二维映射神经元模型中的相干双共振

在具有稳定次阈值振荡特性的二维映射神经元模型中, 研究了在没有外界输入信号时噪声对体系动力学的影响. 通过数值计算发现了当体系的确定性动力学处于静息状态时, 噪声可以诱导出神经元膜电位的随机振荡, 而且随着噪声强度的变化, 这种振荡的相干性具有两个极大值. 另外我们还研究了当体系的确定性动力学处于稳定次阈值振荡及神经脉冲状态时的噪声效应, 结果表明噪声对体系动力学的影响与其确定性动力学的分岔特性密切相关.     

一个广义扰动mKdV耦合系统2极孤子的近似解

采用了一个简单而有效的技巧,研究了一类扰动mKdV耦合系统.首先利用变分迭代方法求解一个相应的复值函数微分方程2-极孤子的近似解.然后得到了原扰动mKdV耦合系统2-极孤子的近似解. 关键词： 孤子 扰动mKdV方程 变分迭代     

MgO/NaY催化剂上葡萄糖水中异构制取果糖的研究

The MgO/NaY catalysts prepared by impregnation method were used for the conversion of glucose to fructose in water medium.The effects of MgO loading,reaction temperature,glucose concentration and reaction time on the catalytic performance for the reaction were studied.The activity testing results indicated that fructose could be generated effectively by controlling the components of the catalyst and reaction conditions.The maximal fructose yield of 33.8% with the selectivity of 67.3% was achieved over the 10% MgO/NaY catalyst at 100 ℃ for 2 h.Moreover,the catalysts were characterized by XRD,BET,and CO₂-TPD techniques.The structural property of NaY with higher surface area facilitated glucose conversion,and the modulated basicity of the catalyst with MgO addition contributed to the formation of fructose in the tautomerization of aldose to ketose.     

Direct electron transfer of Mb on chitosan/single-wall carbon nanotubes film modified Au electrode and its interaction with cimetidine

Three methods were used to immobilize myoglobin (Mb) on chitosan/single-wall carbon nanotubes (SWNTs) film, and direct electrochemistry of the immobilized Mb was extensively investigated. Immobilized Mb displayed a couple of stable and well-defined redox peaks with the formal potential (E’) is at about −0.27 V (vs. SCE) in 0.1 M phosphate buffer solution (pH 7.0). The E′ was shifted linearly with pH in the range of 3.0 to 9.0 with a slope of −54.1 mV pH⁻¹, denoting that one-electron accompanies with one-proton transfer in electrode reaction process. The FT-IR spectroscopy and UV-vis spectroscopy showed that Mb on the film retained its secondary structure similar to its native state. The experimental results demonstrated that the immobilized Mb exhibited excellent electrocatalytic activity to reduction of cimetidine with a significant lowering of overpotential. The electrocatalytic current was proportional to the concentration of cimetidine over the range from 9.80 × 10⁻⁶ to 1.1 × 10⁻⁴ M; the detection limit is 8.40 × 10⁻⁶ M (signal-to-noise ratio of 3). The proposed method exhibits good sensitivity, stability and reproducibility. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 2, pp. 235–243. The text was submitted by the authors in English     

Some remarks on pseudo-umbilical totally real submanifolds in a complex projective space

This paper studies the relationship between the pseudo-umbilical totally real submanifolds and the minimal totally real submanifolds in a complex projective space. Two theo- rems which claim that some types of pseudo-umbilical totally real submanifolds must be minimal submanifolds are proved.     

Study on electrochemical behavior of tryptophan at a glassy carbon electrode modified with multi-walled carbon nanotubes embedded cerium hexacyanoferrate

Electrochemical behavior of cerium hexacyanoferrate (CeHCF) incorporated on multi-walled carbon nanotubes (MWNTs) modified GC electrode is investigated by scanning electron microscopy (SEM) and electrochemical techniques. The CeHCF/MWNT/GC electrode showed potent electrocatalytic activity toward the electrochemical oxidation of tryptophan in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of 240 mV. The anodic peak currents increased linearly with the concentration of tryptophan in the range of 2.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M with a detection limit of 2.0 × 10⁻⁸ M (at a S/N = 3). And the determination of tryptophan in pharmaceutical samples was satisfactory.     

S-甘油醛缩丙酮的合成及其Wittig反应

以L-抗坏血酸为原料合成了S-甘油醛缩丙酮;研究了S-甘油醛缩丙酮的Wittig反应立体选择性.     

Fluorescence-detecting cationic surfactants using luminescent CdTe quantum dots as probes

A novel fluorescence quenching method for the determination of cationic surfactants (CS), specifically cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and cetylpyridinium chloride (CPC), has been developed using water-soluble luminescent CdTe quantum dots (QDs) modified with thioglycolic acid (TGA). The possible interference from heavy and transition metals (HTM) has been efficiently eliminated through simple sample treatment with mercapto cotton made in-house. Under optimum conditions, the extent of fluorescence quenching of CdTe QDs is linearly proportional to the concentration of CS from 2.0 × 10⁻⁷ to 7.0 × 10⁻⁶ mol L⁻¹ with a detection limit of 5.0 × 10⁻⁸ mol L⁻¹. The relative standard deviation for 1.0 × 10⁻⁶ mol L⁻¹ CTAB is 2.5% (n = 6). The proposed method exhibits high sensitivity and selectivity and furthermore avoided the use of toxic organic solvents and tedious solvent extraction procedures. It has been applied to the determination of trace CS in natural river water and commodity samples with satisfactory results. Potential interference from heavy and transition metals is eliminated during photoluminescence detection of CS through simple sample pre-treatment with mercapto cotton     

[SiNi(H2O)W11O39]6-多层组装膜修饰电极及其电化学行为

采用电化学生长法制备包含杂多酸[SiNi(H2O)W11O39]6-(SiNiW11)和聚合物阳离子PDDA的多层膜修饰电极, 利用循环伏安法研究其电化学行为、 pH的影响及其对BrO3-和NO2-体系还原的电催化性能;并对多层膜电化学过程机理进行了初步探讨. 结果表明: 多层膜的增长均匀, 峰电流随层数的增加而增加;多层膜的峰电流随扫速的增加而增加;还原峰的峰电位随pH的增加而负移.