气相色谱-质谱法快速筛选测定浓缩苹果汁中105种农药残留量

采用硅藻土柱层析法对样品中的农药进行提取及净化后，用气相色谱—质谱法在选择离子监测模式下进行快速测定，以保留时间和特征离子定性定量；采用此方法测定了包括有机氯农药、有机磷农药、氨基甲酸酯农药、拟除虫菊酯农药、三嗪类农药在内的105种农药，大多数农药的线性范围为0.05～10mg／kg，相关系数大于0.99；90％以上农药在0．2mg／kg添加水平的平均回收率在70％～110％的范围内。     

50 GHz optical true time delay beamforming in hybrid optical/mm-wave access networks with multi-core optical fiber distribution

We propose and experimentally validate an optical true time delay beamforming scheme with straightforward integration into hybrid optical/millimeter(mm)-wave access networks. In the proposed approach, the most complex functions, including the beamforming network, are implemented in a central office, reducing the complexity and cost of remote antenna units. Different cores in a multi-core fiber are used to distribute the modulated signals to high-speed photodetectors acting as heterodyne mixers. The mm-wave carrier frequency is fixed to 50 GHz(VBand), thereby imposing a progressive delay between antenna elements of a few picoseconds. That true time delay is achieved with an accuracy lower than 1 ps and low phase noise.     

Numerical tests of theoretical models describing ionization of H(1s) atom by linearly polarized flat pulse of laser radiation

We derive the well-known Coulomb correction factor for the Gordon-Volkov wave function describing an outgoing electron in the process of ionization in an intense laser field. Although rigorous treatment would limit its use only to laser fields much lower than the so-called barrier-suppression field, it appears that in practice the correction factor may be used also close to and even above this critical value of the laser field. We compare predictions of several analytical expressions describing ionization rate of the hydrogen atom in its ground state in the strong linearly polarized laser field. We also compare ionization probabilities obtained by integrating these ionization rates over a temporal envelope of the laser pulse with predictions based on the exact numerical solution to the time-dependent Schr ¨odinger equation.     

On a certain classes of meromorphic functions with positive coefficients

In this paper certain classes of meromorphic functions in punctured unit disk are defined. Some properties including coefficient inequalities, convolution and other results are investigated.     

On the Differential Polynomial of a Graph

We introduce the differential polynomial of a graph. The differential polynomial of a graph G of order n is the polynomial B(G; x) :=∑?(G)k=-nB_k(G) x~(n+k), where B_k(G) denotes the number of vertex subsets of G with differential equal to k. We state some properties of B(G;x) and its coefficients.In particular, we compute the differential polynomial for complete, empty, path, cycle, wheel and double star graphs. We also establish some relationships between B(G; x) and the differential polynomials of graphs which result by removing, adding, and subdividing an edge from G.     

一个奇摄动微分方程非线性混合边值问题

研究了一个三阶半线性微分方程的奇摄动非线性混合边值问题.利用边界层函数法构造了该问题的形式渐近解,并采用微分不等式理论证明了解的存在性,给出了渐近解的误差估计,最后得出了边界层函数指数型衰减的结论.     

质谱分子成像技术与应用进展

该文总结了二次离子质谱、基质辅助激光解吸电离质谱和常压敞开式离子化质谱三大类型质谱分子成像（MSI）技术的概况、技术与方法及其应用新进展。MSI技术作为免标记、高覆盖、高灵敏、检测范围广的可视化分析手段,不局限于生物组织或细胞中某种特定分子的检测,可对已知和未知多种分子进行同时成像分析,获得不同分子的空间分布、相对含量及结构信息,实现其分子的定性、定量与定位分析;还可提供不同生理及病理过程中功能分子的动态时空变化信息等。因此,MSI技术成为质谱领域以及分析化学等领域的研究前沿与热点方向之一,并在化学、医学、生命科学、药学和环境科学等领域显示出重大应用前景。此外,MSI技术是单细胞可视化分析和空间分辨代谢组学的强有力分析手段,可从动物或器官组织的整体、微区、单细胞等不同空间尺度,获取具有空间分布特征、时空动态变化的功能分子全景轮廓信息等而备受关注。     

A PREDATOR-PREY SYSTEM WITH STAGE STRUCTURE AND HARVESTING FOR PREDATOR

In this paper, we consider a predator-prey system with stage structure and harvesting (where the predator population has two stages, an immature stage and a mature stage with harvesting, and the growth of the prey population is of Lotka-Volterra nature). We obtain the conditions of the globally asymptotic stability for three nonne-gative equilibria of this system.