Electrochemical study of redox properties of 2,3,4,5-tetraphenyl-1-heterocyclopenta-2,4-dienes Ph4C4ER1R2 (E = Si,Ge, Sn). A new method for generation of tetraphenylgermole dianion

The electrochemical behavior of the sila-, germa-, and stannacyclopentadienes (metalloles) was studied by cyclic voltammetry. The oxidation and reduction mechanisms of these heterocyclic compounds were investigated. A new method for generation of tetraphenylgermole dianion involving the electrochemical reduction of the corresponding dichlorogermole is proposed. Electrochemical oxidation of the metallole dianions was first studied taking tetraphenylgermole dianion as an example.     

The influence of thermal screens on the temperature distribution,thermal stress,and defect structure during growth of shaped sapphire crystals

The ways in which a block structure is formed in shaped sapphire single crystals grown from melt by the Stepanov method are considered. The measured temperature distributions and results of a mathematical modeling of the heat exchange in the growth zones, as well as the calculated thermoelastic fields and measured residual stresses, are reported. The possibility of effectively controlling the thermal fields and growth of block-free crystals by choosing optimal screening is shown for single crystals in the form of tubes and basal-plane-faceted ribbons.     

Asymptotically Exact Inversion of Uncertain Dynamical Systems

An efficient robust inversion algorithm is proposed, which generates asymptotic estimates of the input signal from noisy output observations with uncertainty in the system parameters. Translated from Prikladnaya Matematika i Informatika, No. 3, pp. 20–32, 1999.     

Magnetization switching in single-domain particles and a response to a field pulse

An equation in the Gilbert form that describes the motion of the magnetization vector in intense high-frequency magnetic fields is solved numerically. The solution obtained is used to study switching of the magnetization of a single-domain ferromagnetic particle that has the shape of an ellipsoid of revolution and possesses cubic anisotropy from the position parallel to an easy axis to the position normal to this axis. The ranges of amplitudes and frequencies of the magnetic field where magnetization switching is observed are determined. An expression for the response of an ensemble of variously oriented particles is derived. It is shown that a particle ensemble generated by an rf field may serve as a data carrier on which information is written and read out by means of nonlinear and linear ferromagnetic resonances.     

Penetration of electromagnetic field through the La-Er-Ba manganite far above the magnetic phase transition temperature

Using the technique of penetration of electromagnetic waves through the bulk samples of La_0.60Er_0.07Ba_0.33MnO₃ manganite, it is shown that in this class of strongly correlated materials the local dynamic magnetic ordering is preserved at the temperature by 66 K above the Curie temperature where the static long-range magnetic order is absent. In this temperature range the dynamic magnetic permeability exceeds unity and is frequency dependent. The average lifetime of local ordered states is estimated.     

Reflection of light from La0.67Ba0.33MnO3

The reflection spectra of La_0.67Ba_0.33MnO₃ ceramic samples prepared with different annealing times in oxygen are investigated. It is shown that conduction is implemented both by low-mobility carriers (polarons) and by comparatively mobile band-type carriers. Fiz. Tverd. Tela (St. Petersburg) 39, 1616–1617 (September 1997)     

Invertibility of systems with unstable zero dynamics

We consider the problem of robust inversion of an uncertain dynamical system with unstable zero dynamics. The solution of the problem is reduced to estimating in real time the bounded solution of an unstable linear differential equation. Estimation algorithms are proposed for one- and two-output systems. Convergence of the inversion algorithms is assessed and the effect of observation errors on the algorithms, i.e., their robustness, is investigated.Translated from Nelineinaya Dinamika i Upravlenie, No. 2, pp. 33–40, 2002.     

On the possibility of distributed associative writing of information by the superimposition of images (plurography)

An expository account is given for the principle of distributed associative writing of optical images by recording in a photosensitive medium the total signal from a set of superimposed images with a random spatial shift. The method preserves the basic characteristic qualities of the holographic method but does not require the use of sources of coherent or monochromatic radiation. The results of an experimental test of the method are presented. Zh. Tekh. Fiz. 68, 98–101 (May 1998)     

Traces of a tsunamigenic earthquake in a rotating stratified ocean

In the framework of the linear long-wave theory, we derive a system of equations that describe the potential and vortex residual hydrodynamic fields that arise in a rotating stratified (two-layer) ocean during tsunami generation by coseismic deformations of the ocean bottom. For the model case of a cylindrically symmetric ocean bottom deformation, we find an approximate analytical solution of the problem. Based on this solution, we analyze the specific features of residual fields due to the presence of stratification for conditions that are typical of real tsunami sources.     

Effect of synthesis on the magnetostrictive properties of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> spinel ferrite

The correlation between methods of synthesis and magnetostrictive properties of ferrite materials is investigated. CoFe₂O₄ spinel ferrite was synthesized using three techniques: solid-phase reactions, thermal hydrolysis, and sol-gel. The effect of the method of synthesis on the magnetostrictive properties of spinel ferrite is demonstrated.