Recent developments in electrochemical detection of cadmium

Heavy metal cadmium (Cd) poses extreme toxicity to the environmental and human health, thus its detection provides a great challenge in the environmental and analytical science, yet the solution is needed urgently owing to the adverse effects. During the past years, the electrochemical techniques have received considerable attentions for Cd²⁺ determination due to their unique advantages. In this review, a common introduction was provided firstly and followed by the detection principles. Then, a fully comprehensive elucidation of the recent developments in electrochemical detection of Cd²⁺ was presented. Finally, the critical challenge and perspectives of Cd²⁺ detection were outlined.     

Long-chain double SO3H-functionalized Brønsted acidic ionic liquids catalyzed selective alkylation of phenol and p-cresol with tert-butanol

A simple, efficient, and selective approach for the tert-butylation of phenol and p-cresol using two double SO₃H-functionalized long-chain Brønsted acidic ionic liquids as recyclable catalysts is reported. Under optimum reaction conditions, 89.4% conversion of the phenol and 73.7% selectivity of 2,4-tert-butyl-phenol and 93.2% conversion of the p-cresol and 89.2% selectivity of 2-tert-butyl-p-cresol were obtained. Two ionic liquids could be recovered readily and their catalytic activity almost completely retained after five recycles.     

研究报告(191~196)基于微波技术的翻白草多糖提取工艺研究

采用醇沉水提工艺,使用微波技术提取翻白草中多糖.先通过单因素分析法对提取工艺进行优选,并选取4个因素进行正交实验.得到翻白草中多糖的最优提取工艺为:先使用料液比为1∶30的乙醇进行醇沉20 min,再以液固比为70∶1的水(p H为7.0)作为提取剂,在60℃下微波提取10 min.在最优提取工艺下对翻白草不同部位(根、茎、叶)的多糖含量进行分析,发现翻白草的茎部多糖的含量最高,其次为根部和叶部.     

一道数学考研试题的解答

对复旦大学的一道研究生入学考试题给出了八种解法.     

地沟油特异性指标研究

精炼地沟油相比于食用植物油,经历了更长时间的高于200 ℃的高温历程,第三类地沟油或称煎炸老油也经历了长时间高温历程。本文应用ATR红外光谱法,研究了六种常用植物油中共轭脂肪酸甘油酯含量、反式脂肪酸甘油酯含量、不饱和度等三个指标值随加热温度及加热时间的变化情况,以期找出地沟油的特异性指标。研究结果表明: 从160 ℃开始,各植物油的共轭脂肪酸甘油酯含量及反式脂肪酸甘油酯含量随着加热温度升高及加热时间增长而增加,不饱和度则降低,当加热温度为200 ℃或以上、加热时间达到4 h或更长时,六种植物油的三个指标值有大幅变化。共轭脂肪酸甘油酯含量的变化幅度还与植物油中亚油酸含量有关,亚油酸含量越大其变化幅度越大;反式脂肪酸甘油酯含量变化幅度则还与植物油中油酸含量有关,油酸含量高者变化幅度大。此外,上述三个指标值与存储时间有关,随着六种植物油存放时间增长,共轭脂肪酸含量变大,不饱和度变小,而反式脂肪酸含量变化规律与高温长时间加热不同,其含量不是变大而是变小,保质期内三个指标值的变化幅度都小于经过高温长时间加热的变化幅度。因此,从三个指标值及其变化规律可以了解植物油是否经历了长时间高温历程,它们可以作为地沟油及精炼地沟油的特异性指标。     

Preparation and Properties of HBS Lignin from Masson Pine

In order to establish a new method for making cellulose and lignin from Masson pine, a high boiling solvent (HBS) pulping process with an aqueous solvent of 1,4-butanediol was investigated. Masson pine chips were pulped with a 70%--90% aqueous solution of 1,4-butanediol containing a small amount of a catalyst at 200--220℃ for 60--180 min. HBS Masson pine cellulose is suitable for making paper. Water-insoluble HBS lignin was separated from the liquor reaction mixture by water precipitation. The recovered high boiling solvent (RHBS) is able to be recycled as a pulping solvent, indicating that the HBS method is a pulping process of Masson pine which is energy saving, resources saving and pollution free. HBS lignin has a better chemical reactivity and a lower ash content than lignin sulfonate.     

自适应memetic算法求解集合覆盖问题

集合覆盖问题是一个经典的NP困难的组合优化问题,有着广泛的应用背景.首先,采用动态罚函数法将集合覆盖问题等价转化为无约束的0-1规划问题.然后,基于集合覆盖问题的结构特征,设计了初始种群构造方法、局部搜索方法、交叉算子、动态变异算子和路径重连策略,提出了一个高效求解该0-1规划问题的自适应memetic算法.该算法有效平衡了集中搜索和多样化搜索.通过45个标准例子测试该算法,并将其结果与现有遗传算法进行了比较,表明该算法能够在可接受的时间内找到高质量的解,能够有效求解大规模集合覆盖问题.     

2,4,6-Tri(4-pyridyl)-1,3,5-triazine: Photoinduced Charge Separation and Photochromism in the Crystalline State

2,4,6-Tri(4-pyridyl)-1,3,5-triazine (tpt) is a widely used ligand for functional coordination compounds. In this work, tpt has shown unprecedented photochromism in the crystalline state. Experimental and theoretical data has revealed that the photocoloration of tpt very likely originates from intramolecular charge separation and the formation of a triplet diradical product. This finding demonstrates a new simple, neutral photochromic molecule and endows the tpt molecule and related compounds with potential optical applications.     

Research Progress of the Biosynthesis of Natural Bio-Antibacterial Agent Pulcherriminic Acid in Bacillus

Pulcherriminic acid is a cyclic dipeptide found mainly in Bacillus and yeast. Due to the ability of pulcherriminic acid to chelate Fe³⁺ to produce reddish brown pulcherrimin, microorganisms capable of synthesizing pulcherriminic acid compete with other microorganisms for environmental iron ions to achieve bacteriostatic effects. Therefore, studying the biosynthetic pathway and their enzymatic catalysis, gene regulation in the process of synthesis of pulcherriminic acid in Bacillus can facilitate the industrial production, and promote the wide application in food, agriculture and medicine industries. After initially discussing, this review summarizes current research on the synthesis of pulcherriminic acid by Bacillus, which includes the crystallization of key enzymes, molecular catalytic mechanisms, regulation of synthetic pathways, and methods to improve efficiency in synthesizing pulcherriminic acid and its precursors. Finally, possible applications of pulcherriminic acid in the fermented food, such as Chinese Baijiu, applying combinatorial biosynthesis will be summarized.