Picolinyl ester fragmentation mechanism studies with application to the identification of acylcarnitine acyl groups following transesterification

Acyl picolinyl esters provide excellent data to identify the structures of acyl groups. However, the mechanisms for the formation of fragment ions from picolinyl esters are unsettled. Proposed structures for fragment ions have focused on long-chain groups and may not accommodate results from medium- and short-chain acyl groups. Using deuterium-labeled organic acids, we have investigated the mechanisms for the formation of fragment ions. Based on these studies, we propose a new mechanism that is consistent with the experimental data. We then tested the mechanisms by analyzing selected acylcarnitines. Transesterification of acylcarnitines was performed by reaction with 3-pyridylcarbinol and potassium tert-butoxide in dichloromethane to produce acyl picolinyl esters. The picolinyl esters were separated and detected by gas chromatography/electron ionization-mass spectrometry. Each mass spectrum contained a series of peaks with m/z differences of 12, 13, or 14 u depending on the acyl group's chemical structure. The position of an unsaturated bond or branched methyl in the acyl group of acylcarnitine can be readily determined.     

Simple fluorimetric liquid chromatographic method for the analysis of undecylenic acid and zinc undecylenate in pharmaceutical preparations

A simple and selective liquid chromatographic method is described for the analysis of undecylenic acid (UA) and zinc undecylenate (ZnUA) in pharmaceutical preparations. The method is based on the derivatization of the analytes extracted from various samples with 2-(2-naphthoxy)ethyl 2-(piperidino)ethanesulfonate. The resulting derivative was analyzed by liquid chromatography with fluorimetric detection. The quantitation of the method is in the range of 3.0-50.0 microM UA with a detection limit of about 0.3 microM (S/N = 3 with 10 microl injection). We found that acetonitrile is a selective solvent for differentially dissolving UA from coexisted ZnUA in compound formulation. This results in the specific analysis of UA in the presence of ZnUA and simply analyzing the coexisted ZnUA by the value of total UA (UA+ZnUA) minus that of UA. Application of the method to the analysis of undecylenic acid and zinc undecylenate in ointment, powder and solution preparations proved feasible.     

Rank-one cross commutators on backward shift invariant subspaces on the bidisk

For a backward shift invariant subspace N in H^2（Г^2）, the operators Sz and Sw on N are defined by Sz = PNTz｜N and Sw, = PNTw｜N, where PN is the orthogonal projection from L^2（Г^2） onto N. We give a characterization of N satisfying rank [Sz, Sw^＊] = 1.     

Quasilinear elliptic equations with Neumann boundary and singularity

Let Ω be a bounded domain with a smooth C2 boundary in RN（N ≥ 3）, 0 ∈Ω, and n denote the unit outward normal to ЭΩ.We are concerned with the Neumann boundary problems： -div（｜x｜α｜△u｜p-2△u）=｜x｜βup（α,β）-1-λ｜x｜γup-1,u（x）〉0,x∈Ω,Эu/Эn=0 on ЭΩ,where 1〈p〈N and α〈0,β〈0 such that p（α,β）△=p（N＋β）/N-p＋α〉p,y〉α-p.For various parameters α,βorγ,we establish certain existence results of the solutions in the case 0∈Ω or 0∈ЭΩ.     

Semilocal convergence of a modified multi-point Jarratt method in Banach spaces under general continuity condition

The semilocal convergence for a modified multi-point Jarratt method for solving non-linear equations in Banach spaces is established with the third-order Fréchet derivative of the operator under a general continuity condition. The recurrence relations are derived for the method, and from this, we prove an existence-uniqueness theorem, and give a priori error bounds. The R-order of the method is also analyzed with the third-order Fréchet derivative of the operator under different continuity conditions. Numerical application on non-linear integral equation of the mixed type is given to show our approach.     

Determination of nitrofurans in feeds based on silver nanoparticle-catalyzed chemiluminescence

A highly sensitive chemiluminescence (CL) method for the determination of nitrofurans (NFs) was developed based on the enhancement of CL intensity of luminol–H₂O₂–NFs system by silver nanoparticles (AgNPs). It was supposed that the oxygen-related radicals of OH and superoxide radical (O₂^?) could be produced when NFs reacted with H₂O₂. Furthermore, the enhancement mechanism was originated from the reinforcer of AgNPs, which could catalyze the generation of the OH radical. Then OH radicals reacted with luminol anion and HO₂^? to form luminol radical (L^?) and O₂^?. The excited state 3-aminophthalate anion was obtained in the reaction of L^? and O₂^?, which was the emitter (luminophor) in the luminol–H₂O₂ CL reaction system and the maximal emission of the CL spectrum was at 425 nm. The experiments of scavenging oxygen-related radicals were done to confirm these reactive oxygen species participated in the CL reaction. The limits of detection (LOD) (S/N=3) were 8×10^?7 g mL^?1 for furacilin, 8×10^?8 g mL^?1 for furantoin, 4×10^?8 g mL^?1 for furazolidone and 2×10^?7 g mL^?1 for furaltadone. The proposed method was successfully applied to the determination of NFs in feeds and pharmaceutical samples.     

A novel 3D measuring method for discontinuous object by non-integral twin-frequency grating

A new 3D shape measurement method based on non-integral twin-frequency grating projection is proposed. In this paper, the projected composite grating is composed of two sinusoidal gratings, and the quotient of whose frequencies is not an integer. By using appropriate phase-shifting algorithms, two wrapped phases can be obtained from sixteen frames of the distorted grating patterns. In aid of appropriate phase unwrapping method, the unwrapped phase of high frequency fringe is obtained only from the relation of the two wrapped phases by a pixel-to-pixel phase unwrapping technique. Therefore the unwrapped phase of high frequency fringe pattern is independent of the low frequency fringe pattern, different from traditional integral twin-frequency grating projection methods in which the phase unwrapping error of low frequency fringe pattern may be propagated onto the unwrapped phase of high frequency fringe pattern. The new theory proves that the proposed method is applicable to measure discontinuous object, and has considerable measurement accuracy.     

基于贝叶斯方法的时变可靠度分析

针对现役钢筋混凝土桥梁时变可靠度分析的现状,首先根据主观经验信息确定了一个抗力统计参数退化模型,然后结合结构实际检测信息,运用贝叶斯方法综合这两类信息,并进行了推断,从而对模型参数进行了更新,并利用更新后的参数对混凝土模型和钢筋锈蚀模型进行了修正,最后结合已有的荷载效应分析理论,计算时变可靠度,给出了一个计算实例.     

Effects of different nuclear recipients on developmental potential of mouse somatic nuclear transfer embryos

Somatic cell nuclear transfer has been succeeded in procedures of nuclear transfer. One is single nucleartransfer, the other is serial nuclear transfer. Viable animals have been cloned in different species using both me-thods[1—6]. Different nuclear recipients and donors wereused in serial nuclear transfer, namely, transferring thenuclear of reconstructed embryo into enucleated MⅡoocytes[7], transferring the nuclear of reconstructed em-bryos at one cell stage into enucleated zygote[4] and t…     

一种基于C++Builder的过程控制系统设计与实现

详细介绍了一种以C+ +Builder为系统开发平台,利用Matlab作为数学分析、数据处理工具的过程控制系统的设计与实现.该系统不仅充分发挥了C+ +Builder在WIN32系统下快速开发应用程序的强大优势,而且充分利用了Matlab在开发控制算法上长处.这使得开发的工控系统在平台开放、易于扩充、二次开发能力上具有较大优势.