豇豆血红蛋白Lb II在大肠杆菌中的重组表达条件优化、纯化与鉴定

豇豆根瘤中含有大量豆血红蛋白。该蛋白是良好的天然色素,可用于人造肉的着色,本文将携带豇豆血红蛋白Lb II基因的质粒pET-15b转化进入大肠杆菌BL21中表达,并对表达条件进行优化。通过查找NCBI数据库得到一条全长456 bp的豇豆血红蛋白Lb II的序列,以pET-15b作为表达载体,大肠杆菌BL21-CodonPlus （DE3）-R-IL作为重组工程菌进行表达,成功表达出豇豆血红蛋白Lb II,并使用镍柱层析对蛋白进行初步纯化,同时添加抗坏血酸为抗氧化剂。以IPTG浓度、温度、时间为自变量,Lb II表达量为因变量进行单因素实验。结果表明,在IPTG终浓度为1.0 mmol/L、诱导温度为25 ℃,时间为14 h时,重组豆血红蛋白Lb II的表达量最高,经SDS-PAGE凝胶电泳和可见光光谱分析法鉴定为目的蛋白Lb II。经响应面试验优化后,表达量可以达到7.30 μg/mL。本研究为后续使用工程菌发酵生产豆血红蛋白奠定了基础。     

Microstructure and mechanical properties of (Ti,W)C cermets prepared by ultrafast spark plasma sintering

To explore the impact of the sintering rate on the microstructure and mechanical properties of cermets, the preparation of (Ti,W)C cermets by ultrafast sintering via spark plasma sintering (SPS) is reported. Compared with a slow heating rate, the electric field produced by an ultrafast heating rate enhances the liquid phase mass transfer of the metal binder phase, thus achieving rapid densification of (Ti,W)C cermets and effectively inhibiting abnormal grain growth. However, an excessive heating rate will lead to an “overflow” phenomenon, which reduces the grain growth difficulty and the bonding strength between grains. The results show that when the heating rate is 500 °C/min, the liquid phase mass transfer is moderate, the densification degree is the highest and the mechanical properties are excellent. The flexural strength, Vickers hardness and fracture toughness are 1340.90 ± 23.55 MPa, 18.42 ± 0.46 GPa and 11.96 ± 0.23 MPa?m^1/2, respectively.     

Effects of Si3N4 and WC on the oxidation resistance of ZrB2/SiC ceramic tool materials

ZrB₂/SiC, ZrB₂/SiC/Si₃N₄ and ZrB₂/SiC/WC ceramic tool materials were prepared by spark plasma sintering technology, and their oxidation resistance was tested at different oxidation temperatures. When the oxidation temperature is 1300 °C, the oxide layer thickness, oxidation weight gain and flexural strength of ZrB₂/SiC/Si₃N₄ ceramic tool material after oxidation are 8.476 μm, 1.436 mg cm^?2 and 891.0 MPa, respectively. Compared with ZrB₂/SiC ceramic tool materials, the oxide layer thickness and oxidation weight gain are reduced by 8.2% and 11.8%, respectively, and the flexural strength after oxidation is increased by 116.1%. However, the addition of WC significantly reduces the oxidation resistance of the ceramic tool material. A dense oxide film is formed on the surface of ZrB₂/SiC/Si₃N₄ ceramic tool material during oxidation, which effectively prevents oxygen from entering the inside of the material, thereby improving the oxidation resistance of the ceramic tool material.     

Lightwave irradiation-assisted low-temperature solution synthesis of indium-tin-oxide transparent conductive films

Transparent conductive oxide (TCO) films have important applications in many areas. Unfortunately, TCOs are usually fabricated using vacuum and high-temperature methods, preventing them from applications in low-cost flexible devices. In this paper, facile low-temperature sol-gel method is described that can be used to fabricate high-quality TCO films. This study uses lightwave (LW) irradiation (at ～280 °C) with indium-tin-oxide (ITO) as a typical example. Both structure and key properties of ITO films are investigated for different LW irradiation conditions. ITO can be formed via LW irradiation after a period as short as 5 min. Furthermore, it is found that LW irradiation can promote the formation of M ? O framework, effectively remove Cl impurities, and facilitate the elimination of hydroxyl oxygen defects - even at temperatures as low as ～280 °C. The optimal ITO films show excellent electronic properties, including low sheet-resistance (14.5 Ω·sq^?1) and high conductivity (1.7 × 10³ S cm^?1). Moreover, ITO films also show high transmittance (above 87%). Overall, our ITO films have a figure of merit (FOM) of 1.72 × 10^?2 Ω^?1, which is comparable to (or higher than) those of previous ITO films that were produced using conventional vacuum and high-temperature methods. Our LW irradiation method provides facile and effective approach to produce high-performance TCO films at remarkably low cost. This means these films could be used in affordable flexible large-area devices.     

基于深度学习的遥感图像道路分割

为在遥感图像中提取出来道路信息,利用深度学习技术,引入U²-Net模型进行遥感图像道路分割。相比于传统的道路提取方法,基于U²-Net方法可以实现道路的自动化提取。为验证U²-Net模型分割效果,选取U-Net、DeepLabV3+等近几年较为流行的语义分割方法进行对比试验,并进一步分析U²-Net显著图融合模块中卷积核对道路提取效果的影响。试验结果表明,U²-Net模型能较有效地提取出道路信息,模型在测试集上的平均交并比达到了76.49%,Kappa达到了0.701 2,分割精度优于U-Net、DeepLabV3+等语义分割方法。基于U²-Net模型的深度学习方法可以用于解决遥感图像中的道路分割问题,并具有较好的分割效果。     

A highly sensitive non-enzymatic glucose sensor based on CuNi nanoalloys through one-step electrodeposition strategy

Journal of Applied Electrochemistry - In this contribution, a uniformly distributed CuNi active nanoalloys was obtained on the electrode substrate by one-step facile electrodeposition method, and a...     

Physicochemical and functional properties of goat milk whey protein and casein obtained during different lactation stages

During lactation, goat milk contains colostrum, transitional milk, mature milk, and end milk. The protein present in goat milk during different lactation periods has different characteristics. This study aimed to characterize the protein profile of goat milk samples obtained at different lactation stages and to identify changes in the physicochemical and functional properties of whey protein and casein from goat milk collected at 1, 3, 15, 100, and 200 d after calving. The results demonstrated that the lactation period had a great influence on the physicochemical and functional properties of goat milk whey protein and casein, especially the protein properties of colostrum on the first day after delivery. The denaturation temperature, hydrophobicity, and turbidity of whey protein were significantly higher on the first day postpartum than at other lactation periods. Correspondingly, the colostrum whey protein also had better functional properties, such as emulsification, oil holding capacity, and foaming properties on the first day postpartum than at other lactation periods. For casein, the turbidity, particle size, water holding capacity, and foaming properties on the first day after delivery were significantly higher than those at other lactation periods, whereas the denaturation temperature, oil holding capacity, and emulsification followed the opposite trend. For both whey protein and casein, the 2 indicators of emulsifying properties, namely, emulsifying activity index and the emulsion stability, also followed an opposite trend relative to lactation stage, whereas the changes in foaming capacity with the lactation period were completely consistent with the change of foaming stability. These findings could provide useful information for the use of goat milk whey protein and casein obtained during different lactation stages in the dairy industry.     

Ionization of a polarized hydrogen atomic beam in an ECR discharge

The production of an intense beam of polarized hydrogen ions with an ECR ionizer has been investigated. A deuteron tensor polarization of up to 85% of the theoretical value has been observed. The intensity is significantly improved compared to an electron beam ionizer.     

固态发酵技术的研究应用现状

首先介绍了固态发酵的技术、特点及其优越性,并与液态发酵进行了对比;简要介绍了其最新研究状况及其在食品加工业、资源环境等各领域中的应用;描述了其发展趋势及应用前景。     

高固含低成本聚酰胺树脂合成及其应用

PAE为活性高分子树脂,固含量越高,稳定性越难控制。该文探讨了一种固含量为35%、低成本PAE的制备方法及与市售增强剂进行比较。结果表明,选择胺/酸摩尔比为1:1～1:1.05,聚酰胺预聚体反应温度为170℃左右,环氧化反应后得到黏度为50～60s的聚酰胺树脂,其干抗张强度优于市售PAE,湿抗张强度相当,保存时间为6个月。