电机驱动微装配在双光子制备微结构中的应用

对微结构的制作、微装配系统进行了研究. 采用飞秒激光双光子聚合微加工技术制作有底座、精细的三维立体“拱形”微结构, 其高250μm、长300μm、厚50μm. 将此微结构与实验室自主搭建的二维微装配平台相结合, 利用自主编程的人机交互界面驱动步进电机, 远程操控微装配设备; 将荧光闪烁陶瓷粉末装配到微结构中, 对装配后的微结构进行荧光光谱表征发现, 纯荧光粉末和微结构中的荧光粉末的发射光谱在测量误差范围内基本一致, 表明荧光粉末的光学性质未发生改变. 利用该装置可以将各类微纳米级材料和微结构进行装配, 形成含有不同材料的微结构系统.     

Feature extraction method based on NOFRFs and its application in faulty rotor system with slight misalignment

Nonlinear Dynamics - Fault features extraction method for slight misalignment of rotor systems is researched in this paper. When a rotor system with faults is excited by harmonic inputs, system...     

Promoter-Controlled Synthesis and Conformational Analysis of Cyclic Mannosides up to a 32-mer

Cyclodextrins are widely used as carriers of small molecules for drug delivery owing to their remarkable host properties and excellent biocompatibility. However, cyclic oligosaccharides with different sizes and shapes are limited. Cycloglycosylation of ultra-large bifunctional saccharide precursors is challenging due to the constrained conformational spaces. Herein we report a promoter-controlled cycloglycosylation approach for the synthesis of cyclic α-(1→6)-linked mannosides up to a 32-mer. Cycloglycosylation of the bifunctional thioglycosides and (Z)-ynenoates was found to be highly dependent on the promoters. In particular, a sufficient amount of a gold(I) complex played a key role in the proper preorganization of the ultra-large cyclic transition state, providing a cyclic 32-mer polymannoside, which represents the largest synthetic cyclic polysaccharide to date. NMR experiments and a computational study revealed that the cyclic 2-mer, 4-mer, 8-mer, 16-mer, and 32-mer mannosides adopted different conformational states and shapes.     

Sodium Carbazolide and Derivatives as Solid-State Electrolytes for Sodium-Ion Batteries

Replacing widely used organic liquid electrolytes with solid-state electrolytes (SSEs) could effectively solve the safety issues in sodium-ion batteries. Efforts on seeking novel solid-state electrolytes have been continued for decades. However, issues about SSEs still exist, such as low ionic conductivity at ambient temperature, difficulty in manufacturing, low electrochemical stability, poor compatibility with electrodes, etc. Here, sodium carbazolide (Na-CZ) and its THF-coordinated derivatives are rationally fabricated as Na⁺ conductors, and two of their crystal structures are successfully solved. Among these materials, THF-coordinated complexes exhibit fast Na⁺ conductivities, i.e., 1.20×10⁻⁴ S cm⁻¹ and 1.95×10⁻³ S cm⁻¹ at 90 °C for Na-CZ-1THF and Na-CZ-2THF, respectively, which are among the top Na⁺ conductors under the same condition. Furthermore, stable Na plating/stripping is observed even over 400 h cycling, showing outstanding interfacial stability and compatibility against Na electrode. More advantages such as ease of synthesis, low-cost, and cold pressing for molding can be obtained. In situ NMR results revealed that the evaporation of THF may play an essential role in the Na⁺ migration, where the movement of THF creates defects/vacancies and facilitates the migration of Na⁺.     

Hollow Carbon Nanofibers Filled with MnO2 Nanosheets as Efficient Sulfur Hosts for Lithium–Sulfur Batteries

Lithium–sulfur batteries have been investigated as promising electrochemical‐energy storage systems owing to their high theoretical energy density. Sulfur‐based cathodes must not only be highly conductive to enhance the utilization of sulfur, but also effectively confine polysulfides to mitigate their dissolution. A new physical and chemical entrapment strategy is based on a highly efficient sulfur host, namely hollow carbon nanofibers (HCFs) filled with MnO₂ nanosheets. Benefiting from both the HCFs and birnessite‐type MnO₂ nanosheets, the MnO₂@HCF hybrid host not only facilitates electron and ion transfer during the redox reactions, but also efficiently prevents polysulfide dissolution. With a high sulfur content of 71 wt % in the composite and an areal sulfur mass loading of 3.5 mg cm^?2 in the electrode, the MnO₂@HCF/S electrode delivered a specific capacity of 1161 mAh g^?1 (4.1 mAh cm^?2) at 0.05 C and maintained a stable cycling performance at 0.5 C over 300 cycles.     

数字图像法测定养殖水中的孔雀石绿

建立一种简单、可靠的养殖水中孔雀石绿的数字图像检测方法。以1-己基-3-甲基咪唑四氟硼酸盐离子液体富集水样品,再用手机拍照获取样品信息,最后用数字图像结合多层感知器神经网络定量分析孔雀石绿的含量。该法测定结果的相对标准偏差不大于6%(n=5),加标回收率为97.8%~103.0%。该方法可用于养殖水中孔雀石绿的含量测定。     

Label-Free Fluorescence Molecular Beacon Probes Based on G-Triplex DNA and Thioflavin T for Protein Detection

Protein detection plays an important role in biological and biomedical sciences. The immunoassay based on fluorescence labeling has good specificity but a high labeling cost. Herein, on the basis of G-triplex molecular beacon (G3MB) and thioflavin T (ThT), we developed a simple and label-free biosensor for protein detection. The biotin and streptavidin were used as model enzymes. In the presence of target streptavidin (SA), the streptavidin hybridized with G3MB-b (biotin-linked-G-triplex molecular beacon) perfectly and formed larger steric hindrance, which hindered the hydrolysis of probes by exonuclease III (Exo III). In the absence of target streptavidin, the exonuclease III successively cleaved the stem of G3MB-b and released the G-rich sequences which self-assembled into a G-triplex and subsequently activated the fluorescence signal of thioflavin T. Compared with the traditional G-quadruplex molecular beacon (G4MB), the G3MB only needed a lower dosage of exonuclease III and a shorter reaction time to reach the optimal detection performance, because the concise sequence of G-triplex was good for the molecular beacon design. Moreover, fluorescence experiment results exhibited that the G3MB-b had good sensitivity and specificity for streptavidin detection. The developed label-free biosensor provides a valuable and general platform for protein detection.     

Microalgae separation by inertia-enhanced pinched flow fractionation

To improve the accuracy and efficiency of ships’ ballast water detection, the separation of microalgae according to size is significant. In this article, a method to separate microalgae based on inertia-enhanced pinched flow fractionation (iPFF) was reported. The method utilized the inertial lift force induced by flow to separate microalgae according to size continuously. The experimental results show that, as the Reynolds number increases, the separation effect becomes better at first, but then stays unchanged. The best separation effect can be obtained when the Reynolds number is 12.3. In addition, with the increase of the flow rate ratio between sheath fluid and microalgae mixture, the separation effect becomes better and the best separation effect can be obtained when the flow rate ratio reaches 10. In this case, the recovery rate of Tetraselmis sp. is about 90%, and the purity is about 86%; the recovery rate of Chlorella sp. is as high as 99%, and the purity is about 99%. After that, the separation effect keeps getting better but very slowly. In general, this study provides a simple method for the separation of microalgae with different sizes, and lays a foundation for the accurate detection of microalgae in the ballast water.     

Evaluating a four-directional benzene-centered aliphatic polyamine curing agent for epoxy resins

A four-directional benzene-centered aliphatic polyamine, MXBDP, with high functionality and low volatility, is used to cure epoxy resin (DGEBA). Herein we originally report the isothermal cure kinetics and dynamic mechanical properties of DGEBA/MXBDP. Differential scanning calorimetry confirms that MXDBP is more reactive than commercial linear metaxylenediamine and branched Jeffamine T-403 and the isothermal curing reaction is autocatalytic. The Kamal model is found to be able to well describe the curing rate up to the onset of diffusion control, and the excellent match over the whole conversion range is achieved using the extended Kamal model. Interestingly, the isoconversional kinetic analysis indicates that the effective reaction activation energy (E _α ) changes substantially with conversion, and ultimately decreases to a very small value (<10 kJ mol^?1) because of the diffusion-controlled reaction kinetics. Then, dynamic mechanical analysis reveals that DGEBA/MXBDP exhibits the higher α- and β-relaxation temperatures and the much higher crosslink density than DGEBA/metaxylenediamine. Our experiment results support that MXBDP has the high reactivity and improved thermal resistance in combination with the advantages of the high functionality, low volatility and decreased CO₂ absorption. Therefore, MXBDP may be especially suitable for room temperature-cure epoxy coatings and adhesives.     

大学物理教学改革实践浅析——“问题导向”式学习的意义及应用

针对当前我国高校大学物理教学中存在诸多问题的现状,提出"问题导向"式教学的解决途径."问题导向"学习中"教"与"学"的方式有较大跨度的转变,它以学生为中心,以问题为导向,其中问题的设置环节对师生良好互动的实现至关重要.文章就振动内容问题的设计和提出进行简单应用尝试,以期为后续大学物理教学改革的持续进行提供帮助.