磺化嵌段型共聚物在质子交换膜燃料电池中的应用

燃料电池是以碳氢化合物为燃料的一种新型、清洁的发电装置,而其中的质子交换膜燃料电池由于具有可快速启动的优点而可应用于机动车等领域。所用的质子交换膜需要具有高的质子传导性、低的甲醇/水渗透性、好的机械和热稳定性以及合适的价格等特点,但目前已经工业化的Nafion膜并未能全部满足上述要求。为了解决这些问题,目前已经开发了多种新的质子交换膜。本文对其中的磺化嵌段型聚醚砜、磺化嵌段型聚酰亚胺和苯乙烯基嵌段共聚物在质子交换膜燃料电池中的应用进行了综述,并与Nafion膜和相应的无规共聚物的性能进行了比较。最后展望了嵌段共聚物在质子交换膜领域的发展趋势。     

DA-LSTM-VAE: Dual-Stage Attention-Based LSTM-VAE for KPI Anomaly Detection

To ensure the normal operation of the system, the enterprise’s operations engineer will monitor the system through the KPI (key performance indicator). For example, web page visits, server memory utilization, etc. KPI anomaly detection is a core technology, which is of great significance for rapid fault detection and repair. This paper proposes a novel dual-stage attention-based LSTM-VAE (DA-LSTM-VAE) model for KPI anomaly detection. Firstly, in order to capture time correlation in KPI data, long–short-term memory (LSTM) units are used to replace traditional neurons in the variational autoencoder (VAE). Then, in order to improve the effect of KPI anomaly detection, an attention mechanism is introduced into the input stage of the encoder and decoder, respectively. During the input stage of the encoder, a time attention mechanism is adopted to assign different weights to different time points, which can adaptively select important input sequences to avoid the influence of noise in the data. During the input stage of the decoder, a feature attention mechanism is adopted to adaptively select important latent variable representations, which can capture the long-term dependence of time series better. In addition, this paper proposes an adaptive threshold method based on anomaly scores measured by reconstruction probability, which can minimize false positives and false negatives and avoid adjustment of the threshold manually. Experimental results in a public dataset show that the proposed method in this paper outperforms other baseline methods.     

The Anisotropic Chemical Reaction Mechanism of 1,3,3-trinitroazetidine (TNAZ) under Different Shock Wave Directions by ReaxFF Reactive Molecular Dynamics Simulations

1,3,3-Trinitroazetidine (TNAZ) has good thermal stability and low shock sensitivity, among other properties, and it has broad prospects in insensitive ammunition applications. In this study, a molecular dynamics calculation based on the ReaxFF-lg force field and multiscale shock technique (MSST) was used to simulate the shock-induced chemical reaction of TNAZ with different shock wave directions. The results showed that the shock sensitivity of TNAZ was in the order of [100] > [010] > [001]. There were significant differences in molecular arrangements in different shock directions, which affected the reaction rate and reaction path in different directions. The molecular arrangement in the [010] and [001] directions formed a “buffer” effect. The formation and cleavage of bonds, formation of small molecules and growth of clusters were analyzed to show the effect of the “buffer”. The polymerization reactions in the [010] and [001] directions appeared later than that in the [100] direction, and the cluster growth in the [010] and [001] directions was slower than that in the [100] direction. In different shock loading directions, the formation and cleavage mechanisms of the N-O bonds of the TNAZ molecules were different, which resulted in differences in the initial reaction path and reaction rate in the three directions     

Radical-Induced Cascade Annulation/Hydrocarbonylation for Construction of 2-Aryl-4H-chromen-4-ones

A robust metal- and solvent-free cascade radical-induced C-N cleavage/intramolecular 6-endo-dig annulation/hydrocarbonylation for the synthesis of the valuable 2-aryl-4H-chromen-4-ones is described. This practical synthesis strategy utilizes propargylamines and air as the oxygen source and green carbonylation reagent, in which propargylamines are activated by the inexpensive and available dimethyl 2,2′-azobis(2-methylpropionate) (AIBME) and (PhSe)₂ as the radical initiators. This simple and green protocol features wide substrate adaptability, good functional group tolerance, and amenability to scaling up and derivatizations.     

基于能量变化的微尺度金属应变突变准则研究

微尺度金属在塑性变形过程中呈现出显著的应变突变特性.论文以力加载条件下单晶Ni微米柱体和位移加载下Au纳米柱体为对象,探讨应变突变的判定准则与不同特征阶段的判别条件.首先从经典塑性理论Hill稳定性条件出发,分析微柱体变形过程中的动能变化,提出了应变突变发生与结束的判定准则.进一步分析柱体变形过程中的内能变化,结合动能变化的分析结果,给出了微尺度金属不同变形阶段的判别条件.通过与文献中实验与理论结果对比发现,基于动能变化的应变突变判定准则能够判断应变突变的发生与结束,基于能量变化的判别条件可以有效区分微柱体的不同变形阶段.最后对新理论准则的可靠性与适用性进行了讨论.     

Solid Sampling Pyrolysis Adsorption-Desorption Thermal Conductivity Method for Rapid and Simultaneous Detection of N and S in Seafood

In this work, a rapid method for the simultaneous determination of N and S in seafood was established based on a solid sampling absorption-desorption system coupled with a thermal conductivity detector. This setup mainly includes a solid sampling system, a gas line unit for controlling high-purity oxygen and helium, a combustion and reduction furnace, a purification column system for moisture, halogen, SO₂, and CO₂, and a thermal conductivity detector. After two stages of purging with 20 s of He sweeping (250 mL/min), N₂ residue in the sample-containing chamber can be reduced to <0.01% to improve the device’s analytical sensitivity and precision. Herein, 100 s of heating at 900 °C was chosen as the optimized decomposition condition. After the generated SO₂, H₂O, and CO₂ were absorbed by the adsorption column in turn, the purification process executed the vaporization of the N-containing analyte, and then N₂ was detected by the thermal conductivity cell for the quantification of N. Subsequently, the adsorbed SO₂ was released after heating the SO₂ adsorption column and then transported to the thermal conductivity cell for the detection and quantification of S. After the instrumental optimization, the linear range was 2.0–100 mg and the correlation coefficient (R) was more than 0.999. The limit of detection (LOD) for N was 0.66 μg and the R was less than 4.0%, while the recovery rate ranged from 95.33 to 102.8%. At the same time, the LOD for S was 2.29 μg and the R was less than 6.0%, while the recovery rate ranged from 92.26 to 105.5%. The method was validated using certified reference materials (CRMs) and the measured N and S concentrations agreed with the certified values. The method indicated good accuracy and precision for the simultaneous detection of N and S in seafood samples. The total time of analysis was less than 6 min without the sample preparation process, fulfilling the fast detection of N and S in seafood. The establishment of this method filled the blank space in the area of the simultaneous and rapid determination of N and S in aquatic product solids. Thus, it provided technical support effectively to the requirements of risk assessment and detection in cases where supervision inspection was time-dependent.     

弱谐波情况下透射光栅衍射效率标定方法

同步辐射光源中的高次谐波会使透射光栅衍射效率标定精度变差。为了校正光源中的高次谐波对透射光栅衍射效率标定的影响,提出了一种光源存在弱谐波情况下的透射光栅衍射效率标定方法,通过使用谐波X射线的衍射效率修正基波衍射效率标定中谐波的影响,从而得到更为准确的透射光栅衍射效率。使用该标定方法在北京同步辐射光源上开展了透射光栅相对衍射效率标定工作。实验结果表明：在100~800 eV存在高次谐波能段,修正后透射光栅一级与零级的相对衍射效率与理论模拟结果吻合较好,修正后光栅二级与一级的相对衍射效率更接近理论模拟结果,但与理论模拟结果仍有较大偏差,该偏差主要来源光栅较弱的二级衍射。     

气体火花开关电极烧蚀研究

采用Mo,WCu和W分别作为三种气体火花开关的主电极材料,进行放电条件下电极烧蚀实验,研究开关电极烧蚀率和烧蚀形貌,分析电极烧蚀特征。结果表明,Mo,WCu和W开关的主电极烧蚀率分别为3.3210-2 C-1m-2, 2.6310-2 C-1m-2和1.710-2 C-1m-2,W开关主电极烧蚀率最小。实验后开关的主电极中心烧蚀严重,呈现明显裂纹和烧蚀坑。Mo主电极表面呈现明显熔融态,阴极表面形成大量裂纹（宽度达10 m）和孔隙（孔径达10 m）;WCu和W主电极表面形成少量圆球状W突起（粒径达20 m及以上）。开关外壳内壁沉积了喷溅颗粒。WCu开关外壳沉积颗粒较大（粒径达10 m）,Mo开关外壳沉积颗粒居中（粒径为2 m）,W开关外壳沉积颗粒最小（近1 m）。因此可优先选用具有优异抗烧蚀性能的W作为气体火花开关电极材料。     

The Pharmacokinetics in Mice and Cell Uptake of Thymus Immunosuppressive Pentapeptide Using LC-MS/MS Analysis

Thymus immunosuppressive pentapeptide (TIPP) is a novel anti-inflammatory peptide with high efficacy and low toxicity. This study aims to establish a selective LC-MS/MS method for analyzing the analyte TIPP in biological samples, laying the foundation for further PK and PD studies of TIPP. Protein precipitation was conducted in acetonitrile supplemented with 2% formic acid and 25 mg/mL dithiothreitol as a stabilizer, which was followed by backwashing the organic phase using dichloromethane. The chromatographic separation of TIPP was achieved on a C18 column with a gradient elution method. During positive electrospray ionization, TIPP was analyzed via multiple-reaction monitoring. The linear relationships between the concentration of TIPP and peak area in murine plasma cell lysates, supernatants, and the final cell rinse PBS were established within the ranges of 20–5000 ng/mL, 1–200 ng/mL, 10–200 μg/mL, and 0.1–20 ng/mL, respectively (r² > 0.99). Validated according to U.S. FDA guidelines, the proposed method was proved to be acceptable. Such a method had been successfully applied to investigate the pharmacokinetics of TIPP in mice via subcutaneous injection. The plasma half-life in mice was 5.987 ± 1.824 min, suggesting that TIPP is swiftly eliminated in vivo. The amount of TIPP uptake by RBL-2H3 cells was determined using this method, which was also visually verified by confocal. Furthermore, the effective intracellular concentration of TIPP was deduced by comparing the intracellular concentration of TIPP and degrees of inflammation, enlightening further investigation on the intracellular target and mechanism of TIPP.     

Vinyl Groups Containing Tetraphenylethylene Derivatives as Fluorescent Probes Specific for Palladium and the Quenching Mechanism

Main observation and conclusion We previously reported that a series of tetraphenylethylene(TPE)-containing all-hydrocarbon conjugated polymers exhibited a spe-...