人工神经网络及其在分析化学中的应用

人工神经网络是一种新兴的计算方法，有着广阔的发展前途，目前在分析化学领域已经有了多方面的应用。本文简要介绍了人工神经网络的原理及其在分析化学中的应用。     

电化学斑图中空间耦合的时空动力学

斑图是在空间或时间上具有某种规律性的非均匀宏观结构,普遍存在于自然界,事实上大多数电化学体系在适当参数范围内也可以形成各种电化学斑图。本文介绍了电化学斑图中空间耦合的三种方式,重点总结了在不同机理作用下可能出现的斑图种类,并简述了电化学斑图模拟方面的发展。     

一个新颖三维配位聚合物Pb(1，4-napdc)(DMF)的合成、结构及热稳定性研究

A novel 3D metal-organic coordination polymer Pb(1,4-napdc)(DMF) (1,4-napdc=naphthalene-1,4-dicarboxylate) was synthesized at room temperature using slow vapor diffusion method to grow single crystal that has been analyzed by X-ray diffraction. The crystal belongs to orthorhombic with space group P2₁2₁2₁. The unit cell parameters are as fellows: a=0.701 3(2) nm, b=1.407 6(3) nm, c=1.521 5(4) nm, V=1.501 8(6) nm³ and Z=4. In the crystal structure of Pb(1,4-napdc)(DMF), the square grids constructed with paddle-wheel units of Pb(Ⅱ) and 1,4-napdc links stack over each other to generate infinite 3D network, which has square apertures (1.158×1.158 nm²) along the crystallographic a-axis. The thermal stability of compound was investigated by differential scanning calorimetry and thermogravimetric analysis. CCDC: 293617.     

Study on pyrolysis kinetics of walnut shell

Slow pyrolysis of walnut shell which is a cheap and abundantly available solid waste was carried out using thermogravimetric analysis. The effects of raw material heating rate on the pyrolysis properties and kinetic parameters were investigated. A two-step consecutive reaction model were used to simulate the pyrolysis process. The kinetic parameters were established by using the pattern search method. Comparison between experimental data and the model prediction indicated that the two-step consecutive reaction model can better describe the slow pyrolysis of walnut shell as the formation of an intermediate during the pyrolysis process was taken into account.     

中药材巴戟天及其水煎液微量元素的分布模式

模拟传统煎药方式,制备巴戟天水煎液。用电感耦合等离子体质谱法(ICP-MS)测定了药材及其水煎液中11种微量元素Cr、Mn、Co、Ni、Cu、Zn、As、Se、Cd、Sn、Pb含量,用火焰原子吸收光谱法(FAAS)测定了微量元素Fe含量。根据微量元素含量,得到了药材及水煎液微量元素的分布模式。结果表明,巴戟天药材样品富含人体必需元素Fe、Mn、Zn,含量分别是1086.3、393.8、15.1μg.g-1;巴戟天药材与水煎液微量元素的分布模式图清晰地显示了其微量元素的分布特征,且药材与水煎液微量元素的分布模式以及不同煎制时间下水煎液微量元素的分布模式均存在明显差异,进而表明这种微量元素分布模式对中药微量元素的研究和临床应用具有参考价值。     

Short Te …︁ Te bonding contacts in a new layered ternary telluride: Synthesis and crystal structure of 2D Nb3GexTe6 (x ≃ 0.9)

The new layered ternary compound Nb₃Ge_xTe₆ (x ? 0.90) was prepared by direct combination of the elements taken in the stoichiometric proportions 3 : 1 : 6, heated at 1 000 °C for 10 days in silica tubes and quenched to room temperature. The phase crystallizes in the orthorhombic symmetry, space group Pnma (#62), with the following single crystal refined parameters: a = 643.18(5) pm, b = 1391.98(11)pm and c = 1 154.07(5) pm, with Z = 4. The structure was refined to an R of 3.4% (R_w = 4.6%), with 1969 independent reflexions and 49 parameters. The structure is based on the close stacking of trigonal prismatic (TP) slabs in the AA/BB mode. The slabs can be seen as built up from face sharing biprisms, which are filled either by one or by two niobium cations situated in the middle of the trigonal prisms. The germanium is located in the middle of the common face of two prisms, leading to a rather unusual anionic square coordination. The refinements showed that this latter cation does not fill completely its square site. No cation was found in the van der Waals gap between the slabs. The mean d_{Ge? Te} distance (276.5 pm) is in agreement with Ge^II cations, while some Te …? Te distances (from 333.84 to 361.65pm) are too short for anions in a simple contact. These bonding distances, already mentionned in some MTe₂ compounds, are to be ascribed to charge transfer in the structure, with a partial oxidation state for the tellurium anions. Short Nb? Nb and Nb? Ge distances (292.0 and 281.3 pm, respectively) imply intercationic bonding within the slabs.     

Partial least-squares regression and fuzzy clustering — A joint approach

Chemical and physical analyses of malt, the main ingredient of beer, have been used to predict the concentration of certain volatile compounds in the finished beer.The prediction was done by means of the partial least squares regression (PLS2) in SIMCA. The total data set as well as individual malt clusters were submitted to PLS analysis. Best prediction was obtained by separating the total object matrix in classes according to similarity found by fuzzy pattern recognition (FCV). FCV was also used to separate the beer variables in classes and to select the subset of variables to be predicted.A joint approach of fuzzy pattern recognition to identify groups of samples and SIMCA-PLS2 to predict several dependent variables is suggested as a powerful tool in process-analytical chemistry.     

Structure inhomogeneities of medium-range order in fluorozirconate glasses

Images of cleaved surfaces were obtained for 53ZrF₄-20BaF₂-4LaF₃-3AlF₃-20NaF (ZBLAN) glasses and fused quartz using an NTMDT atomic force microscope. It is shown that the scatter of particle size depends on the cooling rate and is 21–48.5 Å for the cleaved surface of ZBLAN glass obtained by very fast cooling and 68–172 Å for the cleaved surface of ZBLAN after slow cooling. For cleaved fused quartz, the range is 25-18 Å.     

最小一乘稳健多元分析校正

本文论述最小一乘求解的多元分析校正算法，探讨了最小一乘较常规最小二乘法及其他隐健算法的优点。用计算机数值模拟及实际多组分光谱体系对方法进行了检验，展示了最小一乘法在分析化学计量学中实际应用的可行性。     

Elektronenlokalisierung im Grundzustand und in angeregten Zuständen Pars-Orbital-Methode, 12. Mitt

UsingGleason's theorem the pars orbital concept is developed for excited states of conjugated systems described by CI-methods. A significance index is introduced to evaluate different patterns of fragmentation. The usefulness of this approach is illustrated for butadiene, biphenyl, naphthalene, and azulene.

11. Mitt.:H. Karpf, O. E. Polansky undM. Zander, Tetrahedron Lett.1978, 2069.