An adsorption and calorimetric study of the interaction of hydrogen with chromium oxide

The chemisorption of hydrogen on porous chromium oxide was studied at temperatures up to 723 K under the conditions of controlled oxygen, hydrogen, and water contents in the samples. The molar heats of chemisorption were measured at temperatures up to 473 K. Hydrogen was found to be chemisorbed (310 kJ/mol) in the form of water and absorbed into oxide volume (165 kJ/mol) in the form of coordination bound atoms. Changes in the molar heat of the processes during chemisorption were caused by changes in the ratio between chemisorption and sorption. The phenomena observed and quantitative results could be explained by simple Langmuir concepts without assumptions of surface heterogeneity.     

Total property of bounded approximation

Kharkov. Translated from Sibirskii Matematicheskii Zhurnal, Vol. 30, No. 3, pp. 180–181, May–June, 1989.     

Models of non-gaussian active noises influencing receiving antenna arrays

We study the reasons for the non-Gaussian nature of an active noise field as waves propagate in a homogeneous and a randomly inhomogeneous medium. The statistical properties of a propagating wave are analyzed, which allows us to find multidimensional probability densities in both cases. Antiaircraft High School, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 769–779, June, 1997.     

Q factor of lithium niobate piezoelectric transducers at high excitation levels

The variations of the electroacoustic parameters (Q factor, electromechanical coupling coefficient, and capacitance) of lithium niobate piezoelectric transducers with increasing high-frequency excitation voltage are studied experimentally. The relative acoustic strain is found to reach a maximum of about 10^?4 in the frequency range from 2 to 3 MHz. The Q factor of the transducers may increase by 100% in the range of acoustic strains studied. This increase is accompanied with acoustic emission. The reason for this effect is the block structure of the lithium niobate crystal.     

Pairs of regularizable invertible operators with a nonregularizable superposition

Translated from Teoriya Funktsii, Funktsional'nyi Analiz i Ikh Prilozheniya, No. 52, pp. 78–88, 1989.     

Basic and quasibasic subspaces of adjoint Banach spaces

Translated from Matematicheskie Zametki, Vol. 47, No. 6, pp. 85–90, June, 1990.     

Mass Spectrometric Analysis of Microcystins from Cyanobacterial Biomass: Optimization of the Sample Preparation Procedure

The sample preparation procedure for determination of microcystins from biomass by the LC–MS method was optimized. Treatment of freeze-dried biomass samples with acetonitrile prior to the main extraction was effectively used for decreasing the amount of protein-like matrix compounds in extracts. Use of acetonitrile–water mixtures during the main ultrasound-assisted extraction allowed increasing the total microcystins amount in the resultant extracts compared to the traditional extraction using 75% methanol.     

Molecular dynamics simulation of shock compression of metals: Iron and iron-sulfur solutions

The embedded atom model potential suggested earlier was improved to correctly describe iron at high pressures and temperatures. Correction was introduced using the shock compression data. The properties of body- and face-centered cubic (BCC and FCC) lattices and liquid iron at compression degrees up to 50% of the normal volume and temperatures up to 10000 K were calculated. At degrees of compression 0.7–0.6 and 0 K, the FCC lattice is thermodynamically stable. The temperature of fusion increases to ≈9700 K at compression to 50% of initial volume (pressure 585 GPa). The pressure of pure iron at 5000 K and density 12.5 g/cm³ is ≈250 GPa and is substantially lower than in the center of the Earth according to the geophysical data (360 GPa). An embedded atom model potential for a 10 at % solution of sulfur in iron which allows the properties of the melt in the center of the Earth to be described correctly is suggested; the viscosity of the melt under these conditions is not high (0.0156 Pa s); these results are close to those obtained in ab initio calculations. The possibility of partial Earth core crystallization is shown.