The Lagrangian Globalization Method for Nonsmooth Constrained Equations

The difficulty suffered in optimization-based algorithms for the solution of nonlinear equations lies in that the traditional methods for solving the optimization problem have been mainly concerned with finding a stationary point or a local minimizer of the underlying optimization problem, which is not necessarily a solution of the equations. One method to overcome this difficulty is the Lagrangian globalization (LG for simplicity) method. This paper extends the LG method to nonsmooth equations with bound constraints. The absolute system of equations is introduced. A so-called Projected Generalized-Gradient Direction (PGGD) is constructed and proved to be a descent direction of the reformulated nonsmooth optimization problem. This projected approach keeps the feasibility of the iterates. The convergence of the new algorithm is established by specializing the PGGD. Numerical tests are given. This author's work was done when she was visiting The Hong Kong Polytechnic University. His work is also supported by the Research Grant Council of Hong Kong.     

2020 Roadmap on two-dimensional nanomaterials for environmental catalysis

This roadmap demonstrates a series of two-dimensional nanomaterials, such as graphene, black phosphorus, oxides, layered double hydroxides, chalcogenides, bismuth-based layered compounds, MXenes, metal organic frameworks, covalent organic frameworks, and others, for environmental catalysis.     

超高效液相色谱法测定饲料中苯乙醇胺A

建立了超高效液相色谱(UPLC)结合二极管阵列检测器(PDA)测定饲料中苯乙醇胺A的方法。根据样品基质的特点,采用相应提取液(配合饲料:0.1%甲酸-甲醇,浓缩饲料:0.1%甲酸-甲醇(10∶90,V/V);添加剂预混合饲料:0.1%甲酸-甲醇(20∶80,V/V)进行振荡提取,混合阳离子固相萃取柱(PCX)净化。采用Acquity UPLC BEH Shield RP18色谱柱,以0.1%甲酸溶液-甲醇为流动相进行梯度洗脱,流速为0.4 mL/min,检测波长为278 nm。本方法线性范围为0.1～100 mg/L;线性相关系数为0.999;定量限为1.0 mg/kg。不同饲料样品基质中苯乙醇胺A的回收率为68.7%～96.8%;相对标准偏差(RSD)为2.4%～7.0%。本方法简单快速,线性范围广,应用于实际样品检测,结果满意。     

Substrate-Induced Dimerization Assembly of Chiral Macrocycle Catalysts toward Cooperative Asymmetric Catalysis

An artificial system of substrate-induced dimerization assembly of chiral macrocycle catalysts enables a highly cooperative hydrogen-bonding activation network for efficient enantioselective transformation. These macrocycles contain two thiourea and two chiral diamine moieties and dimerize with sulfate to form a sandwich-like assembly. The macrocycles then adopt an extended conformation and reciprocally complement the hydrogen-bonding interaction sites. Inspired by the guest-induced dynamic assembly, these macrocycles catalyze the decarboxylative Mannich reaction of cyclic aldimines containing a sulfamate heading group. The imine substrate can be activated toward nucleophilic attack of β-ketoacid by a cooperative hydrogen-bonding network enabled by sulfamate-induced dimerization assembly of the macrocycle catalysts. Highly efficient (>95 % yield in most cases) and enantioselective (up to 97.5:2.5 er) transformation of a variety of substrates using only 5 mol % macrocycle was achieved.     

配位印迹聚合物在分析化学中的应用进展

分子印迹聚合物(MIP)是一种对目标分子(模板分子)具有选择性结合能力的聚合物.配位印迹聚合物(CIP)是基于金属离子与功能单体、模板分子间配位作用的分子印迹聚合物,既沿袭了MIP的优点,又具有适用于极性环境等优点,在食品、环境、生物、医药等领域目标物的识别中有良好的应用潜力.本文介绍了CIP的原理和特点,综述了CIP在分析化学中的应用进展,展望了CIP的发展前景.     

甲氧苄啶分子印迹涂层搅拌棒在复杂样品痕量甲氧苄啶和磺胺药物分析中的应用(英文)

研制了甲氧苄啶分子印迹吸附萃取搅拌棒涂层,并应用于复杂样品中痕量甲氧苄啶和磺胺药物的分析。分子印迹涂层的厚度约为21.5μm,相对标准偏差为5.9%(n=10),涂层均匀、致密,具有良好的热稳定性和化学稳定性。分子印迹涂层的萃取容量是非印迹涂层萃取容量的1.7倍,分子印迹涂层对抗菌增效剂、磺胺药物、三嗪化合物和甲氨蝶呤都表现出良好的选择性吸附萃取能力。建立了分子印迹吸附萃取搅拌棒联用高效液相色谱的分析方法,成功应用于加标尿样和血浆中痕量甲氧苄啶的分析,线性范围为5～200μg/L,检出限为1.6μg/L,在尿样和血浆中的回收率范围分别为84.5%～91.7%和71.9%～85.1%,标准偏差分别为2.9%～4.4%和3.0%～7.3%。该方法还应用于加标牛奶中痕量磺胺药物的分析,线性范围为10～200μg/L,检出限在4.5～6.1μg/L之间,回收率为83.2%～110.2%,标准偏差为4.1%～8.0%.     

基于还原石墨烯/纳米银复合材料的电化学传感器测定双酚A

石墨烯特有的褶皱层状结构以及银纳米粒子良好的催化性能,使其在电化学方面具有良好的应用潜能.本研究以柠檬酸钠为还原剂,通过水热反应原位制备出还原石墨烯/纳米银复合材料(rGO/AgNPs),用于修饰玻碳电极,研究了双酚A的电化学行为.循环伏安法(CV)和方波伏安法(SWV)的实验结果表明,双酚A可以在rGO/AgNPs修饰电极表面发生快速的氧化还原反应,基于此实现了对双酚A的高灵敏检测.在最优条件下,双酚A的氧化峰电流与其浓度在0.1~40.0μmol/L范围内呈良好的线性关系(r2=0.996),检出限为50.7 nmol/L(S/N=3).将其用于实际环境和塑料样品中双酚A的检测,回收率为91.7%~102.9%.     

Transfer matrix for the open chain from giant gravitons

We construct the transfer matrix for the open chain with the centrally extended SU(2|2) symmetry attached to the so called Z=0 giant graviton brane. Using the reflection equations, unitarity property and crossing property, we show that this model is integrable.     

简单结构超表面实现波长和偏振态同时复用全息显示新方法

本文基于衍射光学设计理论,提出了仅用一种简单结构实现波长和偏振态同时复用全息显示新方法.构建了不同入射条件下超表面微元的结构参数与透过相位之间的映射关系,建立了科学的评价函数,优化得到超表面每个像素点处最优的单一结构超表面微元尺寸.仿真结果表明,本文设计的超表面实现了波长为532 nm的x线偏振光和波长为633 nm的y线偏振光入射显示不同形状字符的功能.     

Synthesis and structure of N-methylated azacalix[4]pyridines and azacalix[1]arene[3]pyridines

Reaction of azacalix[4]pyridine and azacalix[1]arene[3]pyridine with methyl iodide afforded N-methylated products selectively and highly efficiently. Crystal structures revealed that the modified electronic nature of the pyridines could change the conjugation between the bridging nitrogen and the neighbouring aromatics.