Dielectric permeability of silicate enamels

Translated from Steklo i Keramika, No. 2, pp. 19–20, February, 1988.     

Formic Acid Production Via Methane Peroxide Oxidation Over Oxalic Acid Activated Fe-MFI Catalysts

Topics in Catalysis - The process of synthesis of formic acid via partial peroxide oxidation of methane over Fe-MFI zeolites, as well as the influence of the catalyst activation by oxalic acid on...     

Environmentally friendly,energy-saving technology for encapsulation of granules in thin waterproof polymer shells

For enhancing environmental safety, aqueous emulsions of polymer solutions are suggested as encapsulants for the combined process of prilling of melt drops in an encapsulant solution followed by separation of the encapsulant solvent from the granules by utilizing the residual heat of the phase transition.     

Microbial levan biopolymer production and its use for the synthesis of an antibacterial iron(II,III) oxide–levan nanocomposite

Levan biopolymer is an exopolysaccharide characterized with biocompatibility and unique properties that is widely used in different industries. In this study, this biopolymer was used to synthesize a nanocomposite containing magnetic nanoparticles of iron with antibacterial effects. The effects of three factors at three levels of sucrose (5, 7, and 9 g), KH₂PO₄ (0.3, 0.5, and 0.7 g), and soy flour (3, 5, and 7 g) were evaluated to produce levan exopolysaccharide by Bacillus polymyxa PTCC1020. Nine experiments were designed with different environmental conditions via the Taguchi method. The nanoparticles of iron oxide were synthesized with the coprecipitation method. In addition, nanocomposites containing magnetic nanoparticles of iron and levan biopolymer were produced. The highest level of levan extraction was observed with conditions of 5 g of soy flour (second level), 0.7 g of KH₂PO₄ (third level), and 5 g of sucrose (first level) as 27 g/L. The Fourier transform infrared analysis and ultraviolet–visible spectroscopy showed the formation of nanocomposites containing magnetic particles of iron. The results indicate that the synthesized nanocomposites had antibacterial effects on both Escherichia coli and Staphylococcus aureus. We concluded that levan and Fe₃O₄ could be used to synthesize antibacterial nanocomposites with high potential for various industrial applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44613.     

Application of Volterra-Wiener spline series for the analysis of nonlinear electric circuits

The functional atlas of the initial system of nonlinear differential equations is split into local charts with the help of a multidimensional Taylor series expansion. In each chart, the approximation with a weakly nonlinear Volterra-Wiener series up to the fourth order is used, where a chart is changed when its boundaries are crossed. It is established that the obtained approach allows one to increase the accuracy and reliability of the calculated output response of the nonlinear system as compared to the classical Volterra-Wiener series approach. The results of the numerical simulation of a nonlinear RC circuit are presented and the efficiency of the proposed method is shown.     

Hydrothermal Solubilization–Hydrolysis–Dehydration of Cellulose to Glucose and 5-Hydroxymethylfurfural Over Solid Acid Carbon Catalysts

Solid acid catalysts based on graphite-like mesoporous carbon material Sibunit were developed for the one-pot solubilization–hydrolysis–dehydration of cellulose into glucose and 5-hydroxymethylfurfural (5-HMF). The catalysts were produced by treating Sibunit surface with three different procedures to form acidic and sulfo groups on the catalyst surface. The techniques used were: (1) sulfonation by H₂SO₄ at 80–250 °C, (2) oxidation by wet air or 32 v/v% solution of HNO₃, and (3) oxidation-sulfonation what meant additional sulfonating all the oxidized carbons at 200 °C. All the catalysts were characterized by low-temperature N₂ adsorption, titration with NaOH, TEM, XPS. Sulfonation of Sibunit was shown to be accompanied by surface oxidation (formation of acidic groups) and the high amount of acidic groups prevented additional sulfonation of the surface. All the Sibunit treatment methods increased the surface acidity in 3–15 times up to 0.14–0.62 mmol g^?1 compared to pure carbon (0.042 mmol g^?1). The catalysts were tested in the depolymerization of mechanically activated microcrystalline cellulose at 180 °C in pure water. The main products 5-HMF and glucose were produced with the yields in the range of 8–22 wt% and 12–46 wt%, respectively. The maximal yield were achieved over Sibunit sulfonated at 200 °C. An essential difference in the composition of main products obtained with solid acid Sibunit carbon catalysts (glucose, 5-HMF) and soluble in water H₂SO₄ catalysts (formic and levulinic acids) as well as strong dependence of the reaction kinetics on the morphology of carbon catalysts argue for heterogenious mechanism of cellulose depolymerization over Sibunit.