LC-DAD-APCI-MS-based screening and analysis of the absorption and metabolite components in plasma from a rabbit administered an oral solution of danggui

A valid chromatographic fingerprint method using liquid chromatography-diode array detection-atmospheric pressure chemical ionization mass spectrometry in negative mode (LC-DAD-APCI-MS) is proposed for studying the absorption and metabolites of a traditional Chinese medicine (TCM) Angelica sinensis (danggui) in rabbit plasma, after the rabbit is administered with danggui oral solution (DOS). More than thirty-two common components were detected in both DOS and rabbit plasma, which shows that the components in the DOS were absorbed into the body of the rabbit. Of these, senkyunolide I, senkyunolide H, Z-6,7-epoxyligustilide, 3-butylidene-7-hydroxyphthalide, Z-ligustilide, Z-butylidenephthalide, Diels-Alder dimers of ligustilide, linolenic acid, linoleic acid and falcarindiol were tentatively identified from their MS, UV spectra and retention behavior by comparing the results with the published literature. At least ten components were found in rabbit plasma but not in DOS, indicating that these components must be metabolites of some of the components in the original extract. The results prove that the proposed method can be used to rapidly analyze multiple constituents in TCMs, and to screen for bioactive compounds by comparing and contrasting the chromatographic fingerprints of DOS and plasma samples.     

Preparation of a novel fluorescence probe based on covalent immobilization by emulsion polymerization and its application to the determination of metronidazole

A novel method of preparing fluorescence particle probe by emulsion polymerization with covalent immobilization of indicator dye was described. A terminal double bond was attached to 3-amino-9-ethylcarbazole (AEC) via methacryloyl chloride, and the resultant compound was copolymerized with butyl methacrylate. The obtained polymer particles were used as a fluorescence probe, which is almost free of dye leaching, and has higher photostability and lower toxicity in comparison with free AEC. This probe holds great potential for the applications in intracellular measurements. In present study the prepared probe was used for the determination of metronidazole. The results revealed that the probe showed good selectivity and had a linear response to the analyte in the range from 2.0 × 10⁻⁵ to 1.0 × 10⁻³ mol l⁻¹ with a detection limit of 9.0 × 10⁻⁶ mol l⁻¹.     

Positive periodic solutions of impulsive functional differential equations

We study the existence and nonexistence of positive periodic solutions of a non-autonomous functional differential equation with impulses. The equations we study may be of delay, advance or mixed type functional differential equations and the impulses may cause the existence of positive periodic solutions. The methods employed are fixed-point index theorem, Leray-Schauder degree, and upper and lower solutions. The results obtained are new, and some examples are given to illustrate our main results.     

Periodic solutions of higher-order delay differential equations

In this paper, we prove existence results for periodic solutions concerning the higher-order delay differential equations. Our method is based upon the coincidence degree theory of Mawhin. The results obtained are new. Examples are given to illustrate the main results.     

基于信号稀疏分解的水下回波分类

针对表面起伏不平的水下底质回波分类效果差的问题,提出一种新颖的基于信号稀疏分解理论的水下底质回波特征提取方法。本方法并不使用通用时频字典,而是针对回波分类这一中心任务直接采用回波训练样本集作为字典,将水下回波信号在该字典上进行稀疏分解,然后提取出回波信号的类别能量特征。对水下钴结壳等三类底质回波分类实验表明,基于信号稀疏分解的类别能量特征的fisher分布明显优于小波域模极大值边缘特征和奇异值特征,从而显著提高了水下回波的分类效果。研究结论:在回波特征提取阶段,采用回波样本作为信号表达字典是可行的,同时由回波样本字典引入的回波类别信息将有助于获取更优的回波特征。      

Analysis of permeability for the fractal-like tree network by parallel and series models

This work investigates the hydraulic conductivity properties in the fractal-like tree networks between one point and a straight line. The expression for the effective permeability of the networks is derived based on the parallel and series models and the relationship between the effective permeability and the geometry structures of the network is analyzed. It is found the effective permeability after including tortuosity is about 20% lower than that without considering the tortuosity, and the tortuosity effect should be included in analysis of hydraulic conductivity properties in the networks; the effective permeability is very sensitive to the geometrical structures of the network. A comparison of the fractal-like tree network with the traditional parallel net indicates that the fractal-like tree network can provide much higher permeability than that of the traditional parallel net.     

A simple approach to solving double sinh--Gordon equation

By introducing an auxiliary ordinary differential equation and solving it by the method of variable separation abundant types of explicit and exact solutions for the double sinh-Gordon equation are derived in a simple manner.     

正确选择独立回路的两种方法

分析了两种选择独立回路的错误作法,给出了两种正确选择独立回路的方法,即单链回路法和平面网孔法．     

结石患者和健康对照者尿微晶生长、聚集过程的比较研究

采用扫描电子显微镜(SEM)和X-射线粉末衍射仪(XRD)比较研究了5例泌尿系结石患者和5名健康对照者的尿微晶的生长动力学差异。随着生长时间(t)增加,结石患者尿微晶尺寸不断增大,粒径从t=1 h时的约(6±4)μm增加到t=48 h的(29±17)μm,但微晶数密度从(1 400±300)mm-2逐渐减少至(450±140)mm-2,表明在患者尿液中微晶的形成过程为生长控制;相比之下,在对照者尿液中,随着t从1 h增加48 h,尿微晶数密度从(850±260)mm-2减少至(610±210)mm-2,微晶尺寸从(6±5)μm增加至(15±9)μm,这表明其生长过程同时为成核控制和生长控制。上述差异归因于对照者尿液中抑制剂的浓度和活性均比结石患者的高,更能抑制尿微晶的生长和聚集。