Determination of pharmaceutically related compounds by suppressed ion chromatography: I. Effects of organic solvent on suppressor performance

This overall study aims to investigate gradient elution ion-exchange chromatography of pharmaceutically relevant compounds using universal nebulisation detectors, such as evaporative light scattering detection (ELSD). Addition of organic solvents to the eluent is necessary to minimise hydrophobic adsorption on the polymeric stationary phase and improve solubility of analytes. It is also necessary to de-salt the eluent prior to detection, and in this work, ion chromatography suppressors were used for this step. Such suppressors have been designed for aqueous eluents, so the purpose of the present study was to investigate the effects of methanol and acetonitrile on suppressor performance. Chemical and electrolytic suppressors were evaluated for baseline drift, noise and efficiency of suppression using aqueous/organic eluents containing up to 40% (v/v) methanol or acetonitrile. Chemical suppression of aqueous/organic eluents showed minimal noise levels, uniform low baseline and low gradient drift. Electrolytic suppression gave good performance, but with higher baseline conductivity levels and baseline drift than chemical suppression. The elevated baseline was found not to be caused by incomplete suppression of the eluent, but was attributed to chemical reactions involving the organic solvents and facilitated by high electric currents and heat generation. It was demonstrated that suppressed ion-exchange separation using a complex KOH elution profile could be coupled with ELSD, with the suppressor effectively de-salting the eluent, producing a stable baseline. Finally, complementary separation selectivity was demonstrated using a set of pharmaceutically related organic acids separated by reversed-phase and ion-exchange methods.     

SDBS与HA缓蚀剂复配的实验与理论研究

通过静态失重法研究了十二烷基苯磺酸钠(SDBS)与六亚甲基四胺(HA)在盐酸溶液中对Q235钢的协同缓蚀效应, 并采用分子动力学模拟从缓蚀剂膜抑制腐蚀粒子扩散的角度对其缓蚀机理进行分析. 结果显示: SDBS和HA单独使用时, 最高缓蚀效率分别为82.82%和79.46%, 复配后最高缓蚀效率可达到92.78%; 与两种缓蚀剂单独使用时相比, SDBS与HA复配后缓蚀剂膜体系中的自由空间明显下降, 削弱了膜内缓蚀剂分子的自扩散能力, 腐蚀粒子在缓蚀剂膜携带下的被动迁移也随之减弱; SDBS与HA复配能更有效抑制腐蚀粒子在缓蚀剂膜中的扩散, 也就是说复配后的缓蚀剂具有更好的缓蚀性能.     

腐蚀介质在缓蚀剂膜中扩散行为的分子动力学模拟

采用分子动力学模拟方法,从缓蚀剂膜阻碍腐蚀介质粒子(H2O、H3O+和HCO3-)向金属表面扩散的角度,研究了4种1-R1-2-十一烷基-咪唑啉缓蚀剂(R1:羧甲基(A),羟乙基(B),氨乙基(C),氢(D))抑制碳钢CO2腐蚀的缓蚀机理,并对其缓蚀性能进行了理论评价.腐蚀介质粒子在不同缓蚀剂膜中的扩散系数、粒子与膜的相互作用能以及膜的自扩散性能的计算结果表明:4种缓蚀剂均可形成稳定的缓蚀剂膜,能有效阻碍腐蚀介质粒子向金属表面的扩散,达到抑制或延缓腐蚀的目的;随亲水支链(R1)极性的增加,缓蚀剂膜对腐蚀介质粒子扩散行为的抑制能力逐渐增强;同种缓蚀剂膜对正负离子H3O+和HCO3-比对中性的H2O分子具有更强的扩散抑制能力.综合计算及分析结果,4种缓蚀剂缓蚀性能的理论评价结果为ABCD,与文献实验结果吻合.     

数码照相法测量离子交换平面光波导损耗特性

利用数码相机对离子交换平面玻璃光波导传输线进行数字成像,根据传输线上的光强分布拟合出光强传输衰减曲线,计算出波导的传输损耗.对光波导进行退火处理,研究了波导退火前后的传输损耗特性.退火后0阶模式下传输损耗由2.148 9 dB·cm-1降为0.746 0 dB·cm-1.结果表明,波导的传输损耗是随着模阶数的增加而递增,适当的退火处理明显改善了离子交换波导的质量.     

数码照相法测量离子交换平面光波导损耗特性

利用数码相机对离子交换平面玻璃光波导传输线进行数字成像,根据传输线上的光强分布拟合出光强传输衰减曲线,计算出波导的传输损耗.对光波导进行退火处理,研究了波导退火前后的传输损耗特性.退火后0阶模式下传输损耗由2.148 9 dB·cm－1降为0.746 0 dB·cm－1.结果表明,波导的传输损耗是随着模阶数的增加而递增,适当的退火处理明显改善了离子交换波导的质量.     

中强震的前兆地声

本文报道了滦县五级震前卢龙台站和昌黎台站的震前地声记录。从地声源的强度出发,作者对地声传播的可能距离作了初步分析。分析表明,地声一般不是来自震源,而是来自观测站附近的地下。从而说明彼此相距较远的观测站,其接收信号序列是不相关的。但由于震源体与震级成正比的关系,对于较大地震,我们仍可能在较大范围内和较早的时候收到前兆信息。     

On the complete cd-index of a Bruhat interval

We study the non-negativity conjecture of the complete cd-index of a Bruhat interval as defined by Billera and Brenti. For each cd-monomial M we construct a set of paths, such that if a “flip condition” is satisfied, then the number of these paths is the coefficient of the monomial M in the complete cd-index. When the monomial contains at most one d, then the condition follows from Dyer’s proof of Cellini’s conjecture. Hence the coefficients of these monomials are non-negative. We also relate the flip condition to shelling of Bruhat intervals.     

单粒子气溶胶的基质辅助激光解吸电离研究

单粒子气溶胶的基质辅助激光解吸/电离飞行时间质谱技术具有快速在线检测环境大气生物气溶胶的潜力.以a-环糊精为分析物,实验研究了吡啶羧酸、2,5-二羟基苯甲酸、芥子酸、阿魏酸四种常用基质材料的效果,考察基质与分析物的摩尔比对分析物单粒子激光质谱信号的影响.实验结果表明阿魏酸做基质时质谱命中率及分析物质谱信号峰检测效率最高,吡啶羧酸做基质时的分析物质谱信号峰激发率最高,信号峰强度最强.吡啶羧酸对分析物摩尔比为100:1时,分析物质谱信号检测效率最高.     

Weak toroidalization over non-closed fields

We prove that any dominant morphism of algebraic varieties over a field k of characteristic zero can be transformed into a toroidal (hence monomial) morphism by projective birational modifications of source and target. This was previously proved by the first and third author when k is algebraically closed. Moreover we show that certain additional requirements can be satisfied.