3-甲基环状乙撑磷酸二酯醇解的反应途径的理论研究

采用密度泛函理论和MP2方法研究了3-甲基环状乙撑磷酸二酯(MEP)与甲醇的反应途径:(Ⅰ)CH3O-+MEP;(Ⅱ)CH3OH+MEP;(Ⅲ)CH3O-+HMEP(MEP的质子化形式);(Ⅳ)CH3OH+HMEP.在B3LYP/6-31++G(d,p)水平上优化了四条反应途径的反应物、中间体、过渡态及产物的几何构型,并在同水平上进行了自然电荷分析,然后在MP2/6-311++G(3df,2p)水平上计算了各驻点的单点能.采用极化连续介质模型(PCM)研究了各途径在苯、甲醇和水溶液中的溶剂化效应.计算结果表明,溶剂效应使途径(Ⅰ)的自由能垒降低,而使途径(Ⅱ)和(Ⅳ)的决速步骤的自由能垒升高.在气相和苯溶剂中途径(Ⅳ)是反应的优势途径,在甲醇和水溶剂中途径(Ⅰ)则成为最优.研究结果进一步表明实验条件下途径(Ⅱ)与(Ⅳ)对总醇解反应的贡献相当.     

固溶体Ce0.8Pr0.2O2-δ的合成及性质研究

利用溶胶-凝胶方法合成了Ce0.8Pr0.2O2-δ固溶体, XRD结果表明,经200 ℃焙烧就已经形成立方萤石结构固溶体,晶粒尺寸为8.1 nm, 随焙烧温度的升高,晶粒尺寸增大. X射线光电子能谱(XPS)结果表明,样品中存在氧离子缺位,铈离子主要为Ce4 离子,镨离子以混合价态Pr3 和Pr4 存在. 固溶体Ce0.8Pr0.2O2-δ的拉曼谱(Raman)观察到4个峰,458和1140 cm-1峰为特征F2g振动谱带,较宽的570和187 cm-1峰对应氧离子缺位及引起的不对称振动. 交流阻抗谱表明固溶体Ce0.8Pr0.2O2-δ在600 ℃时的电导率为1.44×10-3 S·cm-1, 活化能为Ea=0.67 eV (650～800 ℃), Ea=0.91 eV (400～600 ℃).     

Discrimination of Ganoderma lucidum according to geographical origin with near infrared diffuse reflectance spectroscopy and pattern recognition techniques

A rapid and nondestructive near infrared (NIR) method combined with chemometrics was used to discriminate Ganoderma lucidum according to cultivation area. Raw, first, and second derivative NIR spectra were compared to develop a robust classification rule. The chemical properties of G. lucidum samples were also investigated to find out the difference between samples from six varied origins. It could be found that the amount of polysaccharides and triterpenoid saponins in G. lucidum samples was considerably different based on cultivation area. These differences make NIR spectroscopic method viable. Principal component analysis (PCA), discriminant partial least-squares (DPLS) and discriminant analysis (DA) were applied to classify the geographical origins of those samples. The results showed that excellent classification could be obtained after optimizing spectral pre-treatment. For the discriminating of samples from three different provinces, DPLS provided 100% correct classifications. Moreover, for samples from six different locations, the correct classifications of the calibration as well as the validation data set were 96.6% using the DA method after the SNV first derivative spectral pre-treatment. Overall, NIR diffuse reflectance spectroscopy using pattern recognition was shown to have significant potential as a rapid and accurate method for the identification of herbal medicines.     

Short-wave near-infrared spectroscopy analysis of major compounds in milk powder and wavelength assignment

In this study, short-wave near-infrared (NIR) spectroscopy at 800–1050 nm region was investigated for the analysis of main compounds in milk powder. Through quantitative analysis, the feasibility is further demonstrated for the simultaneous measurement of fat, proteins and carbohydrate in milk powder. Two models, partial least-squares and least-squares support vector machine, were compared and utilized for regression coefficients and loading weights. The affect of standard normal variate spectral pretreatment to model performance was evaluated. Based on the resulted coefficients and loading weights, interesting wavelength regions of nutrition in milk powder are screened and the assignment of all specific wavelengths is firstly proposed in the details associated with chemical base. Instead of the whole short-wave NIR spectral data, these assigned wavelengths which can be reliably exploited were used for the content determination. Compared with other spectroscopy technique, assigned short-wave NIR spectral wavelengths did a good work. Determination coefficients for prediction are 0.981, 0.984, and 0.982, respectively for three components. The proposed wavelength assignment in the short-wave NIR region could be used for the component contents determination of milk powder, and could be as a guidance to interpret the spectra of milk powder.     

AR-Ag(Ⅰ)体系的共振散射光谱法测定痕量银

在pH=4.4的NaAc-HAc缓冲介质和2.0×10-3mol/L十二烷基苯磺酸钠(SDBS)溶液中,Ag(Ⅰ)与茜素红(AR)可形成较稳定的离子缔合物微粒,其在324、360和500nm处分别产生3个较强的共振散射峰.在最佳实验条件下,浓度在0.022～2.160μg/mL之间的Ag(Ⅰ)与共振散射强度△I324nm呈较好的线性关系,检测限为0.139 ng/mL.据此,建立了一种测定痕量银的共振散射新方法,并将该方法用于废胶片中痕量银的测定.     

双β-二酮配体配位性的理论研究

基于自洽反应场(SCRF)中的极化连续介质模型(PCM), 采用密度泛函理论B3LYP/6-31G**计算了以二硫醚和芳环为桥基的两类双β-二酮配体的空间构型和电子结构, 结合其配合物晶体结构数据, 研究配体分子电子结构与配位性的关联性. 结果表明, 配体分子的几何构型、前线轨道、偶极矩和电荷布居, 与配合物构型、活性配位原子和配位形式(单核或多核、分子内或分子间)之间的关联性与一致性十分有意义. 配体的理论计算研究可以在一定层次上为配合物几何结构特征和配位特性提供合理的分析与预测.     

以苯为模块自组装合成碳纳米片

在300 ℃苯溶剂中, 以无水三氯化铝为催化剂, 以苯和六氯乙烷为碳源, 基于傅克烷基化反应生成三氯乙烯苯, 并以之为模块自组装合成了具有叠层结构的碳微米颗粒, 其层片厚度为300～500 nm. 进而在反应体系和反应条件不变的情况下, 通过引入铝粉颗粒作为基底成功地诱导出厚度为30～50 nm的碳纳米片. 实验结果表明, 所得碳材料由纳米石墨微晶和非晶碳组成. 文中探讨了叠层结构的台阶长大机制, 以及碳纳米片在铝粉表面的异质形核机制.     

The application of digital image recognition to the analysis of two-dimensional fingerprints

High-performance liquid chromatography (HPLC) fingerprint has been commonly used in the quality control and assessment of herbal medicines, and two-dimensional (2D) fingerprint obtained by means of HPLC-diode array detector (HPLC/DAD) can provide higher reliability. In this paper, an approach to the analysis of the 2D HPLC/DAD fingerprints, which was based on digital image recognition techniques, was developed for the first time. First, wavelet transform was employed to eliminate noise signal in the 2D fingerprint, and then the 2D fingerprint was converted into grayscale image. Second, several features of the image were calculated, and hierarchical clustering. This approach was applied to the qualitative analysis of the different samples of coptis chinensis, and the clustering result of samples was all highly consistent with the real situation. Based on the densities in grayscale image, three components in standard samples were quantitative analyzed, and the obtained correlation coefficients between concentration and grayscale density were more than 0.999. Our study indicated that the analysis of the 2D HPLC/DAD fingerprint was successful based on the idea and techniques of digital image recognition techniques, and this proposed approach provided a new pathway for the analysis of two-dimensional spectrums.     

Structure of aqueous sodium metaborate solutions: X-ray diffraction study

A structural analysis of aqueous sodium metaborate solutions (NaBo₂ · nH₂O, n = 10, 15, 20) at 298 ± 0.5 K by a rapid liquid ??-?? X-ray diffractometry with a highly effective X??celerator detector is reported in present paper. The radial distribution functions (RDF) and theoretical partial radial distribution functions for B-O, O-O, Na-O, Na-B, and Na-Na atom pairs were obtained from precisely diffraction data processing. Structure of aqueous sodium metaborate solutions was given through model calculation and described in three different items: hydrated sodium ion, hydrated metaborate ion and ion association. Effects of concentration on the structure of the solutions were discussed in detail. The mechanisms of ion aggregation and the formation of crystal nuclei in the solution are proposed. The results show that a clear picture of the structure of aqueous sodium metaborate solution has been acquired.     

Time and poling history dependent energy storage and discharge behaviors in poly(vinylidene fluoride-<Emphasis Type="Italic">co</Emphasis>-hexafluoropropylene) random copolymers

 We studied cycle time (0.01–10 s with triangular input waves) and poling history (continuous versus fresh poling) dependent electric energy storage and discharge behaviors in poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)] films using the electric displacement ― the electric field (D-E) hysteresis loop measurements. Since the permanent dipoles in PVDF are orientational in nature, it is generally considered that both charging and discharging processes should be time and poling history dependent. Intriguingly, our experimental results showed that the charging process depended heavily on the cycle time and the prior poling history, and thus the D-E hysteresis loops had different shapes accordingly. However, the discharged energy density did not change no matter how the D-E loop shape varied due to different measurements. This experimental result could be explained in terms of reversible and irreversible polarizations. The reversible polarization could be charged and discharged fairly quickly (< 5 ms for each process), while the irreversible polarization depended heavily on the poling time and the prior poling history. This study suggests that it is only meaningful to compare the discharged energy density for PVDF and its copolymer films when different cycle times and poling histories are used.