One-pot three-component synthesis of tetrahydrobenzo[b]pyrans catalyzed by cost-effective ionic liquid in aqueous medium☆

A simple and efficient method is proposed for the synthesis of tetrahydrobenzo[b]pyrans with aromatic alde-hydes, active methylene compounds, and dimedone using basic ionic liquid catalyst in water. The procedure offers several advantages including short reaction time, good yield, easy procedure, and good recyclability of catalysts, which may be a practical alternative to conventional processes for preparation of 4-hpyrans.     

数据关联的粒化树描述方法

为探讨数据关联问题,对数据集实施分层粒化处理,得到分层结构的粒化树.进而利用粒化树的层次信息和粒度的数值表示,并通过关联数据产生的数据联系,给出两棵粒化树之间数据关联的定义.文中视上近似为算子,借助上近似运算对应的粒,获得数据关联的判定定理,并基于粒度的数值信息判定关联紧密程度,形成数据关联的粒化树描述方法,其展示的粒化分层和粒度数值表示可看作粒计算研究的一种形式.实例的讨论表明粒化树方法的应用价值     

加权交叉验证神经网络在水质预测中的应用

在之前的研究中使用人工神经网络进行水质指标预测已经取得一定效果,在此基础上将交叉验证应用于人工神经网络的训练,获得更加准确的预测结果。以澧水某监测站的水质实测数据作为样本,选取总磷、总氮、溶解氧等6个指标,建立水质预测模型。在运用Levenberg-Marquardt优化算法对学习样本进行优化的基础上,采用加权的k-fold交叉验证方法来构建神经网络集合,构建集合时采取三种不同的混合方式：平均值、中间值和加权累积。针对不同的指标,进行了一系列的实验,总的来说,新的预测方法与简单0倍验证相比有更好的预测结果,在所有指标中氨氮和溶解氧含量预测准确率比其他指标高。     

高压水射流清洗对基体去污效果及损伤的研究

利用高压水射流清洗技术对涂层及不同硬度工件进行冲击试验,利用白光干涉仪测定试验前后工件的涂层去除情况及表面粗糙度变化情况,并观察工件受冲击后表面产生的损伤微观形貌。结果表明,利用高压水射流清洗涂层时,选择具有涂层开放表面处入射可以快速使开放面扩张,涂层去除速度会呈直线增大;工件表面质量变化与初始表面质量无关,仅受水射流冲击环境影响;水射流冲击造成工件表面损伤,产生特殊形状孔洞,此种孔洞中部高度平缓,从中心沿径向向外逐步凹陷-突起-凹陷。     

基于特征脂肪酸的掺伪芝麻油快速鉴别模型建立

脂肪酸是植物油中的主要营养成分,不同种类的食用油中所含的脂肪酸含量也不相同,本研究据此对芝麻油掺入大豆油、花生油、棉籽油的油样应用近红外光谱技术建立测定4 种脂肪酸含量的方法。以气相色谱法测定的脂肪酸含量作为化学值,校正集样品数为122,验证集样品数为38,结果表明：掺假芝麻油油样的亚麻酸
（C18∶3）、花生酸（C20∶0）、木焦油酸（C24∶0）和肉豆蔻酸（C14∶0）对近红外有特异吸收。分别建立4 种脂肪酸含量的模型,通过对模型进行优化,校正集样品的化学值与近红外的预测值的相关系数（R2）分别为R2（C18∶3）=0.989、R2（C20∶0）=0.995、R2（C24∶0）=0.993、R2（C14∶0）=0.996。验证集样品的化学值与近红外的预测值的R2分别为0.984、0.949、0.956、0.988。4 种脂肪酸含量的预测平均相对误差依次为6.0%、5.6%、4.4%、4.8%。     

食品安全与食品技术壁垒

论述日本、美国、韩国等进口国以及欧盟采取各种食品技术壁垒对我国食品出口造成的影响,并通过对我国食品安全现状及所存在主要问题的分析,总结出解决我国食品安全问题和突破食品技术壁垒的具体措施,指明未来我国食品安全的研究方向.     

牛奶中大肠杆菌和无乳链球菌的快速检测

大肠杆菌和无乳链球菌是两种导致奶牛乳房炎的重要致病菌,这两种致病菌的检测有助于及时诊断和治疗奶牛乳房炎,从而有效控制牛奶质量.利用16S-23S rDNA间区作为检测靶点,建立牛奶中大肠杆菌和无乳链球菌的快速PCR检测方法,并对该检测方法的灵敏度和特异性进行了确认.结果显示,该方法对于牛奶中大肠杆菌和无乳链球菌的检出限均能够达到1 cfu/mL,并且与其它7种对照菌株均无交叉反应,整个检测过程可在20 h内完成.     

Study on biological activities of Physalis alkekengi var. francheti polysaccharide

BACKGROUND: Physalis alkekengi var. francheti is a well‐known edible and medicinal plant in oriental countries. Recent reports indicate that polysaccharides play an important role as a dietary free radical scavenger for the prevention of oxidative damage. RESULTS: Antioxidant studies showed that fruit polysaccharide (FP) had higher scavenging effects on 1,1‐dipheny‐l‐2‐picrylhydrazyl, hydroxyl radical assay (·OH) than vitamin C and fruit calyx polysaccharide (FCP) in vitro. The results of animal experiments showed that D ‐galactose‐induced aging in mice, as evidenced by alterations in superoxide dismutase, glutathione peroxidase, catalase and monoamine oxidase activities and malondialdehyde level, was ameliorated by FP treatment. Moreover, FP could distinctly prolong the loaded‐swimming time of mice, lower the content of blood urea nitrogen of post‐exercise mice, decrease the consumption of liver glycogen and increase the activity of lactic dehydrogenase. All these results suggested that FP functioned in resisting the production of fatigue and accelerating the dispelling of fatigue. CONCLUSION: The present study suggests that Physalis alkekengi var. francheti would be a valuable source of polysaccharide and FP is able to effectively scavenge free radicals, delay aging in mice and resist the production of fatigue. Copyright © 2009 Society of Chemical Industry     

Development of a chemiluminescent enzyme‐linked immunosorbent assay for five sulfonamide residues in chicken muscle and pig muscle

BACKGROUND: An enzyme‐linked immunosorbent assay (ELISA) based on polyclonal antibodies with enhanced chemiluminescent (ECL) detection of sulfonamides in food samples has been optimised and characterised. The specificity of the assay was assessed by determining cross‐reactivities with a set of 16 sulfonamides. The aim of this study was to develop a method for determining sulfonamides with high sensitivity. RESULTS: The sensitivity of the developed ECL‐ELISA was higher than that of colorimetric ELISA. The sensitivities of five of the sulfonamides (sulfisozole, sulfathiazole, sulfameter, sulfamethoxypyridazine and sulfapyridine) ranged from 0.73 to 2.92 µg L^?1, with limits of detection of 0.10–0.43 µg L^?1. The coefficients of variation of intra‐assay and inter‐assay studies carried out over 5 days were mostly less than 10%. Recovery studies of chicken muscle and pig muscle were performed with simple and rapid extraction. Good recoveries (62.1–110.3%) were achieved and the results correlated well with those obtained using high‐performance liquid chromatography analysis. CONCLUSION: This study has provided an effective analytical technique for the rapid and reliable determination of residues of sulfisozole, sulfathiazole, sulfameter, sulfamethoxypyridazine and sulfapyridine in food samples with high sensitivity. To the authors' knowledge, this is the first report on chemiluminescent ELISA for sulfonamide analysis. Copyright © 2008 Society of Chemical Industry     

用窗口卷积实现反卷积的算法研究

本文提出了一种用窗口卷积实现反卷积的新算法,这种算法解决了用圆周卷积计算反卷积时出现的病态问题.对用圆周卷积、线性卷积和窗口卷积实现反卷积三种方法进行误差、计算量与存储空间的分析和对比.结果表明,用窗口卷积实现反卷积运算的误差、计算量和存储空间都是最小的.