Study of the Electrochemical Behavior of Disperse Blue 1‐Modified Graphite Electrodes. Application to the Flow Determination of NADH

The preparation and the electrochemical study of Disperse Blue 1‐chemically modified electrodes (DB1‐CME), as well as their efficiency for the electrocatalytic oxidation of NADH is described. The proposed mediator was immobilized by physical adsorption onto graphite electrodes. The electrochemical behavior of DB1‐CME was studied with cyclic voltammetry. The electrochemical redox reaction of DB1 was found to be reversible, revealing two well‐shaped pair of peaks with formal potentials 152 and ?42 mV, respectively, (vs. Ag/AgCl/3M KCl) at pH 6.5. The current I_p has a linear relationship with the scan rate up to 800 mV s^?1, which is indicative for a fast electron transfer kinetics. The dissociation constants of the immobilized DB1 redox couple were calculated pK₁=4 and pK₂=5. The electrochemical rate constants of the immobilized DB1 were calculated k₁°=18 s^?1 and k₂°=23 s^?1 (Γ=2.36 nmol cm^?2). The modified electrodes were mounted in a flow injection manifold, poised at +150 mV (vs. Ag/AgCl/3M KCl) and a catalytic current due to the oxidation of NADH was measured. The reproducibility was 1.4% RSD (n=11 for 30 μM NADH) The behavior of the sensor towards different reducing compounds was investigated. The sensor exhibited good operational and storage stability.     

汞离子天然吸附剂

汞离子是现代工业中剧毒的污染物之一,研究者致力于汞离子高效吸附剂的研制已有多年.本文基于国内外最新研究文献,系统论述了汞离子天然吸附剂如壳聚糖、矿物、微生物及其改性材料等的吸附性能,并详细比较了各种吸附剂的优缺点,指出天然吸附剂来源广泛、价格便宜,尤其是修饰后的壳聚糖吸附性能甚至可以和一些合成吸附剂相媲美.在所报道的天然吸附剂中,引入巯基后的戊二醛交联壳聚糖,对初始浓度为500 mg/L的汞离子的吸附容量可达1 604.7mg/g,属已知的汞离子天然吸附剂中之最.天然汞离子吸附剂在工业废水处理中显示出了广阔的应用前景.     

铁粉为原料催化改性铁氧化物的储氢性能

以Fe粉为原料, 以金属Mo, Al和Ni可溶性盐作为添加剂, 通过浸渍法制备单金属添加和双金属添加的改性铁氧化物储氢材料Fe-Mo, Fe-Al, Fe-Mo-Ni和Fe-Mo-Al, 并研究了它们的储氢性能. 结果表明样品Fe-Mo改性效果最好: 如放氢温度由改性前的500 ℃降至改性后的290 ℃左右; 300 ℃时放氢速率最高, 由改性前的低于50 μmol•min^－1• Fe-g^－1到改性后的325 μmol•min^－1•Fe-g^－1 (10次平均); 4.53 wt%的平均实验储氢量与理论值4.8 wt%较接近; 储-放氢循环稳定性随着循环次数的增加呈逐渐增加的趋势. SEM微观结构和BET比表面积分析表明添加剂的种类对样品的改性作用更重要.     

3-乙氧基-4-羟基苯乙醇酸在聚邻甲苯胺-Cu2+膜电极上的电氧化

采用循环伏安法制备了聚邻甲苯胺(POT)膜电极,再以浸泡吸附法在此膜中嵌入Cu2+,制成POT-Cu2+膜电极.研究了POT-Cu2+膜电极对3-乙氧基-4-羟基苯乙醇酸的电氧化行为,并讨论了影响电氧化活性的主要因素.结果表明,50℃下,在含有0.5mol.L-13-乙氧基-4-羟基苯乙醇酸的1.5mol.L-1氢氧化钠溶液中,POT-Cu2+膜电极具有高的电氧化活性和良好的稳定性.将该电极用于3-乙氧基-4-羟基苯乙醇酸电解氧化脱羧制备乙基香兰素,在0.55V(vsSCE)下恒电位电解1h,乙基香兰素的产率可达89%以上,电流效率达97%以上.     

姜黄素及其改性产物与皮胶原作用研究

我国使用天然染料历史悠久,但随着近代化学工业的发展,出现了合成染料,合成染料以其丰富多彩的色彩和优良的染色牢度而得以广泛应用,天然染料则受到冷落.     

LOCAL A PRIORI AND A POSTERIORI ERROR ESTIMATE OF TQC9 ELEMENT FOR THE BIHARMONIC EQUATION

In this paper, local a priori, local a posteriori and global a posteriori error estimates are obtained for TQC9 element for the biharmonic equation. An adaptive algorithm is given based on the a posteriori error estimates.     

On Some Topological Indices Defined via the Modified Sombor Matrix

Let G be a simple graph with the vertex set V={v1,…,vn} and denote by dvi the degree of the vertex vi. The modified Sombor index of G is the addition of the numbers (dvi2+dvj2)−1/2 over all of the edges vivj of G. The modified Sombor matrix AMS(G) of G is the n by n matrix such that its (i,j)-entry is equal to (dvi2+dvj2)−1/2 when vi and vj are adjacent and 0 otherwise. The modified Sombor spectral radius of G is the largest number among all of the eigenvalues of AMS(G). The sum of the absolute eigenvalues of AMS(G) is known as the modified Sombor energy of G. Two graphs with the same modified Sombor energy are referred to as modified Sombor equienergetic graphs. In this article, several bounds for the modified Sombor index, the modified Sombor spectral radius, and the modified Sombor energy are found, and the corresponding extremal graphs are characterized. By using computer programs (Mathematica and AutographiX), it is found that there exists only one pair of the modified Sombor equienergetic chemical graphs of an order of at most seven. It is proven that the modified Sombor energy of every regular, complete multipartite graph is 2; this result gives a large class of the modified Sombor equienergetic graphs. The (linear, logarithmic, and quadratic) regression analyses of the modified Sombor index and the modified Sombor energy together with their classical versions are also performed for the boiling points of the chemical graphs of an order of at most seven.     

Ultrasensitive Simultaneous Detection of Multiple Rare Modified Nucleosides as Promising Biomarkers in Low-Put Breast Cancer DNA Samples for Clinical Multi-Dimensional Diagnosis

Early cancer diagnosis is essential for successful treatment and prognosis, and modified nucleosides have attracted widespread attention as a promising group of cancer biomarkers. However, analyzing these modified nucleosides with an extremely low abundance is a great challenge, especially analyzing multiple modified nucleosides with a different abundance simultaneously. In this work, an ultrasensitive quantification method based on chemical labeling, coupled with LC-MS/MS analysis, was established for the simultaneous quantification of 5hmdC, 5fdC, 5hmdU and 5fdU. Additionally, the contents of 5mdC and canonical nucleosides could be obtained at the same time. Upon derivatization, the detection sensitivities of 5hmdC, 5fdC, 5hmdU and 5fdU were dramatically enhanced by several hundred times. The established method was further applied to the simultaneous detection of nine nucleosides with different abundances in about 2 μg genomic DNA of breast tissues from 20 breast cancer patients. The DNA consumption was less than other overall reported quantification methods, thereby providing an opportunity to monitor rare, modified nucleosides in precious samples and biology processes that could not be investigated before. The contents of 5hmdC, 5hmdU and 5fdU in tumor tissues and normal tissues adjacent to the tumor were significantly changed, indicating that these three modified nucleosides may play certain roles in the formation and development of tumors and be potential cancer biomarkers. While the detection rates of 5hmdC, 5hmdU and 5fdU alone as a biomarker for breast cancer samples were 95%, 75% and 85%, respectively, by detecting these three cancer biomarkers simultaneously, two of the three were 100% consistent with the overall trend. Therefore, simultaneous detection of multiple cancer biomarkers in clinical samples greatly improved the accuracy of cancer diagnosis, indicating that our method has great application potential in clinical multidimensional diagnosis.     

纳米铂微粒修饰电极上甲醛电催化氧化的电位振荡和电流振荡

通过阴极还原-阳极氧化法制备了钛基纳米铂微粒修饰电极, 扫描电镜观察发现, 分布于钛基体表面的氧化钛膜三维网状孔道中的纳米铂微粒具有高度分散状态. 采用多种电化学手段在该电极上不仅观察到甲醛在恒电流条件下产生的电位振荡, 而且在循环伏安和恒电位两种条件下均观察到强烈的电流振荡, 这进一步证明高度分散的纳米铂微粒使电极的催化活性大大提高, 促进了甲醛及其毒化中间产物的电催化氧化过程, 从而有利于电极上电化学振荡的产生. 研究结果还表明, 甲醛底物浓度、硫酸介质浓度、恒电位或恒电流大小等多种因素对振荡强度、范围或类型会产生规律性的影响.