Separation and Identification of Ergosta-4,6,8(14),22-tetraen-3-one from Ganoderma atrum by High-Speed Counter-Current Chromatography and Spectroscopic Methods

High speed counter-current chromatography in semi-preparative scale was used to separate and purify ergosta-4,6,8(14),22-tetraen-3-one from Ganoderma atrum, a famous traditional Chinese medicine. A two-phase solvent system composed of a mixture of n-hexane–ethanol–water (6: 5: 1, v/v/v) was used and the separation conditions were optimized. In a typical run in less than 400 min, 100 mg of samples can be separated to yield 14 mg of ergosta-4,6,8(14),22-tetraen-3-one with 99.1% purity. The structure of this compound was elucidated by UV, EI-MS, ¹H NMR and ¹³C NMR.

     

氢化物气相外延生长氮化镓单晶衬底的研究进展

氮化镓(GaN)晶体是制备蓝绿光激光器、射频微波器件以及电力电子等器件的理想衬底材料,在激光显示、5G通讯及智能电网等领域具有广阔的应用前景.目前市场上的氮化镓单晶衬底大部分都是通过氢化物气相外延(Hydride Vapor Phase Epitaxy,HVPE)方法生长制备的,在市场需求的推动下,近年来HVPE生长技术获得了快速的发展.本论文综述了近年来HVPE方法生长GaN单晶衬底的主要进展,主要内容包含HVPE生长GaN材料的基本原理、GaN单晶中的掺杂与光电性能调控、GaN单晶中的缺陷及其演变规律和GaN单晶衬底在器件中的应用.最后对HVPE生长方法的发展趋势进行了展望.     

共价有机框架材料催化研究进展

共价有机框架材料（COFs）是一类具有高比表面积、高孔隙率、高结晶度的结构多样性多孔材料.由于COFs具有可设计性、易功能化的特点，可通过“自上而下”或者后修饰策略将具有催化活性的官能团或金属颗粒嵌入到材料骨架当中，从而设计出高效催化剂.COFs已逐渐在多相催化及其它催化领域展现出非常大的应用价值.本文综述了COFs作为催化剂载体在多种催化反应中的合成策略与应用，对COFs催化剂的现状进行了总结与展望，同时指出该领域面临的问题与挑战.     

Interaction of a reflected shock from a concave wall with a flame distorted by an incident shock

Observations are presented from calculations where a laminar spherical CH₄/air flame was perturbed successively by incident and reflected shock waves reflected from a planar or concave wall. The two-dimensional axi-symmetric Navier–Stokes equations with detailed chemistry were used. The computational results were qualitatively validated with experiments which were performed in a standard shock tube arrangement. Under the influence of the incident shock wave, a Richtmyer–Meshkov instability is induced in the flame, and the distorted flame finally takes the form of two separated elliptical burning bubbles in the symmetric cross plane. Then, under subsequent interactions with the shock wave reflected from the planar or the concave wall, the flame takes a mushroom-like shape. Transverse waves produced by the shock reflection from the concave wall can compress the flame towards the axis, and the focusing shock generated on the concave wall will lead to a larger mushroom-like flame than that induced by the planar reflection.      

A boronic acid based glucose assay based on the suppression of the inner filter effect of gold nanoparticles on the orange fluorescence of graphene oxide quantum dots

Microchimica Acta - The authors describe a non-enzymatioc glucose assay that has three features: (a) The use of a boronic acid as the recognition element; (b) the aggregation of gold nanoparticles...     

STUDY ON NONLINEAR CONSTITUTIVE RELATIONSHIP AND FRACTURE BEHAVIOR OF STITCHED C/SiC COMPOSITES$^{\bf 1)}$

C/SiC复合材料具有高比强度、高比模量和优良的热稳定性能等一系列优点, 广泛应用于航空航天领域中. 裂纹扩展进而引起的脆性断裂是其主要失效形式之一, 因而材料的断裂性能分析对材料的结构设计和应用有重要的指导意义. 本文开展了缝合式C/SiC复合材料简单力学试验和断裂试验, 研究了材料在不同载荷下的力学响应及断裂特征. 基于缝合式C/SiC复合材料简单力学试验, 建立了材料宏观非线性损伤本构方程, 并模拟了缝合式C/SiC复合材料单边切口梁和双悬臂梁的断裂行为. 本构方程采用简单函数描述了材料在复杂应力状态下的非线性应力-应变曲线, 并考虑了反向加载过程中造成的裂纹闭合. 基于商业有限元软件ABAQUS, 通过编写UMAT子程序实现非线性损伤本构方程, 采用单个单元验证了建立的本构方程的有效性. 在此基础上, 采用线弹性损伤本构和非线性损伤本构分别模拟了缝合式C/SiC复合材料单边切口梁和双悬臂梁的断裂行为. 采用非线性损伤本构方程模拟的力-位移曲线结果与试验结果更为吻合, 非线性损伤本构预测的失效载荷与试验失效载荷更为接近, 验证了所建立的非线性损伤本构方程的准确性, 为C/SiC复合材料断裂行为的研究提供了借鉴, 为缝合式C/SiC复合材料结构的设计和应用提供了理论基础.     

Bioadhesive hydrocaffeic acid modified chitosan colloidal particles using as particulate emulsifiers

A kind of bioadhesive hydrocaffeic acid modified chitosan colloidal particles (HCA-CS/TPP CPs) containing synthetic catecholamine groups was prepared via amidation reaction and ionic gelation. The formation process and property of the HCA-CS/TPP CPs were characterized by ultraviolet visible spectrophotometry and Zeta PALS instruments. The prepared HCA-CS/TPP CPs were then used as particulate emulsifier to stabilize Pickering emulsions. The stability of the Pickering emulsion droplet was characterized by digital camera and optical microscope. The results revealed that HCA-CS/TPP CPs exhibited good emulsifying property at a wide pH value range, which will endow the potential application of the Pickering emulsions stabilized by HCA-CS/TPP CPs in various fields.     

Numerical investigation on the rotating detonation critical mode for a methane–air mixture in an annular tube using reactive Navier–Stokes equations

Journal of Thermal Analysis and Calorimetry - Previous experimental studies show that gaseous detonation propagation in an annular tube can be divided into three categories, i.e., stable mode,...     

Nanofiber Configuration of Electrospun Scaffolds Dictating Cell Behaviors and Cell-scaffold Interactions

Electrospun nanofibers are of the same length scale as the native extracellular matrix and have been extensively reported to facilitate adhesion and proliferation of cells and to promote tissue repair and regeneration. With a primary focus on tissue repair and regeneration using electrospun scaffolds, only a few studies involved electrospun nanofiber scaffolds directing cell behaviors have been reported. In this study, we prepared electrospun nanofiber scaffolds with distinct fiber configurations, namely, random and aligned orientations of nanofibers, as well as oriented yarns, and investigated their effects on cell behaviors. Our results showed that these scaffolds supported good proliferation and viability of murine fibroblasts. Fiber configuration profoundly influenced cell morpho-logy and orientation but showed no effects on cell proliferation rate. The yarn scaffold had comparable total protein accumulation with the random and aligned scaffolds, but it supported a greater pro-liferation rate of fibroblasts with significantly elevated collagen de-position due to its porous fibrous configuration. Cell-seeded yarn scaffolds showed a greater Young's modulus compared with cell-free controls as early as 1 week. Together with its unique fiber configuration similar to the native extracellular matrix of the myocardium, the yarn scaffold might be a suitable matrix material for modeling cardiac fibrotic disorders.