Renormalization group approach to lattice gauge field theories

We study four-dimensional pure gauge field theories by the renormalization group approach. The analysis is restricted to small field approximation. In this region we construct a sequence of localized effective actions by cluster expansions in one step renormalization transformations. We construct also -functions and we define a coupling constant renormalization by a recursive system of renormalization group equations.     

The Monte-Carlo model of a light-emitting diode

The first complete Monte-Carlo model of a surface light-emitting diode is presented in this paper. In the model all important phenomena (including the two-dimensional diffusion of minority carriers before their recombination in the active region and the re-emission of radiation) are taken into account. The influence of various construction parameters on the external quantum efficiency of the homojunction GaAs diode is examined.     

On a two-velocity model of the Boltzmann-Enskog equation

Summary A simple two-velocity model (-model)of the Boltzmann-Enskog equation for a gas of hard spheres is proposed. Physical properties of such a model are analyzed and its differences with respect to the Carleman model are investigated. Global existence theorems and some qualitative properties of solutions of the -model are also proved.On leave from Dept. of Mathematics and Mechanics, University of Warsaw, Poland.     

Thermal decomposition of Cd(CH3COO)2·2H2O studied by a coupled TG-DTA-MS method

The thermal decomposition of cadmium acetate dihydrate in helium and in air atmosphere has been investigated by means of a coupled TG-DTA-MS method combined with X-ray diffraction analysis. Dehydration of Cd(CH₃COO)₂·2H₂O is a two-stage process with Cd(CH₃COO)₂·H₂O as intermediate. The way of Cd(CH₃COO)₂ decomposition strongly depends on the surrounding gas atmosphere and the rate of heating. CdO, acetone and CO₂ are the primary products of decomposition in air. In helium decomposition goes by two parallel and consecutive reactions in which intermediates, Cd and CdCO₃, are formed. Metallic cadmium oxidizes and cadmium carbonate decomposes giving CdO. Some of the metallic cadmium, depending on the heating rate and the concentration of oxygen, evaporates. Acetone is partially oxidized in secondary reactions with oxygen. This revised version was published online in July 2006 with corrections to the Cover Date.     

Domain-wall energy in sintered Nd15Fe77B8 permanent magnet

From measurements of the magnetic domain widthsD versus grain thicknessL, we have determined the domain wall energy in the demagnetized state for a sintered Nd₁₅Fe₇₇B₈ magnet: = 56 erg/cm². Using this wall energy and the published magnetocry-stalline constantK ₁=4.9×10⁷ erg/cm³, we have calculated the exchange constantA=4.0×10^–6 erg/cm, domain wall thickness _B=89 Å, and the critical diameter for single domain particlesD _c=0.67 m.     

Synthesis and characterization of metal polycarboxylates constructed from lanthanides(iii) and 1,2,4,5-benzenetetracarboxylic acid

The complexes of yttrium(III) and lanthanides(III) with 1,2,4,5-benzenetetracarboxylic acid were prepared as crystalline solids of the general formula Ln₄(C₁₀H₂O₈)₃⋅14H₂O. They are insoluble in water. On heating in air or inert gas atmosphere all compounds lose water molecules; next anhydrous compounds decompose to oxides. The yttrium complex and heavy lanthanide (from Ho to Lu) ones crystallize in monoclinic crystal system. The dehydration does not change the crystal structure of the compounds.     

Effect of the fibre-forming material structure and silica nanoparticles

The paper discusses the thermal properties of alginate fibres made from alginic acid or sodium alginate and from alginates substituted with divalent metal ions during the fibre-forming stage. Alginate fibres with an addition of silica nanoparticles have also been examined. The selection of fibre-forming parameters was intended to obtain the best either sorption or strength properties depending on the specific fibre application. Thermal curves of the fibres under investigations obtained by under air atmosphere and differential scanning calorimetry (DSC) under neutral gas atmosphere have been interpreted from the view of physical and chemical changes in the fibre-forming material. Based on thermogravimetric curves, the fibre thermal stability indices have been determined. It has been found that the addition of silica nanoparticles exerts a positive influence on the thermal properties of the examined fibres.