High-performance sodium polyacrylate nanocomposites developed by using ionic liquid covalently modified multiwalled carbon nanotubes

Ionic liquids grafted with multiwalled-nanotubes (CNT Br/NTf₂), involving hydrophilic bromide salt and hydrophobic bis(trifluoromethanesulphonyl)imide salt, were prepared by amidation, followed by an easy solution-casting method of blending CNT Br/NTf₂ with sodium polyacrylate (PAA) as well as crosslinking agent (XR-100) to form PAA hybrid nanocomposites. The uniform dispersion of CNT Br/NTf₂ were analyzed by TEM. The defects and physical properties of fillers were characterized by Raman spectroscopy, Contact angle test, and TGA. Furthermore, microstructures of hybrid nanocomposites were characterized by SEM, from which it can be found that fillers were homogeneously distributed in the PAA matrix. CNT Br/NTf₂ significantly improved the mechanical properties and tensile fatigue resistance, as well as offered tunable swelling behavior of PAA nanocomposites without wasting too much of thermal stability. This study offers a simple approach to develop multifunctional materials based on ionic liquids covalently modified MWCNTs PAA nanocomposites.     

Bimetallic CuCo2S4 Nanozymes with Enhanced Peroxidase Activity at Neutral pH for Combating Burn Infections

Peroxidase-mimicking nanozymes that can generate toxic hydroxyl radicals (^.OH) hold great promise as antibacterial alternatives. However, most of them display optimal performance under strongly acidic conditions (pH 3–4), and are thus not feasible for many medical uses, including burn infections with a wound pH close to neutral. Herein, we report a copper-based nanozyme (CuCo₂S₄) that exhibits intrinsic peroxidase-like activity and can convert H₂O₂ into ^.OH at neutral pH. In particular, bimetallic CuCo₂S₄ nanoparticles (NPs) exhibited enhanced peroxidase-like activity and antibacterial capacity, superior to that of the corresponding monometallic CuS and CoS NPs. The CuCo₂S₄ nanozymes possessed excellent ability to kill various bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Furthermore, this CuCo₂S₄ nanozymes could effectively disrupt MRSA biofilms in vitro and accelerate MRSA-infected burn healing in vivo. This work provides a new peroxidase mimic to combat bacteria in neutral pH milieu and this CuCo₂S₄ nanozyme could be a promising antibacterial agent for the treatment of burn infections.     

Effect of energy density, pH and temperature on de-aggregation in nano-particles/water suspensions in high shear mixer

The effect of energy input, pH and temperature on de-aggregation of hydrophilic silicon dioxide powder (particle size 12 nm) in a high shear mixer was investigated. It has been found that de-aggregation is a two step process. Initially, at low energy input very large aggregates (3-1000 μm) are gradually broken into smaller secondary aggregates (2-100 μm) of a single modal size distributions. As the energy input increases primary aggregates (0.03-1 μm) are eroded from the secondary aggregates leading to bimodal size distributions with the first mode between 0.03 μm and 1 μm corresponding to the primary aggregates and the second mode between 2 μm and 100 μm corresponding to the secondary aggregates. At a sufficiently high energy density all secondary aggregates are broken into primary aggregates however, even at the highest energy density employed the primary aggregates could not be broken into single nano-particles. The temperature and the pH affect de-aggregation kinetics but do not alter de-aggregation pattern. Increasing pH at low temperature speeds up de-aggregation, whilst increasing pH at high temperature slows down de-aggregation process.     

PTA干燥机搅笼轴断裂原因及改进

介绍了PTA装置TA单元干燥机进料搅笼在运行中突然发生的轴断裂事故,从宏观检验、化学成分分析、金相检验、力学试验、宏观断口分析、静强度校核等方面进行了分析,找出了事故原因为疲劳断裂。从搅笼轴的结构和制造工艺上提出了改进方案,取得了良好的经济和社会效益。     

Self-assembly and Fractal Feature of Chitosan and Its Conjugate with Metal Ions: Cu (II)/Ag (I)

In this paper, we investigated the self-assembly and fractal feature of chitosan and Ag (I), Cu (II)-chitosan due to the theoretical and practical importance of chitosan in biomedical engineering, biomaterials and environmental sciences etc. The self-assembly and fractal structures of chitosan and Ag (I), Cu (II)-chitosan were observed using atomic force microscope (AFM), and the fractal dimensions of chitosan and Ag (I)-chitosan were calculated. The results indicate that their fractal dimension is approximate 2 and relates with the accumulation degree: the fractal dimension decreases with the accumulation degree increases. In addition, a new self-assembly strategy was presented to study the lyotropic liquid crystals (LLC) of chitosan and the formation mechanism of LLC was primarily analyzed and discussed. All of these results are valuable for the structure/function relationship study of chitosan and useful for application in biomedical materials.     

固定化黑曲霉生产柠檬酸的研究

将黑曲霉(Aspergillus niger)菌丝体及孢子联合包埋在海藻酸钙凝胶中,用于生产柠檬酸。确定了包埋固定化的最佳条件:海藻酸钠浓度2.0～2.5%,氯化钙浓度5.0～10.0%。确定了固定化微生物摇瓶发酵生产柠檬酸的条件为:蔗糖12%,发酵液初始pH 值3.0,培养温度35℃等。对固定化微生物半连续发酵生产柠檬酸进行了初步探索。     

令牌总线综合业务局域网的研制

这里介绍了一种窄带ISLN实验系统原型,描述了适合于实时业务和非实时业务综合需要的通信协议,并以统一的分组交换方式实现了话音/数据业务的综合。最后给出了实验结果。     

应用正交变换法求解裂缝性气藏水平井压力动态模型

本文应用正文变换法及矩阵微分方程的理论,较为容易地求解了裂缝性气藏水平井渗流的三个基本初边值问题,得到了形式简明的精确解。     

电磁铸造实验和数值模拟

通过实验室小型电磁铸造铝及其合金的冷、热态的实验和数值模拟并经工业装置的验证,研究了电磁结晶器内的磁场分布,液体金属柱成型特性.电磁结晶器及屏蔽罩结构的优化,铸造过程中金属液的温度场与流场并进行数值模拟.研究表明:为了稳定进行铸造,液柱的成型特性(液柱高度、形状和稳定性)必须达到一定要求.为了保证电磁铸造时金属液顺利成型,选择适当的功率,确保合适的磁场强度形成一定的推力是必要的.温度场的研究可以看出电磁铸造具有一系列特点,如强烈水冷、电磁搅拌、感应加热,使得电磁铸造中的凝固过程大大不同于普通的直接铸造法的凝固过程.流动场的分析说明,电磁铸造条件下应控制搅拌强度,以便获得良好的铸坯内部组织.