Solvent vapor annealing of block copolymer thin films: removal of processing history

The ordering processes of PS-b-P2VP block copolymer thin films with different processing histories were studied during solvent vapor annealing by in situ grazing incidence small-angle X-ray scattering (GISAXS). We compared cylinder-forming PS-b-P2VP thin films with 34 kg/mol molecular weight that were prepared in three different ways: spin coating, spin coating and subsequent solvent vapor annealing where the solvent vapor was removed instantaneously, and spin coating and subsequent solvent vapor annealing where the solvent vapor was removed slowly. Block copolymer thin films retained the morphology resulting from the different “processing histories” at smaller swelling ratios. This processing history was erased when the samples reached a higher swelling ratio (~1.4). After the solvent was slowly removed from the swollen film, the surface morphology was characterized by ex situ AFM. All samples showed the same morphology after solvent annealing regardless of the initial morphology, indicating the morphology of solvent annealed samples is determined by the polymer concentration in the swollen film and the solvent vapor removal rate, but not the processing history.     

Fluorocarbon-bonded magnetic mesoporous microspheres for the analysis of perfluorinated compounds in human serum by high-performance liquid chromatography coupled to tandem mass spectrometry

We report herein an extraction method for the analysis of perfluorinated compounds in human serum based on magnetic core–mesoporous shell microspheres with decyl-perfluorinated interior pore-walls (Fe₃O₄@mSiO₂-F₁₇). Thanks to the unique properties of the Fe₃O₄@mSiO₂-F₁₇ microspheres, macromolecules like proteins could be easily excluded from the mesoporous channels due to size exclusion effect, and perfluorinated compounds (PFCs) in protein-rich biosamples such as serum could thus be directly extracted with the fluorocarbon modified on the channel wall without any other pretreatment procedure. The PFCs adsorbed Fe₃O₄@mSiO₂-F₁₇ microspheres could then be simply and rapidly isolated by using a magnet, followed by being identified and quantified by LC–MS/MS (high-performance liquid chromatography coupled to tandem mass spectrometry). Five perfluorinatedcarboxylic acids (C6, C8–C11) and perfluorooctane sulfonate (PFOS) were selected as model analytes. In order to achieve the best extraction efficiency, some important factors including the amount of Fe₃O₄@mSiO₂-F₁₇ microspheres added, adsorption time, type of elution solvent, eluting solvent volume and elution time were investigated. The ranges of the LOD were 0.02–0.05 ng mL⁻¹ for the six PFCs. The recovery of the optimized method varies from 83.13% to 92.42% for human serum samples.     

含吲哚骨架的磷酰亚甲基衍生物的构建新策略

在金属碱催化作用下,本文成功实现了吲哚烯酰基化合物与二苯基氧膦P-H键的加成反应,并通过对催化剂、反应溶剂、反应时间、催化剂用量等影响因素的筛选,探索了反应的最佳条件,并在最佳条件下催化合成了一系列含吲哚骨架的磷酰亚甲基化合物,获得了较好的产率。该反应条件温和、产率高、反应迅速,为C(sp3)-P键的构筑提供了一种绿色高效的新方法。     

基于FPGA与Matlab的数字正交解调器的设计

为有效提取测控系统输入信号的幅度和相位信息,设计了基于FPGA与Matlab的信号数参考文献6文献类型、文献出处、年份字正交解调器。在Matlab/Simulink环境中产生一路调幅信号,并在此环境下利用5个直接I型的4阶FIR滤波器节搭建了20阶FIR滤波器;利用FPGA查表法实现数控振荡器(NCO),并控制1路调幅信号与正交的正、余弦信号分别进行数字混频处理;对经FPGA数字混频处理后的两路倍频分量和基频分量信号进行滤波处理,经处理后的信号在FPGA的控制下进行相加处理。最后在硬件平台上进行了仿真测试实验,验证了该方案的正确性和可行性。     

Hysteretic deteriorating model for quasi-brittle materials based on micromechanical damage approach

A damage model, which is based on the stochastic modeling of the microstructures, is developed for the quasi-brittle materials subjected to repeated loading. According to this model, the overall response of the material is represented with a series of micro-elements joined in parallel. A combined model is proposed for the micro-element considering the fracture as well as the hysteretic energy dissipation. To account for the progressive failure, the random fracture strains are assigned to the micro-elements. Therefore the overall parallel bundle is considered as a stationary random field. Then by averaging the microscopic random field, the overall loading, unloading and reloading curves are derived analytically. Two hysteretic rules are derived from the proposed model, and the overall hysteretic deteriorating behaviors could be well reproduced. To demonstrate the validity of the present model, the numerical results are shown against the stochastic simulated curves as well as the experimental data. The present model provides an alternative approach for the efficient modeling of the hysteretic deteriorating behaviors for the quasi-brittle materials.     

Micro-cracks informed damage models for brittle solids

A class of micro-cracks informed damage models for describing the softening behavior of brittle solids is proposed, in which damage evolution is treated as a consequence of micro-crack propagation. The homogenized stress–strain relation in the cracked microscopic cell defines the degradation tensor, which can be obtained by the equivalence between the averaged strain energy of the microscopic cell and the strain energy density of the homogenized material. This energy equivalence relationship serves as an energy bridging vehicle between the damaged continuum and the cracked microstructure. Several damage evolution equations are obtained by this energy bridging method. The size effect of the micro-cracks informed damage law is characterized through the microscopic cell analysis, and the proper scaling of the characterized damage evolution functions to eliminate mesh dependency in the continuum solution is introduced.     

N-heterocyclic carbene and Brønsted acid cooperative catalysis: asymmetric synthesis of trans-γ-lactams

An efficient enantioselective approach to form trans-γ-lactams in up to 99% yield, 93% ee, and >20/1 dr using unactivated imines has been developed. The cyclohexyl-substituted azolium and the weak base sodium o-chlorobenzoate are most suitable for this transformation. Notably, the process involves cooperative catalysis by an N-heterocyclic carbene and a Br?nsted acid.     

A colorimetric and ratiometric fluorescent probe for quantification of bovine serum albumin

A 4-aminonaphthalimide-based ratiometric fluorescent probe 1 employing the internal charge transfer (ICT) mechanism was designed and synthesized to detect bovine serum albumin (BSA). The interaction of 1 and BSA was investigated by fluorescence and UV-vis absorption spectroscopy. Upon treatment with BSA, the probe successfully exhibited a ratiometric fluorescent response at 540 nm and 480 nm. The fluorescent intensity ratio at 540 nm and 480 nm (F(540)/F(480)) increases linearly with BSA concentration in the range of 0-75.0 μg mL(-1) and the detection limit was about 2.4 ng mL(-1). Our strategy is expected to provide a methodology to quantify BSA either by a normal or by a ratiometric and colorimetric way with high sensitivity.     

混凝土黏塑性动力损伤本构关系

从静力弹塑性损伤本构关系的基本框架出发, 综合考虑塑性应变与损伤 演化的率敏感性, 建立了能够较为全面地描述混凝土在动力加载条件下非线性性能的混凝土 黏塑性动力损伤本构模型. 为了考虑塑性应变的率敏感性, 基于Perzyna理论推导了有效应 力空间黏塑性力学基本公式, 采用改进的Perzyna型动力演化方程, 将损伤静力演化方程推 广到动力加载情形. 基于并联弹簧模型, 从概率论的角度推导给出了一维损伤静力演化方程, 并基于能量等效应变的基本概念将其推广到多维损伤演化. 利用数值模拟, 计算得到了 混凝土在不同应变率下的应力应变全曲线, 同时得到了一维动力提高因子和二维动力强度包 络图, 数值结果与试验结果的对比表明了该模型的有效性.     

Simultaneous determination of 5'-monophosphate nucleotides in infant formulas by HPLC-MS

A method was developed for simultaneous determination of 5'-monophosphate nucleotides, adenosine 5'-monophosphate, cytidine 5'-monophosphate, guanosine 5'-monophosphate, inosine 5'-monophosphate, and uridine 5'-monophosphate in infant formulas by high-performance liquid chromatography-mass spectrometry equipped with electrospray ionization source. The complete chromatographic separation of five nucleotides was achieved through a Symmetry C(18) column, after a binary gradient elution with water containing 0.1% formic acid and acetonitrile as mobile phase. The multi-reaction monitoring mode was applied for tandem mass spectrometry analysis. The established method was further validated by determining the linearity (R(2) > 0.999), recovery (92.0-105.0%), and precision (relative standard deviation ≤6.97%). To verify the applicability of the method, thirty commercially available infant formulas were randomly purchased from the supermarkets in Hangzhou, China, and then analyzed. The results showed that the developed method is validated, sensitive, and reliable for quantitation of nucleotides in infant formulas.