平面四方型混合配体配合物[Pd(γ-CH_3py)_2(mnt)_2]的合成和晶体结构

本文报道标题化合物（其中γＣＨ３ｐｙ是对甲基吡啶，ｍｎｔ＝ＣＮＣＮＳ－Ｓ－）的合成、鉴定和单晶结构。化合物晶体属三钭晶系，Ｐ１空间群，晶胞内分子数为２。分子中与Ｐｄ（Ⅱ）配位的四个原子呈平面四方形。讨论了结构与二阶、三阶非线性光学效应的关系。     

基于移动窗口-迭代遗传算法的近红外光谱波长选择方法

光谱样本数据常会受到环境噪声和其它组分的干扰，应作波长选择，以提高分析精度。近红外光谱谱区宽，搜索空间过大，难以直接采用遗传算法进行波长选择。为此本研究提出先用移动窗口偏最小二乘法（MWPLS）从宽谱区中初选出信息区间，再采用改进的迭代遗传算法（IGA）从中选出最优的信息子区间。MWPLS用移动窗口沿全谱区扫描，对信息区间的定位效果好，而IGA将顾及光谱数据的连续相关特性，运行多轮GA，并以上轮选择结果平滑处理后作为先验知识支持下轮的种群初始化。由此选出的连续相邻的波长点作为自变量，进行PLS建模，既可显著地简化模型，又保留一定的数据冗余，模型的稳健性好、分析精度高。将其用于小麦水分的近红外分析，效果良好，预测性能明显优于其它方法。     

一种新的具有双螺旋结构特征的光学活性分子方的设计、合成及其光学性质

分别从手性构型高度稳定的(R)和(S)-2,2'-二乙炔基-1,1'-联萘模板出发, 通过保护基的控制导入、偶联反应、保护基脱去以及分子间偶合成环4个步骤成功地合成了一种具有螺旋结构特征的新的光学活性分子方(Molecular square)(R,R,R,R)-1和(S,S,S,S)-1. 用MS, IR, UV-Vis, 1H和13C NMR以及元素分析等方法对目标化合物进行了结构表征. 测定并分析比较了2个目标化合物的比旋光度[α]D和圆二色性(CD)等光学性质. 在CH2Cl2溶液中, 异构体(R,R,R,R)-1和(S,S,S,S)-1的[α]25D值分别为+887.3°和-889.7°, 并且其CD谱表现出对称的镜像特征.     

Variable selection in multivariate calibration based on clustering of variable concept

Recently we have proposed a new variable selection algorithm, based on clustering of variable concept (CLoVA) in classification problem. With the same idea, this new concept has been applied to a regression problem and then the obtained results have been compared with conventional variable selection strategies for PLS. The basic idea behind the clustering of variable is that, the instrument channels are clustered into different clusters via clustering algorithms. Then, the spectral data of each cluster are subjected to PLS regression. Different real data sets (Cargill corn, Biscuit dough, ACE QSAR, Soy, and Tablet) have been used to evaluate the influence of the clustering of variables on the prediction performances of PLS. Almost in the all cases, the statistical parameter especially in prediction error shows the superiority of CLoVA-PLS respect to other variable selection strategies. Finally the synergy clustering of variable (sCLoVA-PLS), which is used the combination of cluster, has been proposed as an efficient and modification of CLoVA algorithm. The obtained statistical parameter indicates that variable clustering can split useful part from redundant ones, and then based on informative cluster; stable model can be reached.     

城市轨道交通客流量预测的信度模型及其应用

信度估计是产生于风险管理和精算领域的一种现代预测方法.借助信度估计的技术和方法,对城市轨道交通客流量进行短期预测.为了考虑不同车站客流量间的相依关系,建立了轨道交通客流量的多维信度预测模型.并采用天津地铁一号线的数据,对所述预测方法进行验证.     

Simultaneous,Selective and Highly Sensitive Voltammetric Determination of Lead,Cadmium, and Zinc via Modified Pencil Graphite Electrodes

Pencil graphite electrode (PGE) modified with MWCNT and Bi³⁺ (MWCNT/Bi/PGE) was utilized in simultaneous analysis of Pb²⁺, Cd²⁺, and Zn²⁺. Surface and electrochemical characteristics of MWCNT/Bi/PGE were investigated via SEM, cyclic voltammetry, electrochemical impedance spectroscopy, and FTIR measurements. Even though modification with MWCNT did not improve the electroactive surface area, it significantly decreased the charge transfer resistance. Furthermore, modification with Bi³⁺ significantly increased the sensitivity. Finally, MWCNT/Bi/PGE exhibited the highest sensitivity and reproducibility compared to PGE and PGE modified with only MWCNT. MWCNT/Bi/PGE provided LOD values of 0.27, 0.43, and 1.63 μg L⁻¹, and linear ranges of 1–80, 5–80, and 10–80 μg L⁻¹ for Pb²⁺, Cd²⁺, and Zn²⁺, respectively. Proposed modification method offers effective electroanalytical performance with low time consumption and cost for the analyst.     

On the hydrolysis mechanisms of amides and peptides

Here the possibility is raised that peptide hydrolysis, in the absence of catalysis by proteases or buffers, may still have a self‐catalyzing mechanism that differs from ordinary amide hydrolysis. Second, an attempt is made to clarify the ongoing confusion in the computational chemistry literature regarding the rate‐limiting step in ordinary amide hydrolysis. Third, Gibbs activation energies (free‐energy barriers) for formamide hydrolysis are derived from rate constants and presented under different concentration conventions, for ease of comparison to values from computational chemistry predictions past and future.     

Nafion® Coated Electropolymerised Flavanone-based pH Sensor

This work summarizes the electrochemical response of flavanone carbon composite electrodes in comparison with Nafion®-coated flavanone carbon composite electrodes, for use as voltammetric pH sensors in both buffered and low-buffered media. Square wave voltammetric measurements suggest the peak potential achieved from the electrochemical polymerization after the electron-proton oxidation responds with accuracy to buffered pH solutions for both coated and non-coated electrodes, with a potential shift of 55.1 mV and 54.6 mV per pH unit respectively. However, a considerable improvement in stability, accuracy and sensitivity is provided by the proton-transfer Nafion® layer in CO₂ bubbled sea water. Furthermore, Nafion®-coated flavanone carbon composite electrodes predicted a pH of 8.04 for the commercial seawater, which is in excellent agreement with the measured pH 8.05 value.     

Classification of categories with matrices of coefficient 2 and order n

In this paper, we present the categories associated to the square matrix with coefficients 2 of order 3. The family of categories associated to these matrices has five isomorphism classes. In the case of a matrix of order higher than 3, we only demonstrate upper and lower bounds for the number of associated categories.     

Squeezing Dynamics for One-Dimensional Infinite Square Well with a Mobile Wall

We show that the dynamics for a particle confined in one-dimensional infinite square well with a mobile boundary can be converted to the case as if the boundary is time-independent at the expense of an appropriate time-dependent Hamiltonian. The Hamiltonian is deduced by the technique of integration within an ordered product of operators.