基于甲磺酰基的磺酰胺-氨醇作为催化醛的不对称炔基化反应新配体

 以商业易得的 (–)-麻黄碱、(+)-伪麻黄碱和各种手性氨醇为主要原料, 经过简单的两步反应, 合成了一系列基于甲磺酰基的磺酰胺-氨醇 (SAA) 配体, 并将其用于催化苯乙炔基锌对醛的不对称加成反应. 在没有 Ti(OiPr)4 等金属试剂的条件下, 配体表现出较好的不对称诱导能力, 取得了高达 83% ee.     

The Structure and Optical Properties of the [Au18(SR)14] Nanocluster

Decreasing the core size is one of the best ways to study the evolution from Au^I complexes into Au nanoclusters. Toward this goal, we successfully synthesized the [Au₁₈(SC₆H₁₁)₁₄] nanocluster using the [Au₁₈(SG)₁₄] (SG=L ‐glutathione) nanocluster as the starting material to react with cyclohexylthiol, and determined the X‐ray structure of the cyclohexylthiol‐protected [Au₁₈(C₆H₁₁S)₁₄] nanocluster. The [Au₁₈(SR)₁₄] cluster has a Au₉ bi‐octahedral kernel (or inner core). This Au₉ inner core is built by two octahedral Au₆ cores sharing one triangular face. One transitional gold atom is found in the Au₉ core, which can also be considered as part of the Au₄(SR)₅ staple motif. These findings offer new insight in terms of understanding the evolution from [Au^I(SR)] complexes into Au nanoclusters.     

轴向均布载荷下压杆稳定问题的DQ解

叙述了微分求积法(differential quadrature method)的一般方法，研究用微分求积法求解在均布轴向载荷下细长杆的稳定问题．通过Newton-Raphson法求解非线性方程组，以及对问题进行线性假设后求解广义特征值方程，得到了精度很高的后屈曲挠度数值和临界载荷数值．与解析解和其他近似解相比，微分求积法具有较高的精度和简便性．     

Static yield stress of ferrofluid-based magnetorheological fluids

In this work, the yield stress of ferrofluid-based magnetorheological fluids (F-MRF) was investigated. The fluids are composed of a ferrofluid as the liquid carrier and micro-sized iron particles as magnetic particles. The physical and magnetorheological properties of the F-MRF have been investigated and compared with a commercial mineral oil-based MR fluid. With the addition of a ferrofluid, the anti-sedimentation property of the commercial MR fluids could be significantly improved. The static yield stress of the F-MRF samples with four different weight fractions (ϕ) of micro-sized iron particles were measured using three different testing modes under various magnetic fields. The effects of weight fraction, magnetic strength, and test mode on the yielding stress have been systematically studied. Finally, a scaling relation, , was proposed for the yield stress modeling of the F-MRF system.     

A Chemiluminescence Microarray Based on Catalysis by CeO2 Nanoparticles and Its Application to Determine the Rate of Removal of Hydrogen Peroxide by Human Erythrocytes

In this work, cerium oxide nanoparticles are capable of strongly enhancing the chemiluminescence (CL) of the luminol–hydrogen peroxide (H₂O₂) system. Based on this, a microarray CL method for the determination of the removal rate constant of H₂O₂ by human erythrocytes has been developed. It is providing direct evidence for a H₂O₂-removing enzyme in human erythrocytes that acts as the predominant catalyst. A reaction mechanism is discussed. The proposed microarray CL method is sensitive, selective, simple and time-saving, and has good reproducibility and high throughput. Relative CL intensity is linearly related to the concentration of H₂O₂ in the range from 0.01 to 50 μM. The limit of detection is as low as 6.5?×?10^?11 M (3σ), and the relative standard deviation is 2. 1 % at 1 μM levels of H₂O₂ (for n?=?11).     

A facile and efficient one‐step strategy for the preparation of β‐cyclodextrin monoliths

A novel, facile, and efficient one‐step copolymerization strategy was developed for the preparation of β‐cyclodextrin (β‐CD) methacrylate monolithic columns using click chemistry. The novel mono‐(1H‐1,2,3‐triazol‐4‐ylmethyl)‐2‐methylacryl‐β‐CD monomer was synthesized by a click reaction between propargyl methacrylate and mono‐6‐azido‐β‐CD, and then monolithic columns were prepared through a one‐step in situ copolymerization of the mono‐(1H‐1,2,3‐triazol‐4‐ylmethyl)‐2‐methylacryl‐β‐CD monomer and ethylene dimethacrylate. The physicochemical properties and column performance of the fabricated monolithic columns were characterized by elemental analysis, SEM, and micro‐HPLC. Satisfactory column permeability, efficiency, and separation performance were obtained for the optimized poly(mono‐(1H‐1,2,3‐triazol‐4‐ylmethyl)‐2‐methylacryl‐β‐CD‐co‐ethylene dimethacrylate) monolithic columns. Additionally, typical hydrophilic interaction chromatography retention behavior was observed on the monoliths at high acetonitrile content in the mobile phase. Although the enantioselectivity of our monolithic columns did not meet the level of other reported β‐CD monolithic columns, this one‐step strategy based on click chemistry still provides an interesting and effective model as it offers the possibility to easily prepare related novel CD methacrylate monoliths through a one‐step copolymerization strategy.     

A 200‐fold Quantum Yield Boost in the Photoluminescence of Silver‐Doped AgxAu25−x Nanoclusters: The 13 th Silver Atom Matters

The rod‐shaped Au₂₅ nanocluster possesses a low photoluminescence quantum yield (QY=0.1 %) and hence is not of practical use in bioimaging and related applications. Herein, we show that substituting silver atoms for gold in the 25‐atom matrix can drastically enhance the photoluminescence. The obtained Ag_xAu_25?x (x=1–13) nanoclusters exhibit high quantum yield (QY=40.1 %), which is in striking contrast with the normally weakly luminescent Ag_xAu_25?x species (x=1–12, QY=0.21 %). X‐ray crystallography further determines the substitution sites of Ag atoms in the Ag_xAu_25?x cluster through partial occupancy analysis, which provides further insight into the mechanism of photoluminescence enhancement.     

含腐蚀缺陷的管道静力性能试验测试研究

为研究腐蚀缺陷对管道承载力的影响,本文分别进行了含腐蚀缺陷管道在轴压载荷、弯曲载荷以及轴压和弯曲复合载荷作用下的静力失效过程测试。通过不同载荷作用下管道的荷载-位移曲线以及荷载-应变曲线来分析管道的失效模式和失效机理;通过有限元分析结果与试验测试结果验证其准确性。结果表明:腐蚀缺陷使管道在三种不同荷载作用下的极限承载力均有所下降;针对文中所研究的管道及其腐蚀缺陷,在轴压载荷作用下管道承载力下降了18.4%,在弯曲载荷作用下管道承载力下降了20.96%,在轴压和弯曲复合载荷作用下管道承载力下降了13.3%;管道中腐蚀缺陷位置的管壁厚度减小,该位置应变发展迅速,首先进入塑性屈服状态,最终导致该腐蚀位置发生弹塑性屈曲失效。