度量射影的Lipschitz连续选择

It has shown that, for Lipschitz continuous metric projections, it has a Lips-chitz continuous selection for l-Chebyshev subspace and, for each subspace M which is ismorphism to a Hilbert space ,P_M admits a selection s which is locally Lipschitz continuous with index 1/2.     

降低聚氯乙烯膜黄连素选择性电极检出限的新方法

PVC药物选择性电极的检出限主要是由膜中活性物质的溶解和内参比溶液中被测离子在膜中的迁移所决定的。为了减少这两种不利因素的影响 ,采用内参比为含可乐定的氯化钠溶液的可乐定选择性电极测定黄连素。测定的线性范围为 1.0× 10 - 4～ 1.0× 10 - 8mol L ,平均斜率为 5 8.6mV decade ;检出下限为 2 .5×10 - 9mol L ,比已报道的检出下限要低 2～ 3个数量级。电极的选择性明显提高 ,选择性系数的测定更加可靠真实 ,并获得良好的重现性和稳定性。以标准加入法测定回收率 ,结果令人满意。     

LC–ESI–MS Determination of 20 Free Amino Acids in Tibetan Medicine Gentiana dahurica with Pre-Column Fluorescence Derivatization

Concentrations of 20 free amino aicds (FAAs) in a famous Tibetan medicine Gentiana dahurica was first investigated using 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) as the pre-column fluorescence derivatization reagent by reversed-phase high performance liquid chromatography (RP-LC). 20 amino acid derivatives (AAD) were separated on a Hypersil BDS C₁₈ column with a good baseline resolution within 65 min. Identification of 20 AAD was by online post-column mass spectrometry with an electrospray ionization (ESI) source. The validation of the method was examined by linearity, repeatability, and detection limits. Most linear correlation coefficients for AAD were >0.9990, and detection limits (at signal-to-noise of 3:1) were 6.5–178.2 fmol. There were 18 FAAs found in G. dahurica, of which seven FAAs were necessary to the people’s health and related to the treatment of liver and gall disease. Variation of concentrations of the 20 FAAs showed geographical distribution difference among populations. Meanwhile a stable genetic diversity of FAAs composition of G. dahurica was also revealed at the species level. Results of the present study proved that the established method was rapid and reproducible for further separation and determination of FAAs in more medicinal plants.

     

Self‐assembly of H‐bonded side‐chain and cross‐linking copolymers containing diblock‐copolymeric donors and single/double H‐bonded light‐emitting acceptors

A series of diblock‐copolymers were synthesized through anionic polymerization of styrene and tert‐butyl methacrylate (tBuA) with different monomer ratios, and analogous block‐copolymeric derivatives (PS‐b‐PAA)s with monofunctional carboxylic acid groups were obtained by further hydrolyzation as hydrogen‐bonded (H‐bonded) proton donors. Via H‐bonded interaction, these diblock‐coplymeric donors (PS‐b‐PAA)s were incorporated with luminescent mono‐pyridyl/bis‐pyridyl acceptors to form single/double H‐bonded supramolecules, that is, H‐bonded side‐chain/cross‐linking copolymers, respectively. The supramolecular architectures formed by donor polymers and light‐emitting acceptors were influenced by the ratio of acid blocks in the diblock copolymeric donors and the type of single/double H‐bonded light‐emitting acceptors. Their thermal and luminescent properties can be adjusted by H‐bonds, and more than 100 nm of red‐shifted photoluminescence (PL) emissions were observed, which depend on the degrees of the H‐bonding interactions. Self‐assembled phenomena of amphiphilic dibolck copolymers and their H‐bonded complexes were confirmed by TEM micrographs, and supramolecular microphase separation of spherical micelle‐like morphology was demonstrated to affect the photophysical properties. Polymer light‐emitting diode (PLED) devices containing H‐bonded complexes showed electroluminescence (EL) emissions of 503–560 nm under turn‐on voltages of 7.5–9.0 V, maximum power efficiencies of 0.23–0.37 cd/A (at 100 mA/cm²), and maximum luminances of 318–519 cd/m² (around 25 V). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4685–4702, 2009     

具周期输入的有限连续分布时滞神经网络周期解的全局指数稳定性

在去掉对激励函数有界、连续可导、平均时滞有界的条件下,仅要求激励函数满足Lip-schitz条件和连接权矩阵之间的关系是一个M-矩阵的情形下,利用重合度理论、Dini导数等知识得出了具周期输入的有限连续分布的一类细胞神经网络周期解的存在性.利用Dini导数和不等式分析技术在同样条件下得出了周期解的指数稳定性.推广和改进了前人的结论.并举例说明了所得定理的有效性.     

Paley‐Wiener‐Type theorems for the Clifford‐Fourier transform

In the framework of Clifford analysis, we consider the Paley‐Wiener type theorems for a generalized Clifford‐Fourier transform. This Clifford‐Fourier transform is given by a similar operator exponential as the classical Fourier transform but containing generators of Lie superalgebra.     

Dissipativity and synchronization control of fractional‐order memristive neural networks with reaction‐diffusion terms

This paper deals with the dissipativity and synchronization control of fractional‐order memristive neural networks (FOMNNs) with reaction‐diffusion terms. By means of fractional Halanay inequality, Wirtinger inequality, and Lyapunov functional, some sufficient conditions are provided to ensure global dissipativity and exponential synchronization of FOMNNs with reaction‐diffusion terms, respectively. The underlying model and the obtained results are more general since the reaction‐diffusion terms are first introduced into FOMNNs. The given conditions are easy to be checked, and the correctness of the obtained results is confirmed by a living example.     

Synthesis and self-assembly behavior of thermoresponsive triblock copolymer

Block copolymers comprising thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and hydrophobic poly(n-butyl acrylate) (PBA) blocks, were synthesized using the reversible addition-fragmentation chain transfer polymerization (RAFT), their thermosensitive behavior was studied by ultraviolet spectrophotometer (UV) and dynamic light scattering (DLS). The lower critical solution temperature (LCST) was strongly correlated to the hydrophobic/hydrophilic ratio of the copolymers. Their micellization and self-assembly behavior in dilute aqueous solution were studied by surface tension (SFT), DLS and TEM. The resulting block copolymers reversibly formed or deformed micellar assemblies during their LCSTs. The critical micelle concentration (CMC) was controlled by the composition of PBA and PNIPAM, indicating the successful formation of the block copolymers.     

Determination of phthalate esters in liquor samples by vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquid microextraction followed by GC–MS

A novel method using vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquid microextraction has been developed for the extraction of phthalate esters (PAEs) in Chinese liquor samples prior to analysis by GC–MS. In the proposed method, a high‐density extraction solvent (carbon tetrachloride) was dispersed into samples with the aid of a surfactant (Triton X‐100) and vortex agitation, resulting in a short extraction equilibrium (30 s). After centrifugation, a single microdrop of solvent was easily collected for GC–MS analysis. Key factors that affected the extraction efficiency were optimized. Under the optimum conditions, linearity was found in the range from 0.05 to 50 μg/L. Coefficients of determination varied from 0.9938 to 0.9971. LODs, based on an S/N of 3, ranged from 4.9 to 13 ng/L. Enrichment factors varied from 140 to 184. Reproducibility and recoveries were assessed by testing a series of three liquor samples that were spiked with different concentration levels. Finally, the proposed method was successfully applied to the determination of PAEs in 16 Chinese liquor samples. In this work, high‐density‐solvent vortex‐assisted surfactant‐enhanced‐emulsification liquid–liquid microextraction was applied for the first time for the extraction of PAEs in Chinese liquor samples and was proved to be simple, rapid, and sensitive.