磁场效应对理解水分解反应物的可能意义

电催化水分解由两个基元反应构成,即析氢反应(HER)和析氧反应(OER).开发强大的HER和OER技术需要在分子层面理解反应机理,然而,目前水分解反应的反应物还没有完全确定.本文利用磁场来研究HER中的质子传输和OER中的氢离子传输,对确定HER和OER中真实的反应物具有重要意义.磁场是改变离子等带电物质运动的一种有效...     

Comparative Study on Preparation Methods for Transparent Conductive Films Based on Silver Nanowires

Silver nanowires, which have high optoelectronic properties, have the potential to supersede indium tin oxide in the field of electrocatalysis, stretchable electronic, and solar cells. Herein, four mainstream experimental methods, including Mayer–rod coating, spin coating, spray coating, and vacuum filtration methods, are employed to fabricate transparent conductive films based on the same silver nanowires to clarify the significance of preparation methods on the performance of the films. The surface morphology, conductive property, uniformity, and flexible stability of these four Ag NW-based films, are analyzed and compared to explore the advantages of these methods. The transparent conductive films produced by the vacuum filtration method have the most outstanding performance in terms of surface roughness and uniformity, benefitting from the stronger welding of NW-NW junctions after the press procedure. However, limited by the size of the membrane and the vacuum degree of the equipment, the small-size Ag films used in precious devices are appropriate to obtain through this method. Similarly, the spin coating method is suited to prepare Ag NWs films with small sizes, which shows excellent stability after the bending test. In comparison, much larger-size films could be obtained through Mayer-rod coating and spray coating methods. The pull-down speed and force among the Mayer-rod coating process, as well as the spray distance and traveling speed among the spray coating process, are essential to the uniformity of Ag NW films. After being treated with NaBH₄ and polymethyl methacrylate (PMMA), the obtained Ag NW/PMMA films show great potential in the field of film defogging due to the Joule heating effect. Taken together, based on the advantages of each preparation method, the Ag NW-based films with desired size and performances are easier to prepare, meeting the requirements of different application fields.     

Efficient Degradation of Tetracycline Antibiotics by Engineered Myoglobin with High Peroxidase Activity

Tetracyclines are one class of widely used antibiotics. Meanwhile, due to abuse and improper disposal, they are often detected in wastewater, which causes a series of environmental problems and poses a threat to human health and safety. As an efficient and environmentally friendly method, enzymatic catalysis has attracted much attention. In previous studies, we have designed an efficient peroxidase (F43Y/P88W/F138W Mb, termed YWW Mb) based on the protein scaffold of myoglobin (Mb), an O₂ carrier, by modifying the heme active center and introducing two Trp residues. In this study, we further applied it to degrade the tetracycline antibiotics. Both UV-Vis and HPLC studies showed that the triple mutant YWW Mb was able to catalyze the degradation of tetracycline, oxytetracycline, doxycycline, and chlortetracycline effectively, with a degradation rate of ~100%, ~98%, ~94%, and ~90%, respectively, within 5 min by using H₂O₂ as an oxidant. These activities are much higher than those of wild-type Mb and other heme enzymes such as manganese peroxidase. As further analyzed by UPLC-ESI-MS, we identified multiple degradation products and thus proposed possible degradation mechanisms. In addition, the toxicity of the products was analyzed by using in vitro antibacterial experiments of E. coli. Therefore, this study indicates that the engineered heme enzyme has potential applications for environmental remediation by degradation of tetracycline antibiotics.     

Natural Antioxidants,Tyrosinase and Acetylcholinesterase Inhibitors from Cercis glabra Leaves

Cercis glabra is a plant belonging to the legume family, whose flowers and barks are commonly used as food and traditional Chinese medicines. However, its leaves are usually disposed of as wastes. This research comprehensively investigated the bioactive constituents of C. glabra leaves, and two new phenolic, ceroffesters A-B (1–2) and thirteen known compounds (3–15) were isolated. Their structures were elucidated by spectroscopic methods such as nuclear magnetic resonance (1D NMR and 2D NMR), high-resolution electrospray ionization mass spectra (HR-ESI-MS), optical rotatory dispersion (ORD) and electronic circular dichroism (ECD). All of them were assessed for their antioxidant activities through ABTS, DPPH and PTIO methodologies, and evaluated for inhibitory activities against two enzymes (mushroom tyrosinase and acetylcholinesterase). As a result, compounds 3–6, 10 and 13 exhibited evident antioxidant activities. Meanwhile, compounds 5, 10 and 13 showed the most potent tyrosinase inhibitory activities, with IC₅₀ of 0.64, 0.65 and 0.59 mM, and compared with the positive control of 0.63 mM (kojic acid). In the initial concentration of 1 mg/mL, compounds 3, 5 and 6 demonstrated moderate inhibitory activities against acetylcholinesterase with 85.27 ± 0.06%, 83.65 ± 0.48% and 82.21 ± 0.09%, respectively, compared with the positive control of 91.17 ± 0.23% (donepezil). These bioactive components could be promising antioxidants, tyrosinase and acetylcholinesterase inhibitors.     

The Role of Taraxacum mongolicum in a Puccinellia tenuiflora Community under Saline–Alkali Stress

Coexisting salt and alkaline stresses seriously threaten plant survival. Most studies have focused on halophytes; however, knowledge on how plants defend against saline–alkali stress is limited. This study investigated the role of Taraxacum mongolicum in a Puccinellia tenuiflora community under environmental saline–alkali stress to analyse the response of elements and metabolites in T. mongolicum, using P. tenuiflora as a control. The results show that the macroelements Ca and Mg are significantly accumulated in the aboveground parts (particularly in the stem) of T. mongolicum. Microelements B and Mo are also accumulated in T. mongolicum. Microelement B can adjust the transformation of sugars, and Mo contributes to the improvement in nitrogen metabolism. Furthermore, the metabolomic results demonstrate that T. mongolicum leads to decreased sugar accumulation and increased amounts of amino acids and organic acids to help plants resist saline–alkali stress. The resource allocation of carbon (sugar) and nitrogen (amino acids) results in the accumulation of only a few phenolic metabolites (i.e., petunidin, chlorogenic acid, and quercetin-3-O-rhamnoside) in T. mongolicum. These phenolic metabolites help to scavenge excess reactive oxygen species. Our study primarily helps in understanding the contribution of T. mongolicum in P. tenuiflora communities on coping with saline–alkali stress.     

5 MA 100 ns重频LTD驱动器设计

设计了用于Z箍缩丝阵实验的重频LTD驱动器, 含6路并联模组, 每组由8个0.8 MA原型模块串联组成, 全真空结构。原型模块采用全新的单路触发和电感隔离技术, 触发难度和重频运行可靠性得到显著优化。利用电路模拟程序对驱动器进行了仿真计算, 结果表明：在初始半径1.2 cm、线质量1 mg/cm的Z箍缩负载上, 驱动器的输出电流峰值可到5.2 MA, 前沿91 ns;负载内爆最大动能78 kJ, 从电容储能至负载动能的转化效率为11.7%。该驱动器预期将获得高达20%~30%的辐射能量效率, 可为Z箍缩物理研究提供高效的实验平台。     

基于Tesla变压器和Blumlein线的低抖动重频脉冲发生器

为实现MV级多级气体开关精确触发控制, 提出了基于Tesla变压器和Blumlein线的低抖动重频脉冲发生器的电触发方案。完成了Tesla变压器与Blumlein线一体化设计;优化了初级回路结构及绝缘栅双极型晶体管触发控制电路, 减小了初级杂散电感, 缩短了变压器次级高电压建立时间及时延抖动;优化了百kV级自击穿气体开关工作参数, 研制出一套多级低抖动电晕稳定开关;将传统Blumlein线绝缘介质由变压器油更换成高介电常数的MIDEL7131新油, 增加了输出脉冲宽度, 进一步提高触发能力。最终研制出一台输出电压130 kV、脉冲宽度大于5 ns、重复频率50 Hz、连续工作时间1 min、输出抖动小于10 ns的紧凑型脉冲发生器。     

金属超材料TEM-TE11高功率微波模式转换器

利用高折射率的金属超材料作为移相器,设计了一种紧凑型高功率微波TEM-TE11模式转换器。通过研究同轴扇形金属栅格超材料的传输特性,得到高折射率的全金属超材料。采用CST Microwave Studio 软件对金属超材料TEM-TE11模式转换器进行了数值模拟,结果显示：该转换器在1.56 GHz附近转换效率大于96%,相对带宽约4%,功率容量不低于2 GW,系统纵向长度仅0.42个波长。将所设计的模式转换器结合L波段磁绝缘线振荡器开展了一体化设计,在器件输出口得到了TE11模高功率微波输出。     

中国散裂中子源直线射频功率源系统的研制

中国散裂中子源加速器质子束流加速能量为1.6 GeV,重复频率为25 Hz,撞击固体金属靶产生散射中子,一期工程的打靶束流功率为100 kW。直线加速器的设计束流流强为15 mA,输出能量为81 MeV。射频加速和聚束系统包括一台射频四极场加速器、中能束流传输线的两个聚束器、四节漂移管直线加速器加速腔和直线-环束流传输线的一个散束器,与之相对应,共有8个单元在线运行的射频功率源为其提供所需的射频功率。目前,直线射频功率源系统预研项目已全部完成,各项性能参数均已达到设计指标,当前正处在批产安装调试阶段。151013     

土中爆炸成腔问题中确定炸点状态的一种计算反求方法

提出了一种通过给定的土中爆炸成腔毁伤效应确定炸点状态的计算反求方法。该方法将确定炸点状态的反问题转化为求解爆炸毁伤效应的计算值与给定值误差函数最小的优化问题。在反求过程中,采用基于误差减小比率技术的多项式近似模型代替土中爆炸数值分析模型,以便提高反求效率。采用Tikhonov正则化方法克服反求过程中出现的病态问题。在此基础上,引入信赖域管理策略判断当前近似模型与实际模型的逼近程度,以确定最优的反求向量。炸点状态反求结果与实验结果的对比分析表明,该方法能够有效且稳定地通过给定的毁伤效应实现炸点状态的反求,这可为炸点状态的设计提供参考。