巧用“不妨设”解题

当题目中的一些元素之间的关系具有多种可能性,并且不同的可能性并不影响题目结论和多功能解题方法时,我们便可通过“不妨设”选择其中一种可能性解题.请看一些例子.例1求代数式的值.三个数a、b、c的积为负数,和为正数,且x=|aa|+|bb|+|cc|+|aabb|+|aacc|+|bbcc|,求ax3+bx2+cx+1的值.分析:由已知可得a、b、c三数中有两个为正数,一个为负数,在x的表达式中a、b、c三数任意互换其中两个,原式不变,a、b、c具有同等地位,不失一般性,可不妨设a、b为正数,c为负数.解:由abc<0,a+b+c>0,得a、b、c中有两个正数,一个负数.在x的表达式中,不妨设a、b的正数…     

Simulation and experiments for the Q_ext of a cavity beam position monitor

The external Q (Qext) of the dipole mode is a key parameter of the Cavity Beam Position Monitor (CBPM). It determines the amplitude and length of the dipole mode signal. In this paper, Qext of a CBPM whose waveguides were open to the air was simulated and measured, and the results agreed with each other. Then four waveguide-to-coaxial cable adpaters were adjusted and assembled to the CBPM, and Qext remained unchanged. This progress provides a reliable method to evaluate Qext in the physics design without si...     

Design and experiments for the waveguide to coaxial cable adapter of a cavity beam position monitor

The waveguide to coaxial cable adapter is very important to the cavity beam position monitor (CBPM) because it determines how much of the energy in the cavity could be coupled outside. In this paper, the waveguide to coaxial cable adapter of a CBPM is designed and experiments are conducted. The curve shapes of experiments and simulations are very similar and the difference in reflection is less than 0.1. This progress provides a reliable method for designing the adapter.     

Simulation and experiments for the Qext of a cavity beam position monitor

The external Q （Qext） of the dipole mode is a key parameter of the Cavity Beam Position Monitor （CBPM）. It determines the amplitude and length of the dipole mode signal. In this paper, Qext of a CBPM whose waveguides were open to the air was simulated and measured, and the results agreed with each other. Then four waveguide-to-coaxial cable adpaters were adjusted and assembled to the CBPM, and Qext remained unchanged. This progress provides a reliable method to evaluate Qext in the physics design without simulating the structurally complex adapters.     

电感耦合等离子体原子发射光谱法测定铬矿中5种化学成分

提出了用电感耦合等离子体原子发射光谱法(ICP AES)测定铬矿中铁、铝、硅、镁和钙含量的方法。通过试验确定以混合熔剂碳酸钠-碳酸钾-硼砂质量比2比2比1熔融样品,熔块用硝酸(15+80)溶液浸取,分取部分试液按选定条件进行ICP-AES分析。选择393.37,251.61,271.44,396.15,279.55nm 5条谱线分别作为钙、硅、铁、铝及镁的分析线。用铬矿国家标准样品(BGBW 07201、GSBD 33001.3)制作标准曲线。按此方法对一种国家标准样品(GSBD 33001.2)和两种已知样品(Cr-2、72-Cr-01)进行分析。测定值与认定值基本一致,测得方法的回收率在99.0%～101.5%之间,相对标准偏差(n=6)在0.05%～0.78%之间。     

SOD1抑制与活性氧信号转导的调控

铜锌超氧化物歧化酶（Copper-zinc Superoxide Dismutase,SOD1）是胞内广泛存在的抗氧化酶,催化O₂^·-歧化为H₂O₂和O₂,维持胞内活性氧物种（ROS）内稳态。癌细胞的生长、增殖都依赖于适度高浓度的H₂O₂,高表达的SOD1维持癌细胞内较高水平的H₂O₂和ROS内稳态。抑制癌细胞内SOD1的活性,可以有效调节ROS信号通路,抑制癌细胞的生长、增殖,阻滞癌细胞周期,促进癌细胞凋亡。因此,通过抑制其活性调控癌细胞内ROS信号网络并选择性杀死癌细胞已经成为抗癌药物设计的一个重要方向。本文主要总结了各类SOD1抑制剂,以及SOD1抑制对ROS信号转导的调控,分析了SOD1特异抑制选择性杀死癌细胞的机制。     

杯[4]芳烃单取代1,3-二酮衍生物的合成及生物活性研究

以杯[4]芳烃为原料经醚化和克莱森缩合两步反应首次合成杯[4]芳烃单取代1,3-二酮衍生物,其结构经1H NMR、13C NMR及MS表征。初步的HIV-1整合酶链转移反应活性测试结果表明,该杯[4]芳烃单取代1,3-二酮衍生物在测试浓度为25μM时其抑制率为12.67%。     

双波长Yb∶YAG连续激光理论及实验研究

报道了Yb∶YAG双波长激光振荡阈值的理论结果,实验获得了连续双波长激光输出.实验中,采用紧凑的平凹腔结构、940nm光纤耦合LD端面泵浦方式,Yb∶YAG晶体作为激光晶体,采用10%、15%和20%的输出耦合镜,分别实现了单波长和双波长激光输出,在最高泵浦功率为20 W时,输出耦合率分别为10%、20%,最高获得3.94W的1 050nm激光和3.40 W的1 030nm激光,对应的光光转换效率分别为19.7%和17.0%;当输出耦合率为15%、泵浦功率为11.7 W时,获得0.79 W的双波长激光,对应的光光转换效率为6.8%,功率比为1∶1.3,通过光栅光谱仪测量得到双波长谱线中心分别为1 030.31nm和1 047.50nm;当1 030nm激光功率为3.0 W时,30min内输出功率RMS稳定性优于0.18%.该实验结果与理论分析相吻合,可应用于设计稳定可靠的掺Yb双波长激光器.