分散固相萃取-液相色谱-串联质谱法测定淡水鱼中柱孢藻毒素、节球藻毒素和微囊藻毒素

建立了同时检测淡水鱼中柱孢藻毒素、节球藻毒素、微囊藻毒素-RR、微囊藻毒素-YR及微囊藻毒素-LR的分散固相萃取-液相色谱-串联质谱方法。样品粉碎后，用乙腈-水-甲酸（89 ∶ 10 ∶ 1，v/v/v）提取目标物，C₁₈分散固相萃取柱净化，Agilent ZORBAX Eclipse XDB C₁₈色谱柱分离，乙腈和水梯度洗脱，在多反应监测（MRM）模式下进行定性分析，基质匹配标准曲线外标法定量。考察了提取溶剂及吸附剂种类对提取效率和净化效果的影响，并优化了液相色谱-串联质谱条件。该法在各自范围内具有良好线性关系，相关系数（R²）≥0.9954；检出限为5~10 μg/kg，定量限为15~40 μg/kg；样品的加标回收率为62.3%~101.2%。该方法前处理方法简单快速，灵敏高效，适用于淡水鱼中柱孢藻毒素、节球藻毒素和微囊藻毒素的有效检测。     

Effects of temperature change on the rheological property of modified multiwall carbon nanotubes

Applied Mathematics and Mechanics - Solvent-free nanofluids hold promise for many technologically significant applications. The liquid-like behavior, a typical rheological property of solvent-free...     

Bifurcation of traveling wave solutions of the $K(m, n)$ equation with generalized evolution term

In this paper, by using bifurcation theory and methods of plane dynamic system, we investigate the bifurcations of the traveling wave system corresponding to the $K(m, n)$ equation with generalized evolution term. Under different parameter conditions, some exact explicit parametric representations of traveling wave solution are obtained.     

微流控芯片电泳-多重聚合酶链反应法同时测定多个单碱基多态性位点

以微流控芯片电泳为检测平台,建立了多重PCR扩增法同时测定多个单碱基多态性(SNP)位点的方法。先通过PCR扩增得一段含所有待测SNP位点的长片段;用限制性内切酶消化成短片段,再将酶切反应产物与脱氧核糖核酸适配器(DNAadapter)相连;以连接产物为模板,分成两管,分别用n条等位基因特异性引物和一条通用引物进行n重PCR扩增;最后用微流控芯片电泳法分离PCR扩增产物,根据两管扩增产物的芯片电泳图谱中扩增片段的大小判断SNP的类型。以细胞色素P4502D6(CYP2D6)基因中的5个SNP位点(100C>T、1661G>C、1758G>T、2470T>C和2850C>T)为检测对象,考察了各等位基因特异性引物之间的相互影响和扩增反应的特异性,采用微流控芯片电泳法成功测定了20名健康中国人的CYP2D6基因中5个SNP位点的基因多态性,与聚合酶链反应-限制性片段长度多态性法(PCR-RFLP)测定结果完全一致。     

Codimension 3 Nontwisted Double Homoclinic Loops Bifurcations with Resonant Eigenvalues

This paper presents the nontwisted double-homoclinic-loop bifurcations with resonant eigenvalues in four dimensional vector fields. The Poincaré map is established to solve various problems in double-homoclinic-loop bifurcations with codimension 3. Bifurcation diagrams and bifurcation curves are given. Dedicated to Professor Zhifen Zhang on the occasion of her 80th birthday     

Cobalt‐Catalyzed C(sp2)−H Methylation by using Dicumyl Peroxide as both the Methylating Reagent and Hydrogen Acceptor

The first cobalt‐catalyzed direct methylation of a C(sp²)?H bond using dicumyl peroxide (DCP) as both the methylating reagent and hydrogen acceptor has been established. The reaction proceeded without the use of any additives, and was proven to be applicable to various amides bearing a 2‐pyridinylisopropyl (PIP) directing group, providing an efficient access to o‐methyl aryl amides with high functional‐group tolerance. Preliminary mechanistic studies suggest a radical process would be involved in the catalytic process.     

Nonlinear characterization of the rotor-bearing system with the oil-film and unbalance forces considering the effect of the oil-film temperature

Nonlinear Dynamics - The nonlinear phenomena of the rotor-bearing systems, i.e., the oil whirl, oil whip, quenching and pulling out, due to the oil-film temperature are not yet clear. To...     

吲哚酚显色底物的合成及其在微生物检测中的应用研究进展

吲哚酚显色底物是由作为产色原的吲哚酚或其取代物与酶底物间接缩合而成,其合成主要包括中间体乙酸1-乙酰基-吲哚-3-基酯的合成及其与酶底物的衍生物缩合两部分。中间体可以通过以取代苯胺、邻氨基苯甲酸、邻氯苯甲酸等为起始物合成,而其再与酶底物的衍生物如乙酰溴代糖、酰卤、三氯氧磷、氯磺酸等反应可得到相应的各种显色底物。吲哚酚显色底物应用于微生物检测,依据特异性酶与相应底物的特异性反应,一般通过显色培养基技术来实现,不同的显色底物针对的酶及其应用于检测的微生物会有所不同。     

Circular whirling and stability due to unbalanced magnetic pull and eccentric force

This rapid communication is concerned with the circular whirling and stability of a model rotor in a synchronous generator under no load, subjected to unbalanced magnetic pull and mass eccentric force. The analysis is focused on the synchronous whirling of the rotor. Based on the existing analytical expression for unbalanced magnetic pull with any pole-pair number, the nonautonomous system of differential equations of motion with parametrically exciting force is transformed to an autonomous one by introducing a rotating coordinate frame. The circular whirlings of the model rotor are thus converted into equilibrium solutions to the autonomous system, which can be obtained by solving a system of polynomial equations with two unknowns only. Furthermore, stability of these equilibrium solutions is determined by applying the linearized stability criterion. An example is used to illustrate the proposed analytical method.