Polyanion-Polykation-Wech-selwirkung. 2. Mitt

Ohne Zusammenfassung     

Isometric graphing and multidimensional scaling for reaction-diffusion modeling on regular and fractal surfaces with spatiotemporal pattern recognition

Heterogeneous surface reactions exhibiting complex spatiotemporal dynamics and patterns can be studied as processes involving reaction-diffusion mechanisms. In many realistic situations, the surface has fractal characteristics. This situation is studied by isometric graphing and multidimensional scaling (IGMDS) of fractal surfaces for extracting geodesic distances (i.e., shortest scaled distances that obtain edges of neighboring surface nodes and their interconnections) and the results obtained used to model effects of surface diffusion with nonlinear reactions. Further analysis of evolved spatiotemporal patterns may be carried out by IGMDS because high-dimensional snapshot data can be efficiently projected to a transformed subspace with reduced dimensions. Validation of the IGMDS methodology is carried out by comparing results with reduction capabilities of conventional principal component analysis for simple situations of reaction and diffusion on surfaces. The usefulness of the IGMDS methodology is shown for analysis of complex patterns formed on both regular and fractal surfaces, and using generic nonlinear reaction-diffusion systems following FitzHugh Nagumo and cubic reaction kinetics. The studies of these systems with nonlinear kinetics and noise show that effects of surface disorder due to fractality can become very relevant. The relevance is shown by studying properties of dynamical invariants in IGMDS component space, viz., the Lyapunov exponents and the KS entropy for interesting situations of spiral formation and turbulent patterns.     

A review on thiocyanate methods for the estimation of molybdenum by molecular absorption spectroscopy

A review is presented on thiocyanate methods for the estimation of molybdenum in a wide variety of samples. They include conventional thiocyanate methods in which molybdenum forms an orange red complex with the thiocyanate ions and improved thiocyanate methods where the sensitivity is increased through the formation of ternary ion association complex.     

Determination of enzyme kinetic parameters of cyclic CMP-specific phosphodiesterase by quantitative fast atom bombardment tandem mass spectrometry

The determination of cytidine 3′,5′-cyclic monophosphate-specific phosphodiesterase activity by means of fast-atom bombardment (FAB) mass Spectrometry with mass-analysed ion kinetic energy (MIKE) spectrum scanning is described. Initial efforts to determine the activity of the enzyme by this method were unsuccessful owing to the obfuscation of sample-related peaks by peaks emanating from the incubation buffer and cation adducts; dilution of buffer and a desalting procedure overcame these difficulties. In the resulting positive-ion FAB mass spectra, characteristic peaks of the enzyme substrate and product could be readily identified and the protonated molecular ions selected for MIKE scanning. By spiking enzyme incubates with known amounts of substrate and product, and measuring peak heights in the MIKE spectra of both spiked and unspiked samples, the substrate/product ratio at the end of a series of phosphodiesterase incubations was determined. From the data obtained, the K_m and V_max of the phosphodiesterase were calculated as 6.08 mM and 11 μmol min^?1 mg^?1, respectively, showing good agreement with the analogous values of 8.06 mM and 5.8 μmol^?1 min^?1 mg^?1 obtained by radioactive assay.     

Electrocatalytic treatment of waste: studies on discoloration of an industrial azo dye effluent

A textile dye effluent containing chiefly reactive azo dyes has been treated electrochemically for discoloration and COD (chemical oxygen demand) reduction at different current densities, flow rates and dilution. Experiments have been carried out in a thin electrochemical reactor under single pass conditions using a dimensionally stable catalytic anode (DSA) and a stainless steel cathode.     

Performance of immobilized Saccharomyces cerevisiae in the removal of long lived radionuclides from aqueous nitrate solutions

The efficiency of tailor made immobilized Saccharomyces cerevisiae(biomatrix) for the sorption of radionuclides ²³³U, ²³⁹Pu, ²⁴¹Am, ¹³⁷Ce, ¹⁴⁴Cs, ^103,106Ru and ⁹⁰Sr from aqueous nitrate solutions at different pH was studied. Effect of ionic strength, anionic components, initial metal concentration and particle size of the biomatrix on the sorption of metal ions were investigated. At pH in the range of 1 to 2 more than 95% sorption of U, Pu, Am and Ce could be accomplished, while that of Ru was 65%. Sorption of Cs and Sr were negligible under similar conditions. The metal ion-biomatrix system for Pu, Am and Ce reached equilibrium within 60 minutes. In the case of U, equilibrium attained in 100 minutes. The presence of anionic components, Cl^-, C₂O₄ ^2-, CH₃COO^-, NO₃ ^- and SO₄ ^2- (up to 0.5 mol^.dm^-3 of their individual concentration) in the aqueous solutions has no effect on the sorption of Pu by the biomatrix. Sorption of U, Pu, Am were observed in the presence of several cationic impurities such as Al, Be, Cd, Cr, Fe, Mn, Pb, Ce, Dy, Eu, Gd and Sm. Metal sorbed on the biomatrix could be leached out using 5 mol^.dm^-3 nitric acid. The I.R spectra of U bearing biomatrix suggest chemical interaction of uranyl ion with the biomatrix.     

Relative reactivities of glycerophosphates towards permanganate in perchloric acid medium

Summary The reactivities of - and -glycerophosphates towards MnO ₄ ^– in HClO₄ medium have been examined. The reactions between glycerophosphates and MnO ₄ ^– are first order with respect to [glycerophosphate], [MnO ₄ ^– ] and [H⁺]. There is no evidence for cleavage of the C–O–P bond rather than the terminal –CH₂OH group being oxidized to the respective phosphoglyceraldehyde.