Research of photocatalytic activity of the Ag/TiO2 catalysts in the reduction reaction of nitrate-ions in aqueous media

We have conducted a research of photocatalytic denitrification of water using modified titanium dioxide obtained by the sol-gel method. We demonstrated the possibility of photoprecipitation of silver particles under the effect of visual light. The use of formic acid as a donor of electrons makes it possible to substantially intensify the process and reduce the yield of a by-product—NH₄ ⁺. It was shown that in the presence of catalysts Ag/TiO₂ and irradiation time for 30 min is achieved a 96% conversion of nitrate ions.     

Data transmission over GSM voice channel using digital modulation technique based on autoregressive modeling of speech production

This paper presents a novel digital data modulation and demodulation algorithm ARDMA based on the principles of autoregressive modeling (AR) of speech production. In the first step a sustained voiced speech signal characteristics are analyzed using autoregressive modeling principle and then the two sets of linear prediction (LPC) coefficients are obtained and converted to linear spectrum frequencies (LSF). The input binary data stream drives the selection mechanism of LSF coefficients which are then applied as filter coefficients of the modulation signal synthesis filter. This filter is excited with specially designed excitation signal which corresponds to the basic characteristics of typical excitation signal of human vocal tract. Finally, a speech-alike modulation signal is produced. This modulation signal is then sent through the voice channel of the GSM system. The demodulator analyzes the incoming modulation signal using autoregressive modeling. The most likely LSF vector which modulated the particular symbol was determined by the demodulation process and converted to the respective string of binary data. The performance of proposed modulation scheme was compared to the regular frequency shift keying method (FSK). The performance improvement of ARDMA against FSK is observed at higher bit-rates in the case of three compared GSM speech coders.     

Electric conduction of ceramic membranes modified with nanoparticles of an inorganic ion exchanger

The article has investigated electric conduction of systems including composite ceramic membranes whose macropores are filled with an ion-exchange component—hydrated with zirconium dioxide and the solution of 1,1-charged electrolyte HCl. It was found that experimental values of electric conduction of membranes are the values of the same order as the electric conduction of an equilibrium solution. Based on potentiometric transport numbers of counterions we computed electric conduction of the ion-exchanger-solution system with the account of not only electrolyte, which is in intraporous solution, but also of counterions localized in the phase of the ion-exchanger. We have proposed a model equation linking electrical conduction of the membrane, the ion-exchanger, and the solution. An assumption was made about the presence in the pores of nano-dimensional channels being formed when introducing the ion-exchanger to the matrix.     

PHYSIOLOGICAL TESTING OF CARBON NANOTUBES: ARE THEY ASBESTOS-LIKE?

To determine whether carbon nanotubes can induce any significant health hazards we applied methods routinely used in the pathophysiological testing of asbestos-induced disease to show that the soot with a high content of CNTs does not induce any abnormalities of pulmonary function or measurable inflammation in guinea pigs treated with carbon nanotubes.     

Formation of zinc oxide nanoparticles during electric discharge in water

A method for obtaining nanodimensional structures of zinc oxide (ZnO) by means of electric discharge in water is described. Data on the phase composition and luminescent properties of the synthesized ZnO powder deposited from a colloidal solution onto single crystal silicon surface are presented. It is shown that the partial concentrations of zinc in the oxide and metallic phases in the colloidal solution depend on the supply of oxygen to the zone of the chemical reaction. Optimum conditions for the discharge synthesis of nanodimensional powder with an almost 100% ZnO content have been found.     

Study of the compatibility of phenyltrinitroxylenethane (Phenylxylilethane) with structural materials

The influence of structural materials on the basic electrophysical characteristics (relative permittivity, loss tangent, volume electric resistivity, and electric strength) of phenylxylilethane is considered in this paper.     

Adsorption properties of alumina-aluminum cermets prepared in the aluminum powder reaction with water in the presence of surfactants

By a method of low-temperature nitrogen adsorption-desorption at the gas/solid interface, the trends in the adsorption and capillary-condensation properties of Al₂O₃/Al composites are studied as a function of the way of conjugate stages, namely, the metal hydrothermal oxidation and the replication of colloidal aluminum hydroxide by surfactants of the anionic, cationic, and non-ionogenic types. Original Russian Text ? T.F. Kuznetsova, A.I. Rat’ko, V.E. Romanenkov, S.F. Tikhonov, V.A. Sadykov, 2008, published in Fizikokhimiya Poverkhnosti i Zashchita Materialov, 2008, Vol. 44, No. 4, pp. 410–414.     

Structure and properties of the crystalline-silicon-dioxide-based macroporous ceramics

Samples of macroporous ceramics based on crystalline silicon dioxide-(the pore diameter > 50 μm) with superficial membrane layers (the pore diameter 10–20 μm) are obtained. They meet the demands to porous materials for filtering. The samples based on the polydisperse powder of crystalline silicon dioxide with granulometric composition 100–315 μm, containing 11 wt % of silica-alumina binder, were formed under a pressure of 30 MPa; they demonstrated an optimal combination of porosity and mechanical strength. After thermal treatment the samples’ porosity came to ≈30%; the ultimate stress (compression) limit, to ≈35 MPa. It is shown that multilayer elements for filtering, with membrane layers formed of the silicon dioxide powder suspension, provide the water purification from iron impurity (from 1–2 mg/l and down to 0.3 mg/l, a sanitary standard). The elements for filtering with doubly deposited crystalline silica-based membrane layer (the particle size 10–50 μm) showed optimal combination of operation characteristics and the purity of water from iron. Original Russian Text ? A.I. Ratíko, A.I. Ivanets, T.A. Azarova, S.M. Azarov, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 217–222.     

Effect of a magnetic field on the reverse and forward martensitic transformations in the Fe-33% Ni alloy

Effect of a magnetic field on the reverse and forward martensitic transformation in an iron-nickel alloy with the temperature of the start of the α-γ transformation that is close to the Curie temperature of the γ phase has been studied. The result obtained is explained by the mutual compensation of two mechanisms of the effect of a magnetic field on the reverse martensitic transformation in this alloy. The role played by the magnetic state of austenite in the realization of the corresponding kinetics of the martensitic transformation in the iron-based alloys with a mixed kinetics is discussed.