加速器质谱法研究尼古丁与小鼠血液蛋白的加合作用

采用加速器质谱法（AMS）研究了小鼠血液中的血红蛋白（Hb),白蛋白（SA）和尼古丁和加合作用，在尼古丁剂量从相应于人吸烟的环境剂量水平0．1μg/kg体重到100μg/kg体重范围内，测量了尼古丁－血红蛋白加合物和尼古丁－白蛋白加合物的剂量效应曲线，两种蛋白的尼古丁加合物水平都随着尼古丁剂量的升高耐线性增加，在实验剂量范围内，两种蛋白质加合物的水平与小鼠肝DNA加合物水平也呈现良好的线性关系，这说两种蛋白质加合可以替代DNA加合物作为尼古丁的生物标记物，在本工作中，蛋白质加合物的测量灵敏度为0．03pmol/g蛋白（即3．2个加合物／10^12氨基酸残基），达到了文献报道的测量蛋白质生物标记物最高的灵敏度。     

双极性脉冲磁控溅射电源设计

双极性脉冲电源是磁控溅射系统中的关键设备之一。根据铌溅射处理装置的技术要求,研制了一套输出电压0~800 V可调、脉冲宽度20~200 μs可调、频率0~60 Hz可调、脉冲电流最大幅值约150 A的双极性脉冲电源,分别给出了该电源在水电阻负载和等离子体负载下的实验结果。设计上采用DSP控制开关电源的方式对储能电容器进行恒流充电;综合应用FPGA,PLC及触摸屏组成人机交互系统,控制输出光脉冲信号,经负压偏置驱动后使桥式结构的脉冲形成网络产生正负交替双极性脉冲。通过大量实验论证,该电源解决了等离子体负载放电打弧等问题,达到了理想的溅射效果,满足了指标要求。     

CLBO晶体生长与紫外倍频性能研究

CLBO晶体是一种性能优良的新型激光紫外倍频晶体材料,本文采用改进的顶部籽晶法生长出大尺寸、高光学质量的CLBO晶体.用尺寸为6mm×5mm×10mm的CLBO四倍频样品测量了晶体对Nd:YAG,1064nm四倍频的紫外倍频性能,266nm激光输出功率达到780mW.针对CLBO晶体的潮解开裂问题,在CLBO倍频器工作和存放时,采用恒温加热套管保护,有效地防止了晶体的潮解开裂.     

北京大学加速器质谱计

北京大学重离子物理研究所和技术物理系研制的加速器质谱计于１９９２年圆满建成并投入使用．在两年多的运行中,性能不断得到改进,并取得了大量的应用成果．简要介绍其性能特点、运行情况和应用概况.The accelerator mass spectrometry studied by the Institute of Heavy Ion Physics and the Department of Technical Physics,Peking University,was successfully manufactured in 1992.In the two years routine operation,the machine performances have been improved and some application achievements have been obtained.In this paper feature of the machine,opeartion and some applications are given.     

CAEP太赫兹自由电子激光首次饱和出光

中国工程物理研究院基于超导射频直线加速器的谐振腔型太赫兹自由电子激光(CTFEL)于2017年8月29日16时首次饱和出光,并稳定运行,中心频率2.56 THz,谱宽1.9%,宏脉冲平均功率大于5.7 W。     

A preliminary quadrupole asymmetry study of a Iβ=0.12 superconducting single spoke cavity

An Accelerator Driven System (ADS) has been launched in China for nuclear waste transmutation. For the application of high intensity proton beam acceleration, the quadrupole asymmetry effect needs to be carefully evaluated for cavities. Single spoke cavities are the main accelerating structures in the low energy front-end. The single spoke cavity has small transverse electromagnetic field asymmetry, which may lead to transverse RF defocusing asymmetry and beam envelope asymmetry. A superconducting single spoke resonator (PKU-2 Spoke) of β =0.12 and f=325 MHz with a racetrack-shaped inner conductor has been designed at Peking university. The study of its RF field quadrupole asymmetry and its effect on transverse momentum change has been performed. The quadrupole asymmetry study has also been performed on a β =0.12 and f=325 MHz ring-shaped single spoke cavity. Our results show that the quadrupole asymmetry is very small for both the racetrack-shaped and the ring-shaped single spoke cavity.     

初中化学基础实验:解读中重构——以“家用清洁剂探究”一课为例

初中化学基础实验需要教师理解课标修订,智慧解读教材,重视功能挖掘。对于酸、碱的化学性质基础实验,尝试开发家用清洁剂这一生活资源,让学生在全新的情境中重温酸、碱的化学性质,不仅提高实验技能,更发展实验智能。     

Electromagnetic design and optimization of a superconducting quarter wave resonator

Superconducting (SC) cavities currently used for the acceleration of protons at a low velocity range are based on half wave resonators. Due to the rising demand on high current, the issue of beam loading and space charge problems has arisen. Qualities of low cost and high accelerating efficiency are required for SC cavities, which are properly fitted by using an SC quarter wave resonator (QWR). We propose a concept of using QWRs with frequency 162.5 MHz to accelerate high current proton beams. The electromagnetic design and optimization of the prototype have been finished at Peking University. An analytical model derived by the transmission line theory is used to predict an optimal combination of the geometrical parameters, with which the calculation by Microwave Studio shows a good agreement. The thermal analysis to identify the temperature rise of the demountable bottom plate under various levels of thermal contact also has been done, and the maximum increment is less than 0.5 K even though the contact state is poor.     

用于DC–SC超导光电子枪中的光阴极的研制

DC-SC超导光阴极微波电子枪是一种新型的高平均流强电子源,本文介绍了其中的关键部件—光阴极的研制.在自行研制的光阴极制备室里成功制备了两种光阴极:Cs₂Te和Cs₃Sb光阴极.Cs₂Te光阴极的寿命长,用266nm紫外光激发,量子效率QE>25%,真空中(1×10^－5Pa)寿命50h.Cs₃Sb光阴极是多层膜结构,用532nm激光激发,量子效率2%,真空中(10^－5Pa)寿命只有几个小时.两者都可以满足电子枪的设计要求,但是由于Cs₂Te光阴极更稳定,在目前的DC-SC超导光电子枪调试实验中采用这种光阴极     

光学活性N-肉桂酰R(S)-4-异丙基四氢噻唑-2-硫酮的合成及其 量子化学的研究

用KBH~4,CaCl~2为还原使D及L缬氨酸甲酯还原得到光学活性产物R-3-甲基-2-氨基丁醇(2a)及S-3-甲基-2-氨基丁醇(2b)。2a,2b同CS~2在KOH存在下反应得到(R)-4-异丙基四氢噻唑-2-硫酮(3a)及(S)-4-异丙基四氢噻唑-2-硫酮(3b)。肉桂酰氯分别同3a及3b在Et~3N存在下反应得到N-肉桂酰(R)-4-异丙基四氢噻唑-2-硫酮(4a)及N-肉桂酰(S)-4-异丙基四氢噻唑-2-硫酮(4b)。用半经验的量子化学PM3方法研究了反应物和产物的电子结构,得到了产物的最优构型和电荷键序分布以及反应焓变。