Potential response in the uncatalyzed bromate oscillatory system

The potential response of the platinum indicator electrode in the uncatalyzed bromate oscillator (UBO) with three different substrates, namely gallic acid (GA), pyrogallol (PG) and veratraldehyde (VA) has been analyzed. The large amplitude oscillations obtained with a Pt electrode are due to the sequential response of the indicator electrode to the varying concentration ratios of the redox couples present in the reaction mixture.     

All Solid‐State pH Electrode Based on Titanium Nitride Sensitive Film

Titanium nitride was used as pH‐sensitive material to fabricate all solid‐state pH electrode. The fabrication and the response performance of the pH electrode were described in the paper. The TiN film electrode showed a linear response in the pH range of 2–12 with a near‐Nenstian response (?55 mV/pH). The response time was within 1 min, and the electrode had good reproducibility, stability and low sensitivities for different species. Compared with the glass pH electrode, the electrode exhibited some advantages, for example, without activation, rapid response and high mechanical strength. In addition, the electrode performed excellently in a corrosion medium containing F^?(1 M). Electrochemical behaviors of TiN electrode in Britton‐Robinson buffers were studied with Electrochemical Impedance Spectroscopy (EIS).     

Photocrosslinking of copolymers of vinyloxyethyl methacrylate–styrene initiated by sulfonium salts. I. Transient species formed on photolysis of sulfonium salt

Benzyl cation was detected by transient absorption spectroscopy with a spectroscopic multichannel analyzer on pulse excitation (fourth harmonic of Nd:YAG laser, 266 nm; 10 ns fwhm) of benzyl(4-hydroxyphenyl) methylsulfonium hexafluoroantimonate(BSS) in 1,2-dichloroethane (EDC). The benzyl cation was long-lived (lifetime, 59 ms) at room temperature and quenched by a vinyl ether compound. The formation of the benzyl cation as active species on photolysis of BSS is in contrast to the formation of Brønsted acids in other sulfonium salts so far reported. © 1992 John Wiley & Sons, Inc.     

Electron capture detector performance parameters in view of the response presentation forms

Summary Four most frequently used presentation forms of the ECD response are described. Equations describing the dependence of the sensitivity, linearity and minimum detectable concentration of the ECD working under constant frequency mode of operation on the pulse period are derived from Wenthworth’s kinetic model for all four forms mentioned above. The forms presented are compared on the basis of equations derived. Results of the calculations are given and some predictions are experimentally tested for sulphur hexafluoride. Good agreement was found between the predicted and observed relationships. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

High Performance Varistor Discs Obtained from Chemically Synthesized Doped Zinc Oxide Powder

The ceramic microstructure, the chemical homogeneity of specific dopants and the mechanical integrity of a varistor disc are critical parameters in determining the transient voltage suppression features of these devices. The material properties and overall quality of the starting ceramic powders used to produce such components are essential in achieving the desired properties. The present work describes a novel chemical method developed to produce doped zinc oxide powders and an industrial scale manufacturing process for the production of final varistor blocks for surge arrester applications. The results are compared with those obtained when using standard varistor powder made by the mixed oxide route is used. All the fundamental electrical properties of the discs have been determined and correlated with the relevant manufacturing steps.     

Reaction of sulphate radical anion (SO<Superscript>.</Superscript><Subscript>4</Subscript><Superscript>-</Superscript>) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study

Reactions of sulphate radical anion (SO·₄ ^-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·₄ ^- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH^- leading to the formation of OH adducts.     

STUDIES ON PREPARATION OF INACTIVATED VACCINES FROM CELL CULTURES OF MINK ENTERITIS VIRUS (MEV) AND THEIR IMMUNITY

In this paper, superhigh reproductive rate strains of MEV with titre more than HA8192* or TCID50 log9.7 10 have been achieved both by cultivation in cell lines with different susceptibility to MEV and by isolating and identifying in field by the author. The systematic tests proved that S18 and L12 strains of MEV are the best strains for vaccine preparation. In this study, the best means for the tissue cultivation of MEV and the most advanced technological process for the production and detection of serum-free cell-cultured MEV fluids with super-high HA titre in batches in large quantities have been established for the first time. Optimum conditions for MEV inactivation were determined, and safe and effective inactivated vaccines with mineral oil or A1(OH)3 gel adjuvant were successfully prepared with serum-free cell-cultured MEV fluids. Both vaccines with different adjuvants can be manufactured in batches in large quantities and have been widely used all over China since 1986. The change laws of the imm     

Effect of enzyme concentration on the dynamic behavior of a membrane-bound enzyme system

The dynamic behavior of the reaction-diffusion system, composed of glucose oxidase (EC 1.1.3.4) immobilized at a uniform concentration in a membrane, used as a glucose electrode is represented by a diffusion equation with a nonlinear reaction-term in one-dimensional space. The mathematical model is analyzed by computer simulation, that is, numerical integration of the equation under various initial and boundary conditions, to examine the effect of enzyme concentration on the response characteristics (responsiveness and linearity in response) of the electrode. The analysis of the responses of the system to stepwise changes in the boundary value (glucose concentration in simple solution) infers that the enzyme concentration governs the patterns of the spatial distributions of the substrates (glucose and dissolved oxygen) in steady states and transient responses. It is also revealed that the response characteristics of the electrode are optimized with concentration of immobilized enzyme and that the system establishes the steady states at the same spatial distributions of the substrates, regardless of the boundary value. The diffusion of the substrates and the oxygen concentration also have significant effects on the response characteristics of the electrode.     

Development of a systems analysis approach for resolving the structure of biodegrading soil systems

An experimental and mathematical method is developed for the microbial systems analysis of polyaromatic hydrocarbon (PAH)-degrading mixed cultures in PAH-contaminated “town gas” soil systems. Frequency response is the primary experimental and data analysis tool used to probe the structure of these complicated systems. The objective is to provide a fundamental protocol for evaluating the performance of specific mixed microbial cultures on specific soil systems by elucidating the salient system variables and their interactions. Two well-described reactor systems, a constant volume stirred tank reactor (CSTR) and a plug flow differential volume reactor, are used in order to remove performance effects that are related to reactor type as opposed to system structure. These two reactor systems are well-defined systems that can be described mathematically and represent the two extremes of one potentially important system variable, macroscopic mass transfer. The experimental and mathematical structure of the protocol is described, experimental data is presented, and data analysis is demonstrated for the stripping, sorption, and biodegradation of napththalene.     

A new dodecylsulfate-selective supported liquid membrane electrode based on its N-cetylpyridinium ion-pair

A supported liquid and a poly(vinyl chloride) (PVC)-based membrane selective for dodecylsulfate (DS⁻) ion are described. The active element is a membrane containing a dissolved ion association complex of DS⁻ with cetylpyridinium (CP⁺) cation. The supported liquid membrane electrode (acetophenone as solvent) showed a Nernstian response towards the DS⁻ anion over the concentration range of sodium dodecylsulfate (SDS) from 8.3×10⁻³ to 1.0×10⁻⁶ mol dm⁻³ at 25 °C. The proposed electrode also showed a super-Nernstian potential response (108±2 mV decade⁻¹) at low concentrations (1.0×10⁻⁹ to 1.0×10⁻⁶ mol dm⁻³). Moreover, this electrode showed good selectivity and precision (R.S.D.?2.0%), and was usable within the pH range 4.0-6.8. The proposed electrode revealed a lower limit of detection of 6.3×10⁻⁷ mol dm⁻³ and improved selectivity in comparison with the some previously reported DS⁻ ion selective electrodes. The isothermal temperature coefficient of this electrode amounted to −0.001 V °C⁻¹. The liquid membrane electrode may find application in the direct determination of SDS by the standard addition method at pH 5.0, and in the physicochemical studies of surfactant solutions.