Determination of enantiomeric composition of samples by multivariate regression modeling of spectral data obtained with cyclodextrin guest-host complexes-Effect of an achiral surfactant and use of mixed cyclodextrins

The determination of the enantiomeric composition of samples by chemometric modeling of spectral data was investigated for samples of N,N′-bis-(-methylbenzyl) sulfamide and tryptophan methyl ester hydrochloride. Multivariate regression models (PLS-1) were developed from spectral data obtained on solutions containing N,N′-bis-(-methylbenzyl)sulfamide or tryptophan methyl ester hydrochloride in the presence of sodium dodecyl sulfate and mixed cyclodextrin host molecules. The regression models were subsequently used to predict the enantiomeric composition of laboratory-prepared test samples of N,N′-bis(-methylbenzyl)sulfamide or tryptophan methyl ester hydrochloride. The capability of the models to accurately predict the enantiomeric composition was evaluated in terms of the root-mean-square percent relative error (RMS %R.E.) as calculated from the results obtained with independently prepared validation sets of samples. It was found that the presence of SDS in most cases either had little effect on the predictive ability of the model or it actually reduced the predictive ability of the model. Moreover, it was found that the use of mixed CDs, either in the presence or absence of SDS, reduced the predictive ability of the regression model when compared with results obtained with individual CDs.     

SULFATION OF PACHYMAN WITH CHLOROSULFONIC ACID USING THE IMPROVED WOLFROM METHOD

High purity polysaccharide of pachyman was isolated from the powder of Poria cocos sclerotium with an yield of 77.8%. The intrinsic viscosity of polysaccharide was found to be 78.95 mL/g in DMSO solution at 25℃. The isolated polysaccharide was reacted with chlorosulfonic acid to obtain pachyman sulfate using the improved Wolfrom method. The results of the orthogonality experiment on the sulfation reaction identified that the effectiveness of the reaction conditions on the degree of sulfation and the value of intrinsic viscosity is in the following order: molar ratio of chlorosulfonic acid to glucoside (3-5) ＞ reaction temperature (60-80℃) ＞ reaction time (1-2 h). The kinetic studies of the pachyman sulfationindicated that the hydrolysis is accompanied with the sulfation process. The decrease in intrinsic viscosity of the sulfated pachyman is proportional to the increase in the degree of sulfation under the mild reaction conditions of ＜ 80℃,chlorosulfonic acid/glucoside mole ratio ＜ 5, and reaction time ＜ 2 h. Beyond the above reaction conditions, excessive loss of -OH group occurs during hydrolysis. The NMR results indicated a complete sulfation on C-6 and a partial sulfation on the C-2 and C-4 of glucoside.     

刚柔组合桩复合地基加固设计与应用

利用柔性桩减少刚性桩与土之间的刚度差,使之与土结合良好,达到提高复合地基承载力特征值和柔性桩软土地基加固的置换率、减少刚性桩复合地基变形及降低软地基处理造价等目的.将水泥土柔性短桩中心用沉管桩的工法施工低强度（C10）砼桩——＂刚柔组合桩＂的复合地基,处理宁波北仑某仓库的软土地基,经检测、计算验证和经济型比较,表明刚柔组合桩复合地基法可应用于软土地基工程,且能降低造价.     

丙烯酰胺与二甲基二烯丙基氯化铵共聚动力学

采用膨胀计法研究了以过硫酸铵 亚硫酸氢钠为引发剂,丙烯酰胺（AM）和二甲基二烯丙基氯化铵（DMDAAC）在水溶液中的共聚反应动力学,测定了相应的聚合表观活化能、聚合速率方程和单体竞聚率。 结果表明,当AM与DMDAAC摩尔比分别为5∶5、6∶4和7∶3时,表观活化能分别为Ea1=90.61 kJ/mol、Ea2=88.88 kJ/mol和Ea3=85.15 kJ/mol;聚合反应温度为45 ℃下,聚合速率方程分别为Rp1=kc(M)2.84c(IO)0.51·c(IR)0.61,Rp2=kc(M)2.77c(IO)0.51c(IR)0.59和Rp3=kc(M)2.73c(IO)0.50c(IR)0.56;2种单体的竞聚率分别为rAM=6.11,rDMDAAC=0.14。 上述实验结果可从动力学角度为不同阳离子度共聚物Poly(DMDAAC-co-AM)（PDA）聚合反应速率差别及产物特征黏度值差异进行解释。     

铜纳米薄片双轴应变弹性响应的第一性原理研究

近年来,在纳米尺度的研究中应用到很多表面的技术和概念.然而,以往针对表面的研究中对象为单晶块体样品,这些研究结果将不再适用纳米材料.为了研究表面对纳米体系弹性响应的影响,选取较为简单的铜纳米薄片为研究对象,构建了铜（111）面和（001）面的薄片模型,使用第一性原理方法计算了铜纳米薄片的双轴泊松比,分析了纳米薄片与体材料的差异,研究不同厚度纳米薄片中表面对内层原子的影响.计算结果显示,表面原子层的双轴泊松比大于内部原子层,并且其收敛速度和数值大小均和薄片取向有关.根据双轴泊松比随厚度的变化特性,可以得到不同取向的纳米薄片中表面对弹性响应的临界厚度.     

Stochastic resonance for a metapopulation system driven by multiplicative and additive colored noises

We investigate the stochastic resonance(SR) phenomenon induced by the periodic signal in a metapopulation system with colored noises. The analytical expression of signal-to-noise is derived in the adiabatic limit. By numerical calculation, the effects of the addictive noise intensity, the multiplicative noise intensity and two noise self-correlation times on SNR are respectively discussed. It shows that:(i) in the case that the addictive noise intensity M takes a small value, a SR phenomenon for the curve of SNR appears; however, when M takes a large value, SNR turns into a monotonic function on the multiplicative noise intensity Q.(ii) The resonance peaks in the plots of the multiplicative noise intensity Q versus its self-correlation time τ1 and the addictive noise intensity M versus its self-correlation time τ2 translate in parallel. Meanwhile, a parallel translation also appears in the plots of τ1 versus Q and τ2 versus M.(iii) The interactive effects between self-correlation times τ1 and τ2 are opposite.     

比值导数法矿物组分光谱解混模型研究

矿物丰度含量的精确分析是高光谱遥感技术定量分析中的难点。将化学领域的比值导数光谱算法进行总结,将其引入遥感反射率光谱分析,提出了基于线性光谱混合模型的比值导数光谱解混模型,并利用石膏和绿帘石粉末混合物进行了模型的精度分析。实验结果表明,矿物粉末混合物在不同波段其光谱混合特性有所不同,其中部分波段有较强的线性混合特征。采用部分强线性混合波段进行光谱解混,可以取得比全波段解混算法更好的结果。比值导数法光谱解混模型简洁,可以得到高精度的矿物成分反演结果,对于固定端元组成的混合光谱定量分析有较大潜力。     

一种可拆装式的脑外科手术用磁共振成像线圈

在临床磁共振成像(MRI)应用中,射频线圈的设计是非常关键的,针对不同的应用目的,合适的线圈能获得质量更好的图像. 有的应用需要线圈提供均匀性较好的射频场,而有的应用则需要线圈在特定区域内提供高的信噪比(SNR). 但是线圈很难同时得到好的射频场（B₁场）、空间均匀性和高的SNR,需要根据实际应用情况进行折衷设计. 针对MRI在脑外科手术中的应用特点,设计并制作了一种新颖的、适用于脑外科手术的MRI接收和发射共用射频线圈. 该线圈采用可分拆式结构,在脑外科手术支架上可以进行反复组装和拆卸,减少了MRI对医生手术的影响. 仿真结果和人体成像实验表明,该线圈能产生均匀的射频场、有较高的SNR和较大的成像范围,满足脑外科手术的需要.     

弹光调制光电转换放大电路设计

弹光调制干涉具调制的干涉光被探测器接收后输出高速变化的微弱电信号,能否将该电信号提取并放大输出对弹光调制-傅里叶变换光谱仪的研制至关重要。通过对调制干涉光进行理论分析,设计一种具有高信噪比和较高带宽的光电转换放大电路,主要由电源电路、光电转换电路、放大电路、理论通频带为100 kHz~3.5 MHz的带通滤波电路组成。实验结果表明:设计的电路能够将探测器输出的最大频率为1.6 MHz的信号放大至670 mV左右,实现了将探测器输出的微弱速变电信号从背景噪声中有效提取与放大,为后续傅里叶变换提供可靠数据。     

基于数字图像处理技术的树脂眼镜镜片缺陷检测研究

通过设计的镜片自动检测光学硬件系统,给出了树脂镜片精细杂质图像处理措施,将图像差分法应用于镜片图像边缘的去除;同时解决了镜片检测灰尘影响的问题;另外运用改进型的归一法解决杂质计数问题,为自动化分级分拣系统的研发提供重要的数据支持,为镜片缺陷检测系统的后续分级分拣的数字控制模块提供了可操作性。该检测系统检测精度为0.03 mm、速度为1片/s,检测误差控制在5%。