Xe54+离子与Xe原子碰撞过程中的辐射电子俘获及退激发辐射的理论研究

基于多组态Dirac-Fock理论方法和冲量近似, 对Xe⁵⁴⁺与Xe在197 MeV/u碰撞能量下, 炮弹离子的俘获及退激发过程进行了理论研究. 计算了炮弹离子从中性靶原子俘获一个电子到nl (n=1, 2, 3, 4, 5; l=s, p, d) 轨道上的辐射电子俘获截面和相应的辐射光子能量, 以及俘获末态退激发辐射跃迁的能量和概率. 结合这些计算结果, 进一步模拟了碰撞产生的炮弹离子的退激发X射线谱的结构, 并与兰州重离子加速器装置上的最新实验观测结果进行了比较, 符合得很好.     

Experimental Realization of an Intrinsic Magnetic Topological Insulator

An intrinsic magnetic topological insulator(TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi_2Te_4, by alternate growth of a Bi_2Te_3 quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way.     

食品中合成色素快速检测仪器的研制

基于人工合成色素在可见光区的光吸收及偏最小二乘变量筛选法,研制出合成色素速测仪器,并应用于饮料、糖果、果冻、调色酒等食品中合成色素的快速检测.速测仪具有便携、功耗低、操作简便、检测时间短并可同时对多种人工合成色素进行实时现场快速检测、检测结果准确等优点.对样品中5种食用合成色素柠檬黄、日落黄、胭脂红、苋菜红和亮蓝的检测...     

柱前衍生-反相高效液相色谱测定牛磺罗定及固体制剂含量

本文建立了对甲苯磺酰氯柱前衍生-反相高效液相色谱紫外检测法测定牛磺罗定及其固体制剂含量的方法.利用牛磺罗定中含有仲胺基的特点,以对甲基苯磺酰氯柱前衍生牛磺罗定,Venusil XBP C18色谱柱分离,在240 nm波长检测,线性范围为0.016～0.160 g·L-1(r=0.9995),衍生化产物在24 h内稳定,...     

Ultra-low on-resistance high voltage (>600 V) SOI MOSFET with a reduced cell pitch

A low specific on-resistance (R S,on) silicon-on-insulator (SOI) trench MOSFET (metal-oxide-semiconductor-field-effect-transistor) with a reduced cell pitch is proposed.The lateral MOSFET features multiple trenches:two oxide trenches in the drift region and a trench gate extended to the buried oxide (BOX) (SOI MT MOSFET).Firstly,the oxide trenches increase the average electric field strength along the x direction due to lower permittivity of oxide compared with that of Si;secondly,the oxide trenches cause multiple-directional depletion,which improves the electric field distribution and enhances the reduced surface field (RESURF) effect in the SOI layer.Both of them result in a high breakdown voltage (BV).Thirdly,the oxide trenches cause the drift region to be folded in the vertical direction,leading to a shortened cell pitch and a reduced R S,on.Fourthly,the trench gate extended to the BOX further reduces R S,on,owing to the electron accumulation layer.The BV of the MT MOSFET increases from 309 V for a conventional SOI lateral double diffused metal-oxide semiconductor (LDMOS) to 632 V at the same half cell pitch of 21.5 μm,and R S,on decreases from 419 m · cm 2 to 36.6 m · cm 2.The proposed structure can also help to dramatically reduce the cell pitch at the same breakdown voltage.     

拓扑绝缘体表面态的STM研究

文章主要介绍了利用扫描隧道显微镜对拓扑绝缘体表面态进行的一系列研究工作,包括拓扑绝缘体表面态的电子驻波以及拓扑表面态的朗道量子化现象.这些工作对于拓扑绝缘体基本性质的确立以及深入理解具有十分重要的意义.     

溶胶-凝胶固相微萃取涂层及其在农药残留分析中的应用

利用溶胶-凝胶(sol-gel)技术制备固相微萃取(SPME)涂层材料.通过硅醇盐前驱体与涂层聚合物羟基硅油(OH-TSO)的水解共聚的方法,成功地制备了聚二甲基硅氧烷sol-gel 涂层的SPME 萃取头,并以农药的混合标准水溶液为研究对象,用直接-固相微萃取-气相色谱法(GC)对涂层的性能进行考察,制成的萃取头适用于多种农药残留的萃取分离分析.     

MIL⁃53(Al)催化甲基氯硅烷的歧化机理

利用B3LYP/6?311++G(3df,2pd)方法计算了MIL?53(Al)的3个位点催化甲基氯硅烷以制备二甲基二氯硅烷的活性差异,并对反应通道、能量、过渡态虚振模式、内禀反应坐标(IRC)、关键原子间距的变化等进行了分析和讨论,得出了一致的结论:1~3号活性位催化的主反应速控步的活化能分别为157.15、155.31和123.44 kJ·mol-1;副反应速控步的活化能分别为206.48、214.87和166.07 kJ·mol-1。MIL?53(Al)能顺利催化歧化反应的原因在于其催化中心Al—O—H上的Br?nsted酸H,活性的差异来源于其配位环境的不同。     

体积排阻色谱-电感耦合等离子体质谱分析富硒大米含硒蛋白组成

建立体积排阻色谱-电感耦合等离子体质谱(SEC-HPLC-ICP-MS)联用技术分析富硒大米含硒蛋白组成方法。通过水提、盐提、碱提和醇提方法提取,并用丙酮沉淀蛋白,硒的回收率分别为9.6%,16.8%,48.2%和14.9%,纯化后的蛋白结合硒的量由大到小依次为碱溶谷蛋白>球蛋白>醇溶蛋白>清蛋白。蛋白液经SEC-HPLC-ICP-MS检测,通过蛋白色谱峰(λ=280 nm)和ICP-MS硒峰(78Se)对比分析,利用分子量标准曲线测定出4类蛋白中含硒蛋白的分子量。结果表明,富硒大米中清蛋白和醇溶蛋白并不是硒的主要存在蛋白。硒主要存在于>7 kDa的碱溶谷蛋白和球蛋白,其中碱溶含硒蛋白主要组分F1分子量为199.8 kDa。