Mass transfer to horizontal gas-generating electrodes

Mass transfer to a horizontal electrode during electrolytic evolution of oxygen and hydrogen at current densities of 100 to 10 000 A/m² is studied. The mass transfer intensity is evaluated from the diffusion layer thickness, which varies from 60 to 5 μm at such current densities. Calculations show that the decrease in the diffusion layer thickness is due to bubbles with a stationary interphase surface crossing the diffusion layer. During the hydrogen evolution, the diffusion layer thickness is nearly the same for vertical and horizontal electrodes. During the oxygen evolution, the diffusion layer is much thinner for a horizontal electrode. Additional decrease of the diffusion layer thickness during the evolution of oxygen is associated with the lesser solution density in the near-electrode layer and with its transport away by means of natural convection.     

电化学合成聚苯胺粉末电极的电化学行为研究

我们曾用慢速动电位扫描法研究化学合成聚苯胺粉末的电化学行为.本文对恒电位电解合成聚苯胺粉末进行了研究.用这种方法制备的粉末由于合成溶液中不含氧化剂因而纯度高.本文还报导了这种聚苯胺粉末电极的交流阻抗测量结果.交流阻抗法曾用于聚苯胺膜的电导和化学合成聚吡咯的电阻测定. 所用盐酸、氟硼酸、硅氟酸、苯胺均为分析纯;苯胺经常压蒸馏提纯;硫酸为超纯;磷酸为分析纯;高氯酸为优级纯.溶液皆用两次蒸馏水配制.     

Detecting DNA Damage with a Silver Solid Amalgam Electrode

Mercury electrodes modified with supercoiled (sc) DNA have been used as highly sensitive tools for the detection of DNA strand breaks or as sensors for DNA cleaving substances. In this paper we show that silver solid amalgam electrode (AgSAE), in connection with alternating current voltammetry, provides similar information about DNA damage as the hanging mercury drop electrode. The AgSAE can be used for the detection of enzymatic or chemical DNA cleavage in solution or at the electrode surface. AgSAE modified with scDNA can be utilized as a sensor for DNA nicking substances.     

1H-CRAMPS Solid-State NMR and X-Ray Crystal Studies of Inclusion Complexes Formed from 3,3′-bis(9-Hydroxy-9-fluorenyl)-2,2′-binaphthyl Hosts with Acetone

The crystal structures of inclusion compounds of 3,3-bis(9-hydroxy-9-fluorenyl)-2,2-binaphthyl host (1) and its chloro (2) or bromo (3) derivatives substituted in 2,7-positions of the fluorene units with acetone guests (1A–3A) were determined by X-ray studies as well as by ¹H-CRAMPS solid-state NMR. Using this NMR technique allows identification of differently bound guest molecules due to their different chemical shifts caused by the influence of the ring current effects of the host aryl units.     

Dual microband electrodes: current distributions and diffusion layer ‘titrations’. Implications for electroanalytical measurements

The simulation of transport to double microband electrodes in generator–collector mode is reported focusing especially on the ‘titration curve’ approach to electroanalysis in which a titrant is electrogenerated from a redox active precursor on the generator electrode and reacts homogeneously with the target analyte. The current on the detector electrode reflects the amount of titrant ‘surviving’ passage between the two electrodes. The form of the titration curve – plots of detector current as a function of generator current – is shown to be highly sensitive to the electrode kinetics of the redox couple driven at the generator electrode. Accordingly the naïve use of such methodology for analysis without accompanying simulation and kinetic analysis is fraught with danger. Use of the conformal mapping approach in combination with the ADI method for investigation of the ‘titration’ current distributions at the double band system gives fast and precise simulation of this and similar problems. Convergence analysis is described which allows for the automatic selection of the simulation grid size so as to obtain a chosen accuracy (for example 1%) of the current for all experimentally meaningful values of the geometrical and physico-chemical parameters of the system to be investigated.     

三角波交流示波极谱的研究(Ⅰ)——示波极谱图的性质

用三角波电流代替正弦波电流,进行交流示波极谱滴定,所得示波极谱图与正弦波结果相似。对一些离子的滴定表明,两法所得结果均在定量分析允许误差范围以内。报道了三角波交流示波极谱图的一些性质。     

Effects of Cathode and Anode on Deposition of Trimethylsilane in Glow Discharge

DC cathodic polymerization of trimethylsilane (TMS) was carried out in plasma reactors with and without using anode assembly. In DC cathodic polymerization, the TMS plasma polymers are mainly deposited on the cathode (substrate) surface. As a result, fast deposition of TMS plasma polymers was easily achieved in DC cathodic polymerization as compared with AF or RF plasma polymerization. DC cathodic polymerization without using anode assembly has its advantageous features that the size and number of substrates (as cathodes) are not restricted by the size and the location of anode assembly. It was found that the maximum deposition rate on the cathode surfaces was obtained without anode assembly. The DC cathodic polymerization of TMS was conducted also in a large volume reactor with multiple cathodes (substrates). The same deposition mechanisms for DC cathodic polymerization with a single cathode also apply to the multiple cathodes. Uniform deposition on each cathode could be obtained with appropriate spacing of multiple cathodes and by adjusting the operational parameters, which are based on the current density and the system pressure.     

恒电流库仑法测定基准试剂三氧化二砷的含量

用恒电流库仑法测定基准试剂三氧化二砷的含量，以恒电流通过含有碘化钾，基准试剂三氧化二砷试样的弱碱性水溶液，利用工作电极铂阳极上电生滴定剂I2与亚砷酸盐定量反应，以死停终点法确定滴定终点，测量出电解电流和电解时间，根据法拉第电解定律并利用EXCEL计算出基准试剂三氧化二砷的含量。方法的回收率为100％。     

色谱技术在中药指纹图谱研究中的应用

 介绍了气相色谱、高效液相色谱、超临界流体色谱和高速逆流色谱等几种色谱技术在中药指纹图谱研究中的应用现状,以及使用模糊聚类分析和人工神经网络分析指纹图谱对中药进行模式识别和质量鉴定的方法。     

Thermally stimulated depolarization currents of tactic polymethyl methacrylates and their mixtures

Summary Thermally stimulated depolarization currents (TSDC) of atactic (a), syndiotactic (s) and isotactic (i) PMMA and mixtures ofs- andi-PMMA were measured. In pure tactic PMMA, TSDC peak was obtained at a temperature corresponding to the glass transition temperature of each PMMA. TSDC of mixtures isolated as precipitates from 1/1 and 1/2 (i/sweight ratio) mixed solutions showed a peak which can be attributed to the glass transition temperature of the stereocomplex. TSDC of original l/1 mixture showed two peaks which are ascribed to the glass transition temperature of residual i-PMMA and the stereocomplex. The results suggests that stereocomplex formation occurs ini/s weight ratio of 1/2 independent of the way of preparation.With 9 figures and 1 table