Characterization of Different Salt Forms of Chitooligosaccharides and Their Effects on Nitric Oxide Secretion by Macrophages

In this paper, chitooligosaccharides in different salt forms, such as chitooligosaccharide lactate, citrate, adipate, etc., were prepared by the microwave method. They were characterized by SEM, FTIR, NMR, etc., and the nitric oxide (NO) expression was determined in RAW 264.7 cells. The results showed that pure chitooligosaccharide was an irregular spherical shape with rough surface, and its different salt type products are amorphous solid with different honeycomb sizes. In addition to the characteristic absorption peaks of chitooligosaccharides, in FTIR, the characteristic absorption of carboxyl group, methylene group, and aromatic group in corresponding acid appeared. The characteristic absorption peaks of carbon in carboxyl group, hydrogen and carbon in methyl, methylene group, and aromatic group in corresponding acid also appeared in NMR. Therefore, the sugar ring structure and linking mode of chitooligosaccharides did not change after salt formation of chitooligosaccharides. Different salt chitooligosaccharides are completely different in promoting NO secretion by macrophages, and pure chitooligosaccharides are the best.     

一种适用于三相过程的高活性和高稳定性的甲醇合成催化剂

Methanol is one of the most important basic feedstock for the organic chemical industry and also is a potential fuel. Although the technology for the production of methanol is generally considered mature, much attention is still being paid to the improvements of the process, equipment and catalyst.     

基于参数变分原理的Cosserat连续体弹塑性分析

基于参数变分原理,提出了Cosserat模型弹塑性计算的算法,给出了基于Cosserat理论的参数最小势能原理,基于所提出的变分方程,建立了Cosserat理论弹塑性分析的参数二次规划模型,进一步将算法应用于平面应变软化问题计算中,获得的结果具有良好的非网格依赖性.     

Recyclable and transparent bacterial cellulose/hemiaminal dynamic covalent network polymer nanocomposite films

Recyclable and transparent nanocomposite films based on bacterial cellulose (BC) and hemiaminal dynamic covalent network polymer (HDCN) have been synthesized by in situ polymerization of 4,4′-diaminodiphenyl ether (ODA) with paraformaldehyde. Transparency and structural and mechanical properties of such nanocomposite films are investigated. It was found that BC/HDCN nanocomposite films exhibits a high optical transparency (86 % at 550 nm). Scanning electron microscopy reveals excellent compatibility of the reinforcement of BC nanofibers and HDCN matrix, which leads to the improvement of 20 and 200 % in tensile strength and storage modulus, respectively, as compared to neat HDCN films. BC hydrogels are readily recoverable from nanocomposite films by the sulphuric acid treatment and ODA monomer is deposited and also recycled.     

Graphene‐Fe3O4 as a magnetic solid‐phase extraction sorbent coupled to capillary electrophoresis for the determination of sulfonamides in milk

Graphene‐Fe₃O₄ nanoparticles were prepared using one‐step solvothermal method and characterized by X‐ray diffraction, FTIR spectroscopy, scanning electron microscopy, and vibrating sample magnetometry. The results demonstrated that Fe₃O₄ nanoparticles were homogeneously anchored on graphene nanosheets. The as‐synthesized graphene‐Fe₃O₄ nanoparticles were employed as sorbent for magnetic solid‐phase extraction of sulfonamides in milk prior to capillary electrophoresis analysis. The optimal capillary electrophoresis conditions were as follows: 60 mmol/L Na₂HPO₄ containing 2 mmol/L ethylenediaminetetraacetic acid disodium salt and 24% v/v methanol as running buffer, separation voltage of 14 kV, and detection wavelength of 270 nm. The parameters affecting extraction efficiency including desorption solution, the amount of graphene‐Fe₃O₄ nanoparticles, extraction time, and sample pH were investigated in detail. Under the optimal conditions, good linearity (5–200 μg/L) with correlation coefficients ≥0.9910 was obtained. The limits of detection were 0.89–2.31 μg/L. The relative standard deviations for intraday and interday analyses were 4.9–8.5 and 4.0–9.0%, respectively. The proposed method was successfully applied to the analysis of sulfonamides in milk samples with recoveries ranging from 62.7 to 104.8% and relative standard deviations less than 10.2%.     

Q235A钢用新型耐磨覆层材料的残余应力计算

计算了Q2 35A钢用新型耐磨金属陶瓷覆层材料的残余应力分布 ,通过对残余应力的计算发现覆层材料中的残余应力随覆层与基体厚度比的变化而变化。由于此种新型覆层材料的覆层厚度可不受限制 ,据此本文提出了可以对覆层材料的厚度进行优化 ,从而得到有利的残余应力分布的设计方案     

Bottom‐Up Fabrication of Single‐Layered Nitrogen‐Doped Graphene Quantum Dots through Intermolecular Carbonization Arrayed in a 2D Plane

A single‐layered intermolecular carbonization method was applied to synthesize single‐layered nitrogen‐doped graphene quantum dots (N‐GQDs) by using 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) as the only precursor. In this method, the gas produced in the pyrolysis of TATB assists with speeding up of the reactions and expanding the layered distance, so that it facilitates the formation of single‐layered N‐GQDs (about 80 %). The symmetric intermolecular carbonizations of TATB arrayed in a plane and six nitrogen‐containing groups ensure small, uniform sizes (2–5 nm) of the resulting products, and provide high nitrogen‐doping concentrations (N/C atomic ratio ca. 10.6 %). In addition to release of the produced gas, TATB is almost completely converted into aggregated N‐GQDs; thus, relatively higher production rates are possible with this approach. Investigations show that the as‐produced N‐GQDs have superior fluorescent characteristics; high water solubility, biocompatibility, and low toxicity; and are ready for potential applications, such as biomedical imaging and optoelectronic devices.     

PARAMETRIC VARIATIONAL PRINCIPLE BASED ELASTIC-PLASTIC ANALYSIS OF COSSERAT CONTINUUM

A new algorithm is developed based on the parametric variational principle for elastic-plastic analysis of Cosserat continuum. The governing equations of the classic elastic-plastic problem are regularized by adding rotational degrees of freedom to the conventional translational degrees of freedom in conventional continuum mechanics. The parametric potential energy principle of the Cosserat theory is developed, from which the finite element formulation of the Cosserat theory and the corresponding parametric quadratic programming model are constructed. Strain localization problems are computed and the mesh independent results are obtained.     

Preparation and ablation properties of ZrC-SiC coating for carbon/carbon composites by solid phase infiltration

A novel ZrC-SiC coating was prepared on carbon/carbon (C/C) composites surface by solid phase infiltration and the ablation properties of the ZrC-SiC coated C/C composites under oxyacetylene flame were studied. The results show that the coating prepared on the condition of optimum process parameters exhibits dense surface and outstanding anti-ablation ability. After ablation for 20 s, the mass ablation rates of the coated C/C composites can be lowered to 2.36 × 10⁻³ g/s, 37.1% reduction compared with uncoated C/C composites. The oxide layer composed of ZrO₂ and SiO₂ acts as oxygen diffusion barrier and the evaporation of ZrO₂ and SiO₂ absorbs a great amount of heat from the flame and reduces the erosive attack on the coating.     

RDX分形生长及其机理研究

使环三亚甲基三硝胺(RDX)溶液在非平衡态下结晶,制备具有分形结构的RDX.通过加入不同的醇类来调节溶液的粘度,改变溶剂挥发速度,从而控制分形生长的非平衡程度及分形形貌.研究结果表明:当在RDX的丙酮溶液中加入乙二醇时,RDX的结晶形貌随溶液浓度的增加呈分形树生长;当加入乙醇时,随着浓度的增加,RDX的结晶形貌发生了从...