Native ethylene glycol in wine: Application of a dead volume free,very fast “deans heart-cut” system on-line with multi-chromatography

Data about the existence of native HO? CH₂? CH₂? OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C₄) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on-line with Multi-Chromatography. It was easy to produce false data by many otherwise useful single column or two-dimensional separation processes, etc.     

灰色Verhulst模型的样条插值函数的残差修正

本用样条函数对灰色Verhulst模型的残差序列进行插值拟合，然后作用于二阶线性微分方程，并以此修正原模型，得到一种新的预测模型的数值解，提高了拟合的精确度。     

A neutron polarization analysis study of Ce2Fe17 in its paramagnetic phase

Spin-flip (paramagnetic) scattering and neutron depolarization studies were performed on Ce₂Fe₁₇ in its paramagnetic phase on the Dhruva neutron polarization analysis spectrometer. The absence of normalQ dependence of the scattered spin flip intensity shows that Ce₂Fe₁₇ is not a normal paramagnetic and there exist superparamagnetic clusters of sufficiently large dimensions (～100Å). The observed neutron depolarization gives an indication of the dynamics of these Ce₂Fe₁₇ superparamagnetic clusters.     

第二类Fredholm积分方程的泰勒展开解法

本进一步发展了用Taylor公式求解第二类Fredholm积分方程的方法，并给出了近似解的误差精度分析．     

我国居民收入、人口、教育、财政政策和货币政策与居民消费模型的实证分析

本文从影响消费的各个因素:居民收入、人口、教育、国家宏观政策等着手,对各因素进行了相关分析,运用多元统计中的岭回归估计法建立消费模型。从定量和定性分析的角度,分析了我国居民消费水平、居民收入、人口增长率、各层次教育、国家财政支出和银行利率等相关因素之间相互影响的数量变动关系和内在规律,就如何提高居民消费水平促进经济协调发展提出若干对策。     

基于小波包分析及支持向量机的超音速目标识别方法研究

提出了基于小波包分析及支持向量机的超音速目标识别方法 .通过 5 .5 6mm ,7.6 2mm和 12 .7mm三种枪弹试验获取信号 ,用小波包分解激波信号 ,统计每个频带的能量特征 ,用支持向量机方法训练测试样本 ,获得了很好的分类效果 .仿真结果表明基于超音速飞行体产生的激波信号来识别目标是可行的 .     

振动系统的模态分析实验设计

利用模态分析原理和简单试验仪器，得到了直观的悬臂梁和圆盘前4阶模态振型，使学生熟悉了模态分析原理和测试方法，有利于学生对振动规律的理解．     

Synthesis and characterization of poly(vinyl alcohol)‐graft‐[poly(D,L‐lactide)/poly(D,L‐lactide‐co‐glycolide)] hydrogels

Poly(D ,L ‐lactide) and poly(D ,L ‐lactide‐co‐glycolide) with various composition and with one methacrylate and one carboxylate end group were synthesized and grafted onto poly(vinyl alcohol) (PVA) via the carboxylate group. The graft copolymers were crosslinked via the methacrylate groups using a free radical initiator. The polymer networks were characterized by means of NMR and studied qualitatively by means of IR spectroscopy. The influence of the glycolide content in the polyester grafts and of the number of ester units in the grafts on thermal properties and swellability were studied as well. The high swellability in water is characteristic of all hydrogels. Differential scanning calorimetry (DSC) showed a single glass transition temperature that occurs in the range between 51 and 69 °C. Thermogravimetric analysis (TGA) of the networks showed the main loss in weight in the temperature range between 290 and 370 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4536–4544, 2007     

Liquid Chromatography-Mass Spectrometry Determination of Six 5-Nitroimidazoles in Animal Feedstuff

A liquid chromatography-mass spectrometry method for the determination of the coccidiostats metronidazole, ronidazole, dimetridazole, secnidazole, tinidazole and ipronidazole in feedstuff was developed. The 5-nitroimidazoles were extracted from animal feed with a pH 2 phosphate buffer solution followed by a solid phase extraction procedure based on HLB cartridges. The liquid chromatographic separation of the extracts was performed on a C₁₈ bonded silica column applying a gradient of elution with pH 4.3 ammonium acetate buffer solution and acetonitrile. Quantification for each 5-nitroimidazole was carried out monitoring its molecular ion [M + H]⁺ obtained by positive electrospray ionisation mode. A pool of feedstuffs was used to optimise and validate the method. Linearity, quantification limit, intra-day and inter-day reproducibility and accuracy were estimated using this pool of feedstuffs spiked with the drugs. For the confirmatory assay, several fragment ions from each 5-nitroimidazole were obtained and monitored. The method was applied successfully to determine 5-nitroimidazoles in feedstuff at level of 0.05 mg kg⁻¹.