Sensitive voltammetric determination of baicalein at DNA Langmuir-Blodgett film modified glassy carbon electrode

The present paper describes to modify a double stranded DNA-octadecylamine (ODA) Langmuir-Blodgett film on a glassy carbon electrode (GCE) surface to develop a voltammetric sensor for the detection of trace amounts of baicalein. The electrode was characterized by atomic force microscopy (AFM) and cyclic voltammetry (CV). Electrochemical behaviour of baicalein at the modified electrode had been investigated in pH 2.87 Britton-Robinson buffer solutions by CV and square wave voltammetry (SWV). Compared with bare GCE, the electrode presented an electrocatalytic redox for baicalein. Under the optimum conditions, the modified electrode showed a linear voltammetric response for the baicalein within a concentration range of 1.0 × 10⁻⁸-2.0 × 10⁻⁶ mol L⁻¹, and a value of 6.0 × 10⁻⁹ mol L⁻¹ was calculated for the detection limit. And the modified electrode exhibited an excellent immunity from epinephrine, dopamine, glucose and ascorbic acid interference. The method was also applied successfully to detect baicalein in the medicinal tablets and spiked human blood serum samples with satisfactory results.     

Amide and Acyl‐Hydrazine Functionalized Calix[4]arenes as Carriers for Hydrogen Phosphate Selective Electrodes

Anion‐selective solvent polymeric membrane based on hydrogen bond‐forming, neutral ionophores with amide or acyl‐hydrazine groups are described. The use of the two calix[4]arenes results in anion‐selective electrodes with a selectivity for phosphate. The electrodes of the optimum characteristic have the composition of 1 wt% ionophore, 66 wt% o‐NPOE, 33 wt% poly (vinyl chloride) (PVC) and TDMACl (15 or 30 mol% relative to the ionophore 1 and 2 , respectively). The optimized membrane electrodes show Nernstian responses towards monohydrogen phosphate (?29.1 and ?29.3 mV/decade) based on ionophore 1 and 2 , respectively, in a wide concentration range (1.0×10^?5 to 1.0×10^?2 or 1.0×10^?5 to 1.0×10^?1 M). The selectivity coefficients are determined with the fixed interference method and the activity ratio method. The electrodes display an anti‐Hofmeister series selectivity pattern and highly selective for HPO₄^2? over Cl^?, Br^?, CH₃COO^?, NO₃^? and SO₄^2?. The lifetime of the electrodes is at least 1 month and their response time is found to be 25 s. The proposed sensors could be put to analytical use both by direct potentiometry as well as potentiometric titration.     

离子交换反应准静态平衡

本文系统地讨论了二元体系和多元体系的离子交换平衡。离子交换反应是复相反应。固相中的离子活度系数是解决交换反应平衡问题的关键。     

一类离散m点边值问题正解的存在性与多重性

本文运用锥上的不动点理论,得到了一类离散多点边值问题的一个正解及两个正 解存在性.     

Determination of neurotransmitters in PC 12 cells by microchip electrophoresis with fluorescence detection

A sensitive fluorescence detection system with an Hg-lamp as the excitation source and a photon counter as the detector for microchip CE (MCE) has been developed. O-Phthaldialdehyde (OPA, lambda(ex) = 340 nm) was employed to label the catecholamine neurotransmitters such as dopamine (DA), norepinephrine (NE), and amino acid neurotransmitters including alanine (Ala), taurine (Tau), glycine (Gly), glutamic acid (Glu), and aspartic acid (Asp). The separation of seven derivatized neurotransmitters was successfully performed in MCE and the detection limits (S/N = 3) for DA, NE, Ala, Tau, Gly, Glu, and Asp were 0.85, 0.49, 0.23, 0.15, 0.13, 0.18, and 0.29 fmol, respectively. The system was then successfully applied for separation and determination of neurotransmitters in rat pheochromocytoma (PC 12) cells, and the average amounts of analyte per cell from a cell population were 2.5 fmol for DA, 3.3 fmol for Ala, 8.2 fmol for Tau, 4.0 fmol for Gly, and 1.9 fmol for Glu, respectively. By single-cell injection mode, electrophoresis separation and quantitative measurement of Glu in individual PC 12 cells was obtained. The average value of Glu per cell from single PC 12 cells analysis was found to be 3.5 +/- 3.1 fmol.     

Investigation on the preparation and chromatographic behavior of a new para-tert-butylcalix[4]arene-1,2-crown-4 stationary phase for high performance liquid chromatography

In the present work, a new para-tert-butylcalix[4]arene-1,2-crown-4 bonded silica stationary phase (CBS4-4) was synthesized, structurally characterized, and employed to separate polycyclic aromatic hydrocarbons (PAHs), phenols, aromatic amines, benzoic acid and its derivatives. The chromatographic behaviors of the prepared stationary phase were investigated and compared with ODS. The effects of methanol concentrations on the retention index show that CBS4-4 exhibits high selectivity for the above analytes. The separation mechanisms based on the different interactions between calixarene and the analytes were discussed. With the assistance of quantum chemistry calculation, the interaction Gibbs free energy change ΔG_solv (in the mobile phase) of p, m and o-phenylenediamine positional isomers and para-tert-butylcalix[4]arene-1,2-crown-4 were obtained. The ΔG_solv values were consistent with the retention behavior of p, m and o-phenylenediamine on the CBS4-4. According to the chromatographic data, it can be concluded that the selectivity of CBS4-4 for analytes is mainly ascribed to hydrophobic interaction, accompanied by other effects such as hydrogen bonding interaction, π-π and inclusion interaction. The CBS4-4 column has been successfully employed for the analysis of benzoic acid in Sprite drink.     

Chaos synchronization in general complex dynamical networks with coupling delays

On the basis of Lyapunov stability theory, chaos synchronization of a general complex dynamical network with coupling delays is investigated. Some delay-independent and delay-dependent criteria for exponential synchronization are derived via adopting the free weighting matrix approach; these are less conservative than those previously reported. As an example, the upper bound of the coupling delay for a Duffing system is obtained, and is larger than those reported previously. Finally, some simulation results obtained with different outer-coupling matrices are given to demonstrate the effectiveness of the results that we obtained, and these are compared with existing conclusions to show the advantage of our results.     

爆破震动对某边坡稳定性影响的数值模拟

爆破震动是影响边坡稳定性的一个重要因素之一。结合实际工程文章利用了拉格朗日有限差分法FLAC程序对爆破震动作用下某边坡进行了数值模拟。讨论了利用FLAC进行边坡动力分析时设置边界条件设置、动力时程的合成、输入以及转化,阻尼的合理选取。从位移场和速度场进行了详细的动力分析。获得该边坡爆破震动特征及位移场、振动速度场的变化规律。研究成果对保证边坡安全具有较好的指导作用。