Corrigendum and addendum to my paper concerning Kummer extensions with few roots of unity

This note presents corrections and additions to my paper (J. Number Theory 41 (1992) 322-358).     

Thermal behaviour of CuS (covellite) obtained from copper–thiosulfate system

Thermal behaviour of CuS (covellite) obtained from the Cu(CH₃COO)₂·H₂O and Na₂S₂O₃·5H₂O system, working at different molar ratio (1:6 and 1:4) in presence/absence of NH₄VO₃, was studied. It was established that the presence of vanadium in the system induces a densification of CuS nodules, but do not change the hexagonal CuS structure. It has an important influence in thermal behaviour of copper sulfide CuS obtained also. The morphological characteristics of CuS play an important role in the thermal stability and the stoichiometry of the thermal decompositions. Also, the possibility to obtain copper sulfides with greater cooper content was investigated.     

On the influence of setup parameters on the control of solidification in metal casting

The optimal control of metal solidification in a mold of complex geometry is studied. The underlying mathematical model is based on a three-dimensional two-phase initial-boundary value problem of the Stefan type. The influence exerted on the solidification process and its optimal control by the furnace temperature and the maximum depth to which the mold is immersed in the coolant is examined. The research results are described and analyzed. Some of the results are illustrated.     

Bioanalysis of pentoxifylline and related metabolites in plasma samples through LC‐MS/MS

Analytical aspects related to the assay of pentoxifylline (PTX), lisofylline (M1) and carboxypropyl dimethylxanthine (M5) metabolites are discussed through comparison of two alternative analytical methods based on liquid chromatography separation and atmospheric pressure electrospray ionization tandem mass spectrometry detection. One method is based on a ‘pure’ reversed‐phase liquid chromatography mechanism, while the second one uses the additional polar interactions with embedded amide spacers linking octadecyl moieties to the silicagel surface (C‐18 Aqua stationary phase). In both cases, elution is isocratic. Both methods are equally selective and allows separation of unknowns (four species associated to PTX, two species associated to M1) detected through specific mass transitions of the parent compounds and owning respective structural confirmation. Plasma concentration–time patterns of these compounds follow typical metabolic profiles. It has been advanced that in‐vivo formation of conjugates of PTX and M1 is possible, such compounds being cleaved back to the parent ones within the ion source. The first method was associated with a sample preparation procedure based on plasma protein precipitation by strong organic acid addition. The second method used protein precipitation by addition of a water miscible organic solvent. Both analytical methods were fully validated and used to assess bioequivalence between a prolonged release generic formulation and the reference product, under multidose and single dose approaches. Copyright © 2009 John Wiley & Sons, Ltd.     

Field Theoretic Cogalois Theory via Abstract Cogalois Theory

Abstract Cogalois Theory for arbitrary profinite groups was initiated by T. Albu and ?.A. Basarab [An Abstract Cogalois Theory for profinite groups, J. Pure. Appl. Algebra 200 (2005) 227-250]. The aim of this paper is twofold: firstly, to present the abstract group theoretic versions of various types of Kummer field extensions, and secondly, to show how some basic results of the (Field Theoretic) Cogalois Theory can be very easily deduced from their abstract versions.     

Mathematical modeling and study of the process of solidification in metal casting

The process of melting and solidification in metal casting is considered. The process is modeled by a three-dimensional two-phase initial-boundary value problem of the Stefan type. The mathematical formulation of the problem and its finite-difference approximation are given. A numerical algorithm is presented for solving the direct problem. The results are described and analyzed in detail. Primary attention is given to the evolution of the solidification front and to how it is affected by the parameters of the problem. Some of the results are illustrated by plots.     

Identification of the Thermal Conductivity Coefficient Using a Given Surface Heat Flux

Computational Mathematics and Mathematical Physics - The inverse problem of determining a temperature-dependent thermal conductivity coefficient is studied. The study is based on the Dirichlet...