On complete controllability of linear nonstationary systems

By use of the first integrals of the equations of unperturbed motion we obtain necessary and sufficient conditions for complete controllability of linear nonstationary dynamical systems.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 35, 1992, pp. 160–163.     

States of surface V(IV)-bearing groups in phosphorus-vanadium oxide and titanium-vanadium oxide silica gels made by molecular epitaxy

ESR shows that V(IV) may occur in isolated or interacting vanadium-oxygen groups on the surfaces of catalytically active P-V and Ti-V-bearing silica gels; there is a relationship between the V(IV) content and the phthalic anhydride selectivity in the oxidation of o-xylene.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 3, pp. 277–282, May–June, 1992.     

Symmetry algebra of nonlinear integrable equations

The complete symmetry algebras of the Veselov-Novikov equation and of the modified Kadomtsev-Petviashvili equation are constructed. Some related questions are discussed.P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 95, No. 1, pp. 34–41, April, 1993.     

Radioanalytical monitoring of the formation of barium sulfate in aqueous solutions

The formation of barium sulfate in aqueous media causes problems of insoluble scale formation. On the other hand, the coprecipitation of uranium and transuranium elements with barium sulfate has been suggested for the determination of these elements in environmental monitoring processes. Therefore, the study of barium sulfate crystal growth is required. The investigations done so far suffer from the low sensitivity of the analytical methods used. In the present work we have overcome this problem by using¹³¹Ba for the preparation of supersaturated solutions. Thus kinetics parameters such as induction time and precipitation rates were measured. The polynuclear mechanism was found to be operative at high and the spiral growth at low supersaturations.     

Electrical properties of Si-SiO2 systems after the application of a magnetic field

Weak-signal methods are used to study long-term changes in the electrophysical and photoelectric properties of Si-SiO₂ systems of n- and p-type semiconductors after the action of a steady magnetic field of 10² Oe. It is found that the field electrode can produce regions characterized by the anomalous recombination, migration, and transformation of nonequilibrium charge carriers, leading to a quasi-oscillating change in the recombination activity of the semiconducting system. It is observed that the magnetically induced changes in the system depend on the impurity of composition of the semiconductor. The results obtained are attributed to the decomposition of the growth structures of complexes and subsequent clustering of the decomposition products at elastic stress sinks. Tomsk State Academy of Control Systems and Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 62–66, February, 1997.     

Antimicorbial effects of newly synthesized organotin(IV) and organolead(IV) derivatives

Triorganotin(IV) and triorganolead(IV) derivatives of the types Me₃Sn(SCZ) and Ph₃Pb(SCZ) (where SCZ^? is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper.