程智能射频功率检测系统研究

介绍了一种基于数字衰减器HMC274及功率-电压转换芯片AD8362的新型宽量程射频信号功率检测系统;利用微控制器STC12C5A60S2控制HMC274的衰减值,确保被测信号的功率真值在AD8362的线性转换范围内,从而使量程上限提高了31 dB;并通过GSM模块TC35i和LCD显示模块,分别实现了对功率值的远程和近程检测;经过对900 MHz射频信号的实验测试和数据拟合,功率真值量程扩大到了-50～+40 dB,输出灵敏度为50 mV/dBm。     

基于FPGA和AD768的精密程控直流信号源设计

提出了一种基于FPGA和AD768的精密可程控直流信号源实现方案。该方案通过USB2.0接口芯片接收计算机发送的信号源控制命令,以FPGA逻辑控制DAC的方式实现信号源的可程控设计,重点介绍了AD768的硬件电路设计及提高信号源精度的关键技术。实际应用表明,该信号源具有高精度、可程控和稳定性好等优点,具有很高的参考价值。     

A test to determine the nature and presence of the memory effect columns packed with the amylose tris(3,5-dimethylphenylcarbamate) stationary phase

Acid/base mobile phase modifiers affect enantioseparations in ways that are not fully understood yet, for the lack of systematic studies. This makes chiral analysis of some pharmaceuticals difficult to reproduce. Once a column has been exposed to a modifier, the selectivity of certain pairs of enantiomers may change, for the better or the worse. We study the behavior of five enantiomeric pairs, three which are highly sensitive to the addition of certain modifiers and two that have little sensitivity to these modifiers. Their use permits the determination of the extent of the memory effect response on individual columns. The selectivity of 4-chlorophenylalanine methyl and ethyl ester, and of ketoprofen improve as a solution of ethanesulfonic acid is percolated through the column. As a result, these pairs are most useful for the determination of the extent of acid memory effect on a column. The selectivity of propranolol HCl and, to a lesser degree, Tröger's base increases as a solution of diisopropylethylamine is percolated through the column. The separation of each one of these five pairs is inversely affected by the percolation of the opposite acid/base solution. We used trans-stilbene oxide (TSO) as a ‘standard’ to determine the column stability because no memory effect is observed for it (its retention, enantioselectivity, and resolution remain constant). Understanding whether a column is under the influence of the memory effect is critical to both the analysis of pharmaceutical ingredients and to the development of preparative purification techniques for racemic mixtures. Thus, columns that were unreliable for method development and method transfer, due to the memory effect and a lack of proper solvent exposure records, can now be used.