Engineered pH-inducible intein Mtu ΔI-CM variants with markedly reduced premature cleavage activity

Inteins have been widely exploited for the purification of tagless proteins. Among them, pH-inducible C-terminal-cleavage inteins enable the preparation of proteins and peptides with an authentic N-terminus. However, a severe premature cleavage around neutral pH has limited the application of these inteins, especially when used in recombinant hosts such as Escherichia coli. By targeting the microenvironment of the two key histidine residues H429 and H439, we engineered Mtu ΔI-CM intein to markedly reduce its premature cleavage. Kinetic analyses suggested that although the variants retained the pH dependence, they indeed cleaved slower, especially at pH 7.6. These variants resulted in higher yields for two model polypeptides than the original Mtu ΔI-CM intein, when used in conjunction with a cleavable self-assembling tag. This work suggests that more controllable pH-inducible inteins can be obtained by manipulating the residues in the self-cleavage sites and provide better performance for tag-based protein preparation strategies.     

A novel flow field with controllable pressure gradient to enhance mass transport and water removal of PEM fuel cells

An easily machined novel flow field with controllable pressure gradient across adjacent channels was designed and a two dimensional, across-the-channel, two-phase model was developed to study the gas transport and water removal of the novel configuration. The effect of channel-rib width ratio, GDL thickness and pressure gradient on the profiles of oxygen concentration and water saturation within the GDL were investigated. Special attention was paid to the mechanisms of the promoted mass transport and water removal rates under a pressure gradient. The model was validated by experiments with various channel-rib ratios and GDL thicknesses at different operating pressure. The results revealed that, oxygen concentration was increased, and the water saturation was reduced under the rib with a pressure gradient generated across the adjacent channels. The optimal pressure gradient is between 0.1 to 0.2 atm for the studied channel geometry and configuration. The mechanisms of the improved cell performance were elucidated.     

Sintering behavior of a nanostructured thermal barrier coating deposited using electro-sprayed particles

During high temperature service, a series of microstructure and phase evolutions occur in thermal barrier coatings (TBCs), which result in degradation of thermal insulation and durability. In this study, the sintering behavior of an air plasma sprayed 8 wt% YSZ coating deposited using electro-sprayed nanostructured particles (ESP) as feedstock powder was investigated and compared with conventional YSZ coating deposited using hollow spherical powders (HOSP). Due to the distinct asymmetric porous structure formed by nanosized YSZ particles, the ESP powder was partially melted in the plasma jet during the deposition, which resulted in the formation of a nanostructured coating that consisted of porous nanozones and dense zones. The ESP coating not only shows a significantly lower initial thermal conductivity of 0.70 W/mK, but also exhibits a stronger sintering resistance in terms of phase stability and thermal insulation compared to the conventional coating. When subjected to prolonged sintering at 1400°C for 128 hours, the thermal conductivity of the ESP coating would gradually increase to about half that of the HOSP coating at 1.29 W/mK. These differences are ascribed to the interaction among different sintering behavior between nanozones and dense zones.     

A novel efficient RhB absorbent of Mo2N/MoO2 composite nanofibers for wastewater treatment

Mo₂N/MoO₂ composite nanofibers have been prepared via an electrospinning and controlled nitridation process. The composite nanofibers exhibit a highly efficient Rhodamine B (RhB) absorption behavior with a rate constant of 0.153 g min⁻¹ mg⁻¹, which is about 20 times of the commercial-activated carbon material. Furthermore, the nanofibers show stable absorption activity after recycled by an environmental friendly procedure for four times. The excellent absorption performance of Mo₂N/MoO₂ composite nanofibers demonstrates a promising application of Mo₂N-related materials as an absorbent for wastewater treatment.     

溶剂洗涤法脱除聚丙烯中的灰分

设计了"烷烃+醇+络合剂"的三组分复配溶剂体系,利用其洗涤脱除聚丙烯中的灰分,达到了降低Ti,Mg,Al等金属残留含量进而提高聚丙烯纯度的目的。研究了洗涤剂种类、复配方式、洗涤时间、洗涤温度等对灰分脱除效果的影响。结果表明:利用正己烷/乙酰丙酮/乙醇三组分溶剂洗涤聚丙烯,总灰分含量降至38 μg/g,灰分脱除率达到50.1%,聚丙烯纯度得到显著提升。     

Phenol hydrogenation to cyclohexanone over palladium nanoparticles loaded on charming activated carbon adjusted by facile heat treatment

Selective phenol hydrogenation is a green approach to produce cyclohexanone. It still remains a big challenge to prepare efficient supports of the catalysts for the phenol hydrogenation via a simple and cost-effective approach. Herein, a facile approach was developed, i.e., direct calcination of activated carbon (AC) under argon at high temperature, to improve its structure and surface properties. The modified AC materials were supported with Pd nanoparticles (NPs) to fabricate the Pd/C catalysts. The as-prepared Pd/C600 catalyst exhibits superior catalytic performance in the phenol hydrogenation, and its turnover frequency (TOF) value is 199.2 h⁻¹, 1.31 times to that of Pd/C-raw. The Pd/C600 catalyst presents both better hydrophobicity and more structural defects, contributing to the improved dispersibility in the reaction solution (phenol-cyclohexane), the better Pd dispersion and the smaller Pd size, which result in the enhancement of the catalytic performance. Furthermore, the as-prepared Pd/C600 catalyst shows a good recyclability.     

双子(Gemini)表面活性剂合成及研究进展

综述了阳离子型、阴离子型、非离子型和两性离子型四类双子表面活性剂的合成及研究进展,指出未来双子表面活性剂研究的主要方向为获得更高的表面活性、降低合成和使用成本、不同类型的表面活性剂协同强化、提高安全环保性和拓宽应用领域等。     

丁烷氧化反应器装置数据分析与优化

基于丁烷氧化反应器的实际装置数据,经预处理后,采用主成分分析进行数据挖掘。结果表明,可利用该方法来筛选及判断异常数据点,从而可用于反应器状态的实时诊断和预警,同时对反应器输入和输出参数之间的相关性进行分析,理解和把握参数之间的变化特征,发现丁烷转化率与反应器出口的CO/CO2比值呈负相关,体现主反应和副反应的选择性问题,从而可用于指导反应器操作优化等。