On the uniform (C, 1)-summability of Fourier series and integrability of series with respect to multiplicative orthonormal systems

H (G), f(g)H (G) , (, 1)- OHMC G. , OHMC, A. H. . , . , OHMC, lim supp _n=, , ,n .. . , 117 234 . . -      

A Safe Way of Performing Some Dangerous Experiments. II. Construction of a Safety Dropper

Due to the high safety risks, chemistry instructors avoid demonstrating many remarkable experiments based on the addition of a liquid to a solid. Well-known examples of such demonstrations are various pyrotechnic mixtures of potassium chlorate and sugar (sucrose), which are usually activated with a drop of concentrated sulfuric acid. Other attractive demonstrations are the addition of water to freshly prepared magnesium phosphide and addition of water to burning magnesium. In all of these demonstrations the reaction that takes place immediately is very vigorous and can be hazardous for the instructor. Because chemistry teachers and instructors usually try to avoid performing experiments that include a hazard, a number of highly attractive experiments may remain unknown to the public. Using a simple homemade device called a safety dropper, one can perform all of these experiments with complete safety, both for the audience and the demonstrator. Details for performing some of these experiments as well as for the construction of the safety dropper are given in this paper. Video clips of demonstrations are included as an aid for inexperienced instructors.     

Comparative thermal analysis of commercial and low-grade bauxites

This paper presents qualitative and quantitative comparative results on the simultaneous TG-DTG DTA of five commercial and low-grade bauxites. The methodology of qualitative determination of the basic mineral forms contained in bauxites is currently being established. The weight losses relating to the steps in the TG curve allow determination of the contents of the basic minerals in bauxite. These are recalculated as percentages of Al₂O₃, SiO₂, CaO moisture and total volatiles. The final results are in accordance with the results of classical chemical analyses, and this jusitifies the use of this technique as a quick method for qualitative and quantitative determinations of both commercial and low-grade bauxites.

---

Zusammenfassung Qualitative und quantitative Ergebnisse vergleichender simultaner TG-DTG-DTA-Untersuchungen an 5 kommerziellen und geringwertigen Bauxiten werden vorgestellt. Die Methodologie der qualitativen Bestimmung der wichtigsten im Bauxit enthaltenen Minerale wird ausgearbeitet. Die Gewichtsverluste bei den entsprechenden TG-Stufen erlauben die Berechnung der Gehalte an den wichtigsten Mineralen. Diese werden umgerechnet in die Anteile an Al₂O₃, SiO⁰², CaO, Feuchtigkeit und Glühverlust. Letztere Resultate stimmen mit denen klassisch-chemischer Analyse überein. Das erlaubt die Anwendung thermoanalytischer Methoden als Schnellverfahren für qualitative und quantitative Bestimmungen in kommerziellen und geringwertigen Bauxiten.

---

, . , . , , , . , , .

     

Calcium-strontium separation by means of mixed solvent anion exchange

The separation of strontium and yttrium from calcium on the anion exchanger column with alcohol solution of nitric acid as eluent may be described by Glueckauf's model of elution chromatography. Experimental and theoretical results have shown that this separation is characterized by a small number of theoretical plates of the separation column. This model may also be applied for the simulation of the separation of strontium and yttrium from calcium in the strontium isolation from natural samples. The model parameters may be used for the assessment of the optimum column dimension and the optimum working conditions for the isolation of radioactive strontium and yttrium from natural samples.     

Thermal characterization and isothermal kinetic analysis of commercial Creosote decomposition process

Isothermal decomposition process of commercial Creosote was analyzed by thermogravimetric technique in a nitrogen atmosphere, at four different operating temperatures (T = 230, 250, 270, and 290 °C). It was found that the two-parameter autocatalytic ?esták–Berggren kinetic model best describes the investigated process. It was established that the applied logistic function can successfully perform a given kinetic predictions of investigated process, at all operating temperatures. The experimental density distribution function of the apparent activation energy values was evaluated. Based of the characteristic shape of distribution curve, it was concluded that the isothermal pyrolysis of commercial Creosote represent a complex process, which probably includes primary and secondary (autocatalytic) pyrolysis reactions, together with various decomposition reactions and radicals recombination pathways.     

Electrochemical Oxidation of Donepezil and Its Voltammetric Determination at Gold Electrode

The oxidative ability of donepezil, a frequently prescribed drug for the treatment of Alzheimer’s disease is reported for the first time at a gold electrode. It was oxidized by cyclic voltammetry and determined by square wave voltammetry in phosphate buffer electrolyte. Electrochemical degradation of donepezil was carried out by long term potential cycling. The identification and characterization of the major product, isolated by preparative high performance liquid chromatography, was performed by high resolution mass spectrometry and 1D and 2D nuclear magnetic resonance spectroscopy. Donepezil hydroxy derivative was identified as the major electrochemical oxidation product from donepezil.     

Elucidation of the character of radionuclide concentration changes in the near ground layer of air

The Fokker Planck equation was used to analyze the probability of the appearance of radionuclide impulses of any type. Distribution functions for the stationary state and conditions when different factors influence the impulse amplitude and duration are presented. A high degree of correlation was obtained between our results and an analysis of distribution functions of radioactivity and seismic noises in certain regions in Europe and Japan found in the literature. This presents a contribution to the further explanation of the mechanism of radioactivity changes in the near ground layers of air.     

Transition Metal Complexes with Pyrazole-based Ligands. Part 12. Characterisation and thermal decomposition of CuCl2 complexes with di- and trisubstituted pyrazoles

The synthesis of copper(II) chloride complexes with 3,5-dimethylpyrazole, 1-carboxamidine-3,5-dimethylpyrazole, 5-amino-4-carboxamide-1-phenylpyrazole and 4-acetyl-3-amino-5-methylpyrazole is described. The compounds are characterized by elemental analysis, FT-IR spectroscopy, thermal methods, magnetic moment and molar conductivity measurements. Thermal decomposition of the dichloro-(3,5-dimethylpyrazole)-copper(II) complex results in an unstable intermediate with a stochiometric composition. The decomposition of the other compounds is continuous. This revised version was published online in August 2006 with corrections to the Cover Date.