四极杆-线形离子阱液相色谱质谱联用法快速检测玉米油中黄曲霉毒素

建立了四极杆-线形离子阱液相色谱质谱联用仪(Liquid Chromatography-Quadrupole-Linear Ion Trap Mass Spectrometry,LC-Q-LIT)测定玉米油中4种黄曲霉毒素(黄曲霉毒素B_(1)、黄曲霉毒素B_(2)、黄曲霉毒素G_(1)、黄曲霉毒素G_(2))的分析方法。选择Phenomenex Kinetex C_(18)色谱柱(2.1 mm×50 mm,2.6μm)分离目标物,分别以0.1%甲酸水-0.1%甲酸甲醇(V/V)为流动相进行梯度洗脱。质谱采用正离子扫描(ESI+)和选择反应监测模式。在玉米油基质中,4种黄曲霉毒素在2.5~50.0 ng·mL^(-1)呈现良好的线性关系(R^(2)≥0.990 3),检测限和定量限在0.5~1.0 ng·mL^(-1)和1.5~2.5 ng·mL^(-1),添加回收率为71.75%~97.87%,RSD≤13.86%。该方法操作简单、快速、成本低且灵敏度高,定性、定量准确,适用于玉米油中黄曲霉毒素的检测分析。

2.5D boundary element simulation of wave propagation in a vertical fluid-filled borehole with irregular shape

In this paper, a boundary element formulation in the wave-number space domain for solving the wave equation for a borehole with arbitrary shape in acoustic logging problems is presented. The problem is treated as a two-dimensional medium with the discrete wave- number method in the vertical direction. The method is validated by comparing the results obtained by this method with those obtained by the finite-difference method. The method is used to study the effect on wave propagation in a vertical borehole of a vertical fracture. For a monopole source, the dispersion curves for Stoneley waves yield three branches. For dipole and quadrupole sources, different orientations of the source yield different results. When the dipole source is orthogonal to the fracture, the dispersion curve is similar to that of the open hole, while the curves are quite different when the source is parallel to the fracture. These characteristics enable us to determine the orientation of the vertical fracture.

COLORED NOISE PREDICTION BASED ON NEURAL NETWORK

A method for predicting colored noise by introducing prediction of nonlinear time series is presented. By adopting three kinds of neural networks prediction models, the colored noise prediction is studied through changing the filter bandwidth for stochastic noise and the sampling rate for colored noise. The results show that colored noise can be predicted. The prediction error decreases with the increasing of the sampling rate or the narrowing of the filter bandwidth. If the parameters are selected properly, the prediction precision can meet the requirement of engineering implementation. The results offer a new reference way for increasing the ability for detecting weak signal in signal processing system.

Pulse Amplification in Dispersion-Decreasing Fibers with Symbolic Computation

The pulse amplification in the dispersion-decreasing fiber （DDF） is investigated via symbolic computation to solve the variable-coefficient higher-order nonlinear Schrfdinger equation with the effects of third-order dispersion, self-steepening, and stimulated Raman scattering. The analytic one-soliton solution of this model is obtained with a set of parametric conditions. Based on this solution, the fundamental soliton is shown to be amplified in the DDF. The comparison of the amplitude of pulses for different dispersion profiles of the DDF is also performed through the graphical analysis. The results of this paper would be of certain value to the study of signal amplification and pulse compression.

现代主义美术在1950至1970年代的调适——杨秋人的油画艺术及时代意义

文章以杨秋人的油画风景为主要研究对象,梳理了其油画作品存世及相关研究的学术史,对其早期作品和新中国时期作品进行比照的基础上分析其油画的形式特征和风格成因。认为杨秋人尝试将中国传统山水画的意蕴和西方现代主义美术形式相结合,进而与现实主义美术调适,探索油画的民族风格和中国气派。

Impact of otrA expression on morphological differentiation,actinorhodin production,and resistance to aminoglycosides in Streptomyces coelicolor M145

otrA resembles elongation factor G （EF-G） and is considered to be an oxytetracycline （OTC）-resistance determinant in Streptomyces rimosus. In order to determine whether otrA also conferred resistance to OTC and other aminoglycosides to Streptomyces coelicolor, the otrA gene from S. rimosus M527 was cloned under the control of the strong ermE promoter. The resulting plasmid, pIB139-otrA, was introduced into S. coeficolor M145 by intergenedc conjugation, yielding the recombinant strain S. coelicolor M145-OA. As expected S. coelicolor M145-OA exhibited higher resistance levels specifically to OTC and aminoglycosides gentamycin, hygromycin, streptomycin, and spectinomycin. However, unexpectedly, S. coelicolor M14-~OA on solid medium showed an accelerated aerial mycelia formation, a precocious sporulation, and an enhanced actinorhodin （Act） production. Upon growth in 5-L fermentor, the amount of intra- and extracellular Act production was 6-fold and 2-fold higher, respectively, than that of the original strain. Consistently, reverse transcription polymerase chain reaction （RT-PCR） analysis revealed that the transcrip- tional level of pathway-specific regulatory gene acUl-orf4 was significantly enhanced in S. coelicolor M145-OA compared with in S. coelicolor M145.