The interstellar methanol masers and their environments

To promote the understanding of massive star formation processes, we have studied the 6.6 GHz methanol (CH3OH) masers and their environments-- the dense cores and the outer regions of the molecular cloud. The physics of the CH3OH maser or the thermal emission formation region is studied by fitting the observational data of the 6.6 GHz 51-60 A+ and the 107 GHz 31-40 A+ CH3OH maser emission, using the radiative transfer calculations. The type II characteristics of the 6.6 GHz CH3OH maser are confirmed by the calculation results. A greater intensity of the radiation field leads to an increase in the peak intensity of the maser; however, high densities tend to turn off the maser. The calculation results show that to be a maser the 6.6 GHz CH3OH emission needs a radiation field of 150-300 K and a density not higher than 107cm-3, while the 107 GHz emission requires a radiation field of 210-300 K and a density not higher than 3×106 cm-3. The 6.6 GHz line is maser towards all six studied sources, while the 107 GHz line is maser towards Cep A only. Moreover, the former's intensity is much stronger than the latter. The radiative transfer calculations also indicate that the 6.6 GHz maser emission is so strong that the requirements of its formation (e.g. The radiation field, the density and the kinetic parameters) can only be satisfied at a certain stage of the processes of the massive star formation. Therefore it is often used as one of the most prominent tracers for the massive star formation regions. The calculation results of the simultaneous observations of (1,1) through (4,4) inversion lines of the ammonia (NH3) indicate that both the temperature and the density in the 6.6 GHz CH3OH maser formation regions are higher than that of the NH3 line formation regions. Furthermore, the common fact of |Vlsr(CO)| ＞ |Vlsr(NH3)| ＞ |Vlsr(CH3OH 6.6GHz maser)| in all six sources implies the ongoing developing trends of those gas flows driven by the masers.     

基于一维锌(Ⅱ)配位聚合物的水中2,4,6-三硝基苯酚和氟啶胺的选择性检测（英文）

以1,1’∶4’,1’’∶4’’,1’’’-四联苯-2,4,2’’’,4’’’-四羧酸(H₄L)和4,4’-联吡啶(4,4’-bpy)为配体,采用水热法合成了一维锌配位聚合物[Zn₂(H₂L)₂(4,4’-bpy)₂(H₂O)]_n(1),并通过单晶X射线衍射分析、元素分析、红外光谱分析和热重分析等方法对其结构进行了表征。单晶结构分析表明1属于三斜晶系,空间群为■。配合物1含有2种配位构型不同的锌离子,分别处于扭曲的三角双锥{ZnNO₄}和八面体{ZnNO₅}几何构型中。配合物中2个H₂L^2-配体之间通过锌离子相互连接,构成了无限的一维zigzag平面结构。荧光传感实验表明配合物1的荧光能够被2,4,6-三硝基苯酚和氟啶胺猝灭,且具有较高的灵敏度和选择性,抗干扰性也非常好。     

复值函数的广义复模糊积分北大核心

本文给出了非负复值函数关于模糊复测度的广义复模糊积分的几种等价形式,并讨论了由该积分表示的几种复模糊积分方程有解的充要条件.在此基础上,进一步引进了一般复值函数的广义复模糊积分的概念,给出了该积分的一些基本性质,并在一定条件下证明了单调收敛定理.     

蛇莓果实总花色苷含量测定方法的比较

为了寻求快速、经济地测定蛇莓果实总花色苷含量的方法,采用单-pH法和pH示差法进行测定,比较分析了两种方法测定结果的差异性.结果表明,两种pH法测定的吸光度与浓度均具有良好的线性关系,测定结果没有显著性差异.两种pH法均能用于蛇莓果实总花色苷含量的测定,且需要在相同溶剂中进行,其中单一pH法操作更简便.     

微流控芯片上大肠杆菌的电化学阻抗检测方法研究

基于细菌悬浮液的阻抗特性和微流控芯片电化学阻抗检测技术,采用所构建的微流控芯片电化学阻抗分析系统,以大肠杆菌为样本,优化了扰动振幅、缓冲溶液电导率、扫描频率和新制大肠杆菌标本静置时间等参数,对大肠杆菌标本、大肠杆菌标准合成样本进行电化学阻抗检测,建立了一种大肠杆菌快速定量检测方法.在扰动振幅500 mV、缓冲溶液电导率...     

Observation of the BEC-BCS crossover in a degenerate Fermi gas of lithium atoms

We observe characteristic atomic behaviors in the Bose-Einstein-condensation-Bardeen-Cooper-Schrieffer(BEC-BCS)crossover,by accurately tuning the magnetic field across the Feshbach resonance of lithium atoms.The magnetic field is calibrated by measuring the Zeeman shift of the optical transition.A non-monotonic anisotropic expansion is observed across the Feshbach resonance.The density distribution is explored in different interacting regimes,where a condensate of diatomic molecules forms in the BEC limit with the indication of a bimodal distribution.We also measure the three-body recombination atom loss in the BEC-BCS crossover,and find that the magnetic field of the maximum atom loss is in the BEC limit and gets closer to the Feshbach resonance when decreasing the atom temperature,which agrees with previous experiments and theoretical prediction.This work builds up a controllable platform for the study on the strongly interacting Fermi gas.     

阻抗匹配条件下磁控管的注入锁频

单只磁控管输出功率不能满足大规模工业应用, 需要对多只磁控管进行相干功率合成. 为解决普通磁控管相干功率合成所需的相位一致性, 需要对普通磁控管引入注入锁频技术, 以保障工作频率和相位差的稳定性. 本文在阻抗匹配的条件下, 结合磁控管稳定振荡的条件, 从等效电路的角度出发对磁控管注入锁频原理进行分析, 给出了在小注入比和大注入比情况下磁控管的注入锁频理论, 大注入比情况比小注入比情况给出了更大的锁频带宽. 采用MATLAB对理论方程进行解析求解, 同时通过三维粒子仿真软件对锁频理论进行了对比验证, 得出了在不同注入比下磁控管的锁频带宽和相位差微分方程, 给出了在不同初始相位下的相位差变化曲线, 得到了A6磁控管在自由振荡和注入锁频工作下三维模拟仿真的输出功率、频率和波形. 模拟结果表明, 在两种情形预测的锁频带宽内, 磁控管均能被锁定并稳定工作, 在大注入比下大注入比情况比小注入比情况更为准确. 关键词： 磁控管 注入锁频 注入比 相位差     

光电联合催化的研究进展

近年来,温和、绿色的光化学和电化学反应在有机合成中得到了广泛的应用.为了进一步提升光、电反应潜力,有机化学家们致力于在单一反应体系中使用这两种策略来促进有机转化.一系列光电联合催化策略被开发出来,目前主要的光电联合催化策略是电化学介导的光氧化还原催化.此外,光激发辅助、电化学主导氧化还原的光电联合催化策略也逐渐展现出其...     

为什么简单的想法学生不接受——基于数学理解的教学案例研究

1问题提出2010年10月,我校数学教研组开展教研活动,一位教龄近十年的中年教师开设了公开课,内容是高一年级的"函数的单调性"新授课.教师在教完"增函数"的概念后,为了检测学生对"增函