Density functional study of the antioxidant activity of some recently synthesized resveratrol analogues

In this paper we have investigated the two main working mechanisms (H atom and single-electron transfer) of five new potential antioxidant analogues of cis-resveratrol. The O–H bond dissociation energy (BDE) and ionization potential (IP) key parameters were computed in methanol. Results obtained indicate that all the examined compounds are more efficient antioxidants than the molecule from which they derive, mainly due to their higher degree of conjugation and the capability to delocalize the π-electrons which contribute to the stabilization of the radical species. The enhancement of these stabilizing effects is in part a result of the introduction of a single bond between the C2′ and C6 carbon atoms of cis-resveratrol that generates a new central aromatic ring. However, the number of hydroxyl groups and in particular the presence of the catechol moiety remains the most significant features in determining the order of radical scavenging potentiality. Spectroscopic UV–Vis characterization is also reported and discussed.     

BDE-LSSVM在柴油机气门故障诊断中的应用

针对柴油机气门故障的诊断样本少和非线性数据特征等问题,最小二乘法的支持向量机（LSSVM）能够较好地进行诊断研究,但由于惩罚因子[C]和内核参数[σ]的选取对诊断结果影响较大,有必要对其进行参数优化,因此提出了基于二进制微分进化算法（BDE）的最小二乘法支持向量机算法。利用柴油机气门振动信号作为数据,经小波变换作为模型特征,建立了基于BDE-LSSVM故障诊断模型,并与基于遗传和基于粒子群算法的LSSVM模型进行柴油机气门故障诊断的性能对比。比较结果证明,基于BDE优化的LSSVM模型在故障特征选取前后具有更好的适应度值和稳定度,故障分类准确性高且运算速度更快。     

A DFT study of the reactivity of OH groups in quercetin and taxifolin antioxidants: The specificity of the 3-OH site

Over the past decade, the chemical behaviour of flavonoids as antioxidants has become the subject of intense experimental research. In this paper, we use a quantum-chemical approach to shed light on the reactivity of two flavonoids, quercetin and taxifolin. We particularly focus on the 3-OH site and the role played by the 2,3-double bond in the reactivity of that site. In order to establish the most efficient theoretical methodology, different methods, either Hartree–Fock-based or derived from density functional theory, and different basis sets (from 6-311G(d) to 6-311++G(2d,p)) were tested on phenol and catechol, for which experimental bond dissociation enthalpy (BDE) values are available. It appears that (U)B3P86/6-311+G(d,p) is the most relevant method for BDE prediction of these phenolic compounds and it has, therefore, been used for an extensive study of the two flavonoids.     

房产平面图管理系统的开发

叙述了某房产平面图管理系统的开发情况，重点介绍了该系统的程序结构、工作原理及主要模块的开发情况。