Mössbauer study of carbide phases in catalysts for ammonia synthesis

Samples of a catalyst CA-1 for ammonia synthesis were studied. After reduction the samples were treated with CO₂ or with a mixture of 1% O₂+2.4% H₂O+CO₂ at temperatures between 600 and 783 K. Mössbauer spectroscopy data indicate that above 600 K carbide phases and magnetite are formed. A probable mechanism for carbide formation is suggested.     

Crystallisation Mechanism in Gradient Temperature Zone Melting

Theory of zone recrystallization in the framwork of already known models of normal crystal growth, growth by screw dislocations and by two-dimensional nucleation is discussed. By mathematical treatment, different from Tillers approach, analytical expressions for supersaturation at the crystallisation interface, for superheating at the dissolution interface, growth rate and some other parameters have been obtained for both cases of normal and screw dislocations growth. It is possible to determine the growth mechanism.     

Topological interference in nonlinear bounded systems

Topological interference is a self-interference of wave packets evolving in quantum wells. A particular manifestation of this self-interference is an effect with no classical counterpart-a symmetric wave packet splitting. Employing reasonable approximations, we give a semianalytical interpretation of this effect.     

On the problem of oscillatory laminar flow of elastico-viscous liquids in channels

Summary A possibility is shown for an exact solution by means of tabulated functions of the problem about the velocity profile of oscillatory flow of elastico-viscous liquids in channels with annular cross-section.

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Zusammenfassung Es wird gezeigt, wie man mit Hilfe tabulierter Funktionen das Geschwindigkeitsprofil in einem Rohr mit Kreisring-Querschnitt für die oszillierende Strömung einer viskoelastischen Flüssigkeit bestimmen kann.

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Iron-oxide-modified nanosized diamond: preparation, characterization, and catalytic properties in methanol decomposition

Nanosized diamond (UDD), obtained by a detonation procedure, was modified with iron from the corresponding acetylacetonate precursor under various pretreatment conditions. Nitrogen physisorption, X-ray diffraction, temperature-programmed reduction, and FTIR and M?ssbauer spectroscopy were used for their characterization. The samples' catalytic behavior in methanol decomposition was also studied. The physicochemical and catalytic properties of the obtained materials (Fe/UDD) were compared with those of other iron-oxide-modified mesoporous supports with different nature and functionality (MCM-48 silica and CMK-1 carbon). The highest catalytic activity and stability was achieved with air-pretreated Fe/UDD.     

Changes in the anti-inflammatory activity of soy isoflavonoidgenistein versus genistein incorporated in two types of cyclodextrin derivatives

ABSTRACT: BACKGROUND: The isoflavonoid genistein represents the major active compound from soybean, the vegetalproduct from Glycine max (Fabaceae). The aim of this study is to prove that genistein wasincorporated in two semisynthetic cyclodextrins, beta-cyclodextrin derivatives:hydroxypropyl-beta-cyclodextrin and randomly-methylated-beta-cyclodextrin as well as to compare the anti-inflammatory activity of genistein with that of genistein incorporated inthese two types of semisynthetic cyclodextrins. RESULTS: The animal studies were conducted on 8-week old C57BL/6 J female mice. Inflammation wasinduced in both ears of each mouse by topical application of 10 micrograms 12-Otetradecanoylphorbol-3-acetate dissolved in 0.1 ml solvent (acetone : dimethylsulfoxide in amolar ratio 9:1). Thirty minutes later treatment was applied. The inflammatory reaction wascorrelated with increased values in ear thickness. Treatment with genistein and genisteinincorporated in the two cyclodextrins led to decreased values for ear thickness. Better antiinflammatoryaction was found for the complexes of genistein. Both haematoxylin-eosinanalysis and CD45 marker expression are in agreement with these findings. CONCLUSIONS: Results allow concluding that genistein is an active anti-inflammatory phytocompound andits complexation with hydrophilic beta-cyclodextrin derivatives leads to a stronger antiinflammatoryactivity.     

Some Data on the Dynamics of Corrosion Processes in Water Circulation Cooling Systems

 Both origin and changes in phase composition of corrosion products deposited on Standard Carbon Steel during 313 days of exposure were monitored by X-ray diffraction analysis. The corrosion was caused by water from industrial cooling systems in the presence as well as in the absence an inhibitor. The predominant components of the corrosion products were initially found to be carbonates such as CaCO₃ as well as hydroxycarbonates like Fe₂(OH)₂CO₃; they were followed by the appearance of other products such as γ-FeOOH, Fe₃O₄, and α-FeOOH. The corresponding chemical reactions were found to comply with first-order kinetics. The rate constants were calculated from changes in the relative intensities of the corresponding X-ray patterns of Standard Carbon Steel samples. In absence of the inhibitor the rate of the corrosion processes were found to be 2.3 to 3 times higher than in its presence.     

A Mössbauer study of synthetic magnetite

Samples of magnetite, prepared by standard methods for obtaining of melted ammonia synthesis catalysts have been studied. The samples contain small amounts of additives, such as K₂O (0.4–1 mass%), CaO (0.7–1.5 mass%), Al₂O₃ (0–2 mass%), WO₃ (0–1 mass%) and MoO₃ (0–0.6 mass%). Some influences of the additives to magnetite, as well as formation of other individual phases were established.