模拟器电磁场与实际电磁场耦合响应等效计算

辐射波模拟器产生的脉冲电磁环境能够近似模拟高空核爆电磁脉冲（HEMP）的自由场, 然而在实际HEMP威胁环境中, 施加在地面设备上的电磁场是电磁脉冲入射波与地面反射波的合成场。通过计算不同入射情况下, HEMP自由辐射场经损耗地面反射叠加形成的总电场, 对比其与初始入射场的强度及波形变化, 分析了地面附近合成电磁场的特点。提出一种将模拟环境效应与实际环境效应进行等效转换的计算方法, 应用该方法计算了入射波电场45极化情况下的模拟环境效应修正因子。分析计算结果, 建议在开展HEMP效应的辐射波模拟试验中, 应将受试设备放在至少三个相互正交的方向上进行测试, 同时适当减小模拟器产生电磁脉冲的宽度。     

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。     

控制器组件γ瞬时辐射效应研究

瞬时电离辐射在电子器件内部形成的光电流可引起器件输出扰动,导致电路中部分器件受电源、输入信号及自身产生光电流扰动的多重影响,而单独对器件进行试验无法反映瞬时辐射输出扰动在电子组件系统中的传递影响。为此对由DC/DC、稳压器、单片机CPU,FPGA等组成的控制器组件在2.8105~1.7107 Gy(Si)/s的范围内开展了瞬时辐射效应的试验研究。试验中对组件功能和器件参数的测试结果表明,在较小的瞬时剂量率下,部分器件输出受到影响,但组件功能正常;较大剂量率时,所有器件均受影响,且组件功能中断。同时观测到瞬时辐射形成的扰动信号在器件间传输现象。     

水中脉冲放电金属电极烧蚀机理

采用板-板电极, 在放电间隙距离为2 mm、放电电流峰值为22 kA条件下, 对黄铜、钨铜电极的烧蚀特性进行了对比研究。利用高精度天平测量放电过程中的电极质量损失, 分别获取了阴极、阳极及总的平均烧蚀速率。通过放电后电极表面微观形貌、微观元素组成的分析及液体中金属离子的含量分析, 对水中脉冲放电金属电极的烧蚀机理进行了探讨。结果表明, 水中脉冲放电时, 钨铜电极的抗烧蚀性能明显高于黄铜电极。黄铜电极的主要烧蚀是以中心的大量孔洞及其边缘的波纹结构为表现形式的液体金属的溅射;钨铜电极的突出物及较平整的表面暗示了气相侵蚀的作用。以电弧的焦耳热效应为催化剂, 钨铜与水的电化学反应更为强烈, 因此电化学腐蚀是水中放电电极烧蚀的形式之一。     

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。