金属Ta缓冲层上生长微晶Si薄膜的结晶性研究

利用射频磁控溅射技术,在生长了Ta缓冲层的石英玻璃衬底上采用不同溅射功率下制备了一系列的硅薄膜样品,用拉曼光谱和X射线衍射表征了薄膜的结晶性随溅射功率的变化情况.实验结果表明:随着溅射功率的增加,薄膜逐渐由非晶向微晶过渡,晶粒沿Si(311)面呈柱状生长,功率升高到80 W时薄膜的晶化率达到75.4;,薄膜为典型的微晶结构.继续增加功率,薄膜的结晶性变差,晶化率下降,在60～120 W之间存在一个优化理想的射频溅射功率,在此功率下生长的薄膜样品的结晶性最高.本文还尝试解释了Ta缓冲层在Si晶化过程中的作用.     

超声电铸提高金属微流控芯片模具的均匀性

利用微电铸技术制作的微流控芯片模具往往存在沉积厚度不均匀的缺陷,这种缺陷会影响模具的尺寸精度及使用性能,并增加模具的制作成本。为了制得厚度均匀的微流控芯片模具,研究了超声电铸对模具均匀性的影响。首先,采用有限元软件COMSOL Multiphysics建立微流控芯片模具的微电铸模型,分析电铸2 h后的模具的厚度分布。并根据该仿真结果,设计掩模版。然后,在自主搭建的超声电铸装置中进行一系列电铸实验,来研究超声搅拌对模具均匀性的影响。实验结果表明：电铸过程中添加超声搅拌可以改善微流控芯片模具的均匀性。超声功率为200 W时,超声频率改善模具均匀性的程度为200 kHz＞80 kHz＞120 kHz。超声频率为200 kHz时,超声功率改善模具均匀性的程度为500 W＞200 W＞100 W。当超声的频率和功率分别为200 kHz和500 W时,与无超声电铸相比,模具的均匀性提高约30%。     

探地雷达超宽带高斯脉冲信号源的设计

脉冲源作为探地雷达的核心部件,其高功率和超宽频带可保证探测距离和探测分辨率,波形的光滑性与稳定性同时也影响着目标成像质量。选用雪崩三极管组成Marx电路输出单极性脉冲,采取措施优化波形中的不光滑部分,精确计算传输线延迟时间,信号反向叠加形成双极性脉冲,设计梳状PCB形式有利于脉冲源的小型化。测量结果表明：脉冲波形平滑对称,正负峰间脉宽为1.64 ns,幅度为812 V(50 负载),拖尾振荡低于总体幅值的10%,和仿真结果吻合较好,符合探地雷达的需求。     

侧面泵浦主振荡功率放大器中的光束质量提高

报道了一种利用球差补偿效应提高侧面泵浦主振荡功率放大器输出光束质量的实验装置。在理论上提出了一种新的球差补偿方法,利用正球差经过会聚透镜焦点后向负球差转化的现象,补偿下一放大级中的正球差效应。在实验上搭建了两级放大的侧面泵浦Nd:YAG主振荡功率放大器。在连续输出的情况下,从振荡级输出功率为42 W、光束质量因子为1.48的种子光,经过一级放大后的功率为74 W,光束质量因子恶化为1.80;继续经过二级放大后,光束质量因子提高为1.40。实验结果表明,所提出的球差补偿理论是提高激光放大过程中光束质量的有效手段。     

Neuroprotective Effect of Ginseng Fibrous Root Enzymatic Hydrolysate against Oxidative Stress

Oxidative stress is one of the potential causes of nervous system disease. Ginseng extract possesses excellent antioxidant activity; however, little research on the function of the ginseng fibrous root. This study aimed to investigate the neuroprotective effects of ginseng fibrous root to alleviate the pathogenesis of Alzheimer’s disease (AD) against oxidative stress. Ginseng fibrous root enzymatic hydrolysate (GFREH) was first prepared by digesting ginseng fibrous roots with alkaline protease. In vitro, the GFREH showed antioxidant activities in free radical scavenging mechanisms. With a cellular model of AD, GFREH inhibited the increase in Ca²⁺ levels and intracellular ROS content, maintained the balance of mitochondrial membrane potential, and relieved L-glutamic acid-induced neurotoxicity. In vivo, GFREH improved the survival rate of Caenorhabditis elegans (C. elegans) under oxidative stress, upregulated SOD-3 expression, and reduced reactive oxygen species (ROS) content. Therefore, our findings provide evidence for the alleviation effect of GFREH against oxidative stress in neuroprotection, which may accelerate the development of anti-Alzheimer’s drugs and treatments in the future.     

Trimodal hierarchical porous carbon nanorods enable high-performance Na–Se batteries

Technical bottlenecks of polyselenide shuttling and material volume variation significantly hamper the development of emerging sodium–selenium (Na–Se) batteries. The nanopore structure of substrate materials is demonstrated to play a vital role in stabilizing Se cathodes and approaching superior Na-ion storage properties. Herein, an ideal nanorod-like trimodal hierarchical porous carbon (THPC) host is fabricated through a facile one-step carbonization method for advanced Na–Se batteries. The THPC possesses a trimodal nanopore structure encompassing micropores, mesopores, and macropores, and functions as a good accommodator of Se molecules, a reservoir of polyselenide intermediates, a buffer for volume expansion of Se species during sodiation, and a promoter for electron/ion transfer in the electrochemical process. As a result, Na–Se batteries assembled with the Se–THPC composite cathode realize high utilization of Se, fast redox kinetics, and excellent cyclability. Furthermore, the Na-ion storage mechanism of the well-designed Se–THPC composite is profoundly revealed by in situ visual characterization techniques.

Technical bottlenecks of polyselenide shuttling and material volume variation significantly hamper the development of emerging sodium–selenium (Na–Se) batteries.     

The Influence of Ions on the Electrochemical Stability of Aqueous Electrolytes

The electrochemical stability window of water is known to vary with the type and concentration of dissolved salts. However, the underlying influence of ions on the thermodynamic stability of aqueous solutions has not been fully understood. Here, we investigated the electrolytic behaviors of aqueous electrolytes as a function of different ions. Our findings indicate that ions with high ionic potentials, i.e., charge density, promote the formation of their respective hydration structures, enhancing electrolytic reactions via an inductive effect, particularly for small cations. Conversely, ions with lower ionic potentials increase the proportion of free water molecules—those not engaged in hydration shells or hydrogen-bonding networks—leading to greater electrolytic stability. Furthermore, we observe that the chemical environment created by bulky ions with lower ionic potentials impedes electrolytic reactions by frustrating the solvation of protons and hydroxide ions, the products of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. We found that the solvation of protons plays a more substantial role than that of hydroxide, which explains a greater shift for OER than for HER, a puzzle that cannot be rationalized by the notion of varying O−H bond strengths of water. These insights will help the design of aqueous systems.     

高空电磁脉冲作用下电力系统主要效应模式分析

随着电网智能化和整体规模的提高,现代电力系统越来越容易受到高空电磁脉冲的威胁,一旦关键环节故障将有可能导致连锁反应,造成大面积停电。而针对不同的电力设备,其效应模式和威胁等级也有所不同,需要进行分类和分级研究。根据电力设备在电磁脉冲作用下的不同效应模式,将其分为SCADA系统与继电保护设备,变压器、互感器等线圈类设备,线路与设备避雷器与其他设备,并分析了其效应机理。然后考虑高空电磁脉冲威胁下电力设备存在多种效应等级,介绍了不同效应分类方法以及多等级效应评估模型。最后综合考虑易损性和重要性以及系统间的级联影响,分别梳理总结了在E1和E3作用下电力系统的故障链模式。     

高效液相色谱-串联质谱法测定盐酸二甲双胍及其制剂中痕量N-亚硝基二甲胺

建立了高效液相色谱-串联质谱(HPLC-MS/MS)检测盐酸二甲双胍原料和制剂中N-亚硝基二甲胺(NDMA)含量的方法。样品以水为提取溶剂,经涡旋混匀、恒温振荡、高速离心、微孔过滤后进行HPLC-MS/MS分析。采用ACE EXCEL 3 C18-AR色谱柱(150 mm×4.6 mm, 3μm)分离,流动相为均含0.1%甲酸的水和甲醇溶液,梯度洗脱,流速0.8 mL/min,柱温40℃,自动进样器温度10℃。采用阀切换技术保护质谱仪,设置六通阀切换使保留时间2.85～7.00 min的流动相进入质谱,其余时间流动相进入废液。质谱部分采用大气压化学电离(APCI)源,在正离子、MRM模式下扫描,雾化器流量为3 L/min,加热器流量为10 L/min,接口温度为300℃,脱溶剂管温度为250℃,加热块温度为400℃,干燥器流量为10 L/min。NDMA定量离子对为m/z 75.0→43.1,碰撞能量(CE)为-17.0 eV,定性离子对为m/z 75.0→58.2, CE为-16.0 eV。采用外标法定量。对方法进行了详细的方法学验证,结果表明,该法专属性良好,溶剂和辅料对NDMA测...     

一种宽吻海豚通讯信号自动分类的方法

针对宽吻海豚通讯信号自动分类提出了一种基于句法模式识别的方法。该方法首先提取海豚通讯信号基频随时间变化的轨迹曲线,然后提取基频变化的基元序列。根据海豚通讯信号分类的标准,归纳出产生各类海豚通讯信号基频基元序列的文法。对未知类别的海豚通讯信号,提取其基频变化的基元序列,根据各类模式的文法对基元序列进行分类,进而实现海豚通讯信号的自动分类。实验结果显示本文方法的分类准确率达到了95%。本文方法预期为海豚生物学行为的声学研究提供一定的技术支持。