Flow-induced shear stress and deformation of a core–shell-structured microcapsule in a microchannel

A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications.     

Periodic solutions of a periodic stochastic human immunodeficiency virus model with distributed delay and cytotoxic T lymphocytes immune response

In this paper, a periodic stochastic human immunodeficiency virus (HIV) model with distributed delay and cytotoxic T lymphocytes (CTL) immune response is investigated. First, by It $ô$'s formula, we show that the solution with any positive initial value is global and positive. Then, by the stochastic comparison theorem, we obtain the sufficient conditions guaranteeing the existence and global attractivity of infection-free periodic solution. Furthermore, we discuss the existence of the infective periodic solution by Has'minskii theory. Finally, numerical examples are given to illustrate the results.     

Recent Progress of Small-Molecule Ratiometric Fluorescent Probes for Peroxynitrite in Biological Systems

Peroxynitrite (ONOO⁻) as a major reactive oxygen species plays important roles in cellular signal transduction and homeostatic regulation. Precise detection of ONOO⁻ in biological systems is vital for exploring its physiological and pathological function. Among numerous detection methods, fluorescence imaging technology using fluorescent probes offers some advantages, including simple operation, high sensitivity and selectivity, as well as real-time and nondestructive detection. In particular, ratiometric fluorescent probes, in which the built-in calibration of the two emission bands prevents interference from the biological environment, have been extensively employed to monitor the fluctuation of bioactive species. In this review, we will discuss small-molecule ratiometric fluorescent probes for ONOO⁻ in live cells or in vivo, which involves chemical structures, response mechanisms, and biological applications. Moreover, the challenges and future prospects of ONOO⁻-responsive ratiometric fluorescent probe are also proposed.     

Highly Active Hydrogen-rich Photothermal Reverse Water Gas Shift Reaction on Ni/LaInO3 Perovskite Catalysts with Near-unity Selectivity

Photo-assisted reverse water gas shift (RWGS) reaction is regarded green and promising in controlling the reaction gas ratio in Fischer Tropsch synthesis. But it is inclined to produce more byproducts in high H₂ concentration condition. Herein, LaInO₃ loaded with Ni-nanoparticles (Ni NPs) was designed to obtain an efficient photothermal RWGS reaction rate, where LaInO₃ was enriched with oxygen vacancies to roundly adsorbing CO₂ and the strong interaction with Ni NPs endowed the catalysts with powerful H₂ activity. The optimized catalyst performed a large CO yield rate (1314 mmol g_Ni⁻¹ h⁻¹) and ≈100 % selectivity. In situ characterizations demonstrated a COOH* pathway of the reaction and photoinduced charge transfer process for reducing the RWGS reaction active energy. Our work provides valuable insights on the construction of catalysts concerning products selectivity and photoelectronic activating mechanism on CO₂ hydrogenation.     

吲哚多样化环化合成咔唑衍生物研究进展

咔唑是一类特殊的含氮芳杂环分子,咔唑衍生物理化性质独特、结构多样,在天然产物、药物和功能材料领域有着广阔的应用,其合成方法一直备受关注.从吲哚直接环化到咔唑的合成方法简洁高效,原料廉价易得、产物种类多样.总结了近5年来以2,3-未取代吲哚为原料合成咔唑衍生物的方法,典型环化策略包含以下三种:[2+2′+2′]环化反应、[2+2′+2″]环化反应和[4+2]苯环化反应,探讨了每种方法的特点,并对未来的发展前景进行展望.     

Extraction and Analysis of Six Effective Components in Glycyrrhiza uralensis Fisch by Deep Eutectic Solvents (DES) Combined with Quantitative Analysis of Multi-Components by Single Marker (QAMS) Method

Deep eutectic solvents (DESs) are green organic solvents that have broad prospects in the extraction of effective components of traditional Chinese medicine. This work employed the quantitative analysis of multi-components by a single marker (QAMS) method to quantitatively determine the six effective components of glycyrrhizic acid, liquiritin, isoliquiritin apioside, liquiritigenin, isoliquiritin, and glycyrrhetinic acid in Glycyrrhiza uralensis, which was used for comprehensive evaluation of the optimal extraction process by DESs. First, Choline Chloride: Lactic Acid (ChCl-LA, molar ratio 1:1) was selected as the most suitable DES by comparing the extraction yields of different DESs. Second, the extraction protocol was investigated by extraction time, extraction temperature, liquid-to-material ratio, molar ratio, and ultrasonic power. The Box–Behnken design (BBD) combined with response surface methodology (RSM) was used to investigate the optimal DES conditions. The result showed that the best DES system was 1.3-butanediol/choline chloride (ChCl) with the molar ratio of 4:1. The optimal extraction process of licorice was 20 mL/g, the water content was 30%, and the extraction time was 41 min. The comprehensive impact factor (z) was 0.92. At the same time, it was found that the microstructure of the residue extracted by the eutectic solvent was more severely damaged than the residue after the traditional solvent extraction through observation under an electron microscope. The DES has the characteristics of high efficiency and rapidity as an extraction solution.     

柠檬酸镧的合成及其对SBR橡胶硫化性能的影响

以氯化镧和柠檬酸为原料,合成柠檬酸镧,探究反应条件对柠檬酸镧产率的影响,得到反应体系p H值4~5之间,柠檬酸与氯化镧的摩尔比1.2∶1,反应体系温度50℃为较优的反应条件。并将合成的柠檬酸镧添加到SBR混炼胶中,研究其对混炼胶的硫化特性和硫化胶物理机械性能的影响;结果表明,添加2.5%的柠檬酸镧可使混炼胶的硫化速率t90达到943 s,比未添加柠檬酸镧的快了31 s,当添加量为7.5%时硫化胶的物理机械性能达到最佳,比未添加相比提高了将近50%。通过红外光谱表征产物结构,并采用硫化仪、万能试验机对混炼胶进行硫化性能及物理机械性能测试,研究结果表明,柠檬酸镧可提高混炼胶的硫化性能、硫化胶物理机械性能及抗硫化还原性。因此,柠檬酸镧可以作为SBR橡胶硫化剂的一种补充。     

Non‐Covalent Functionalization of Graphene with Bisphenol A for High‐Performance Supercapacitors

The reduced graphene oxide (RGO)/bisphenol A (BPA) composites were prepared by an adsorption‐reduction method. The composites are characterized by X‐ray diffraction (XRD), UV‐vis, thermogravimetric (TG) analysis, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The results confirm that BPA is adsorbed on the basal plane of RGO by π‐π stacking interaction. Furthermore, the electrochemical behaviors were evaluated by cyclic voltammetry, galvanostatic charge/discharge techniques and electrochemical impedance spectroscopy (EIS). The results show that the RGO/BPA nanocomposites exhibit ultrahigh specific capacitance of 466 F·g^?1 at a current density of 1 A·g^?1, excellent rate capability (more than 81% retention at 10 A·g^?1 relative to 1 A·g^?1) and superior cycling stability (90% capacitance decay after 4000 cycles). Consequently, the RGO/BPA nanocomposites can be regarded as promising electrode materials for supercapacitor applications.     

各向异性弹塑性中厚度板壳的有限元分析

本文在文献［２，３］的基础上，提出了一个解各向异性弹塑性中厚度板壳问题的有限元方法。考虑材料各向异性的特点，采用了Ｈｉｌｌ推广的Ｈｕｂｅｒ－Ｍｉｓｅｓ屈服准则；借用Ｏｗｅｎ的剪切修正系数，正确计及了叠层复合材料壳体的横向剪切效应；为了避免“自锁”现象，文中采用了９节点的Ｈｅｔｅｒｏｓｉｓ二次壳单元；特别是本文利用插值外推的思想，提出了一个带预测的弧长增量控制法，显著提高了确定变形路径的计算效率。几个数值算例表明本文给出的有限元方法对于各向异性中厚度板壳的弹塑性分析有较好的精度，尤其是对具有复杂变形路径的结构计算，收敛速度提高更快。     

延性材料平面冲击波基本实验数值模拟的若干问题

假设屈服强度正比于剪切模量,分别构建了四种强度模型,并用于数值模拟Ly12铝的平面冲击波试验的质点速度剖面以及钨合金的平面冲击波试验的锰铜计应力记录.研究发现,基于Steinberg等的屈服强度模型比较符合实验.还对平面冲击波试验的层裂现象进行了简化的数值模拟,其中,采用了该文作者所提出的一种基于空穴聚集的层裂模型,该模型的特点是分别引入了层裂过程的早期及后期应力松弛方程.