Synthesis of fluorinated 2-oxo-1,4,2-oxazaphosphol-4-ines and their opening by alcohols

Trifluoromethyl-substituted 1,4,2λ⁵-oxazaphosphol-4-ines from phosphorus dichlorides and N-acylimines of hexafluoroacetone have been synthesized and characterized by ¹H, ¹⁹F, and ³¹P NMR. Alcohols open these oxazaphospholines at the P–O bond, forming the corresponding esters.     

Giant red shift of the absorption spectra due to nonstoichiometry in GdCoO<Subscript>3–δ</Subscript>

The GdCoO_3–δ perovskite is a semiconductor with the energy gap E _g ≈ 0.5 eV from electrical transport measurements. It reveals unusual optical absorption spectra without transparency window expected for semiconductors. Instead we have measured the narrow transmittance peak at the photon energy ε₀ = 0.087 eV. To reconcile the transport and optical data we have studied the effect of oxygen vacancies on the electronic structure of the GdCoO_3–δ. We have found that oxygen vacancies result in the in-gap states inside the charge-transfer energy gap of the GdCoO₃. It is a multielectron effect due to strong electron correlations forming the electronic structure of the GdCoO_3–δ. These in-gap states decrease the transparency window and result in a narrow absorption minimum. The predicted temperature dependence of the absorption spectra has been confirmed by our measurements.     

Measurement of interference-pattern parameters of the near acoustic field of a deep-sea noise source

We present the results of a study of the space-frequency energy distribution of the near acoustic field of noise radiation from a moving source. Dynamic spectrograms of the received signal of noise radiation in the frequency range of 0–2.0 kHz at distances of up to 1300 m are given. It is shown that the variation in the levels of spectral components of the signal due to interference modulation in the near field can attain 12 dB. The interference pattern is shown to occur over the entire range of considered distances of 100–1300m. Within the framework of ray theory, using hydrological data for C(z) in the region of measurements, we calculate the near field for a lumped noise source. The calculation results are in good agreement with the results of field experiments. It is shown that the sound velocity profile C(z) in the region of measurements has a pronounced influence on the interference pattern of the near field. Allowance for C(z) in the calculations of the near acoustic field within the framework of the existing theory allows one to predict the interference pattern and choose optimal distances for measurements under near-field conditions.Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 8, pp. 817–831, August, 1995.     

Heat transfer in a thin layer of a viscous heavy noncompressible liquid under wavy flow conditions

The article describes a method for calculating the flow of heat through a wavy boundary separating a layer of liquid from a layer of gas, under the assumption that the viscosity and heat-transfer coefficients are constant, and that a constant temperature of the fixed wall and a constant temperature of the gas flow are given. A study is made of the equations of motion and thermal conductivity (without taking the dissipation energy into account) in the approximations of the theory of the boundary layer; the left-hand sides of these equations are replaced by their averaged values over the layer. These equations, after linearization, are used to determine the velocity and temperature distributions. The qualitative aspect of heat transfer in a thin layer of viscous liquid, under regular-wavy flow conditions, is examined. Particular attention is paid to the effect of the surface tension coefficient on the flow of heat through the interface.Notation x, y coordinates of a liquid particle - t time - v and u coordinates of the velocity vector of the liquid - p pressure in the liquid - c_v, , T,, andv heat capacity, thermal conductivity coefficient, temperature, density, and viscosity of the liquid, respectively - g acceleration due to gravity - surface-tension coefficient - c phase velocity of the waves at the interface - T_w wall temperature - h₀ thickness of the liquid layer - u₀ velocity of the liquid over the layer Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 147–151, July–August, 1970.     

Fluctuations of the Multiplicity of Co3+ Ions and Softening of the Phonon Spectrum of Rare-Earth Cobalt Oxides

JETP Letters - An unconventional temperature dependence of infrared absorption spectra of rare-earth cobalt oxides LaCoO3 and GdCoO3 has been studied experimentally and theoretically in the...     

Specific features of spontaneous reorientation of the magnetic moment in a single-crystal thin plate of the iron garnet Tb0.2Y2.8Fe5O12

The Faraday effect, light scattering, and changes in the domain structure of a single-crystal thin plate of the iron garnet Tb_0.2Y_2.8Fe₅O₁₂ cut parallel to the (110) crystallographic plane have been experimentally investigated in the temperature range of the spontaneous magnetic orientational phase transition. It has been established that the transformation of the domain structure of the studied sample due to the orientational phase transition is accompanied by a significant temperature hysteresis. A model of the spontaneous reorientation of the magnetic moment vector of the crystal has been proposed by analyzing the results of visual observations of the domain structure and the temperature dependences of the Faraday effect and light scattering. In the proposed model, preference is given to the spin wave mechanism of nucleation of domains of the equilibrium magnetic phases.     

Modeling of the γ → α transformation in steels

A mathematical physically based model of the decomposition of undercooled austenite (γ-phase) with the formation of ferrite (α-phase) and pearlite has been developed. The model differs from the currently existing analogs by a new approach to the inclusion of the effect of complex alloying of steels on the nucleation rate of ferrite grains and on the mobility of the α/γ-phase boundary. In the model, the effect of alloying of steels with substitutional elements on the diffusion coefficient of carbon in the bulk of austenite is taken into account. The results of the modeling of the kinetics of austenite decomposition and the calculation of the final ferrite grain size are in good quantitative agreement with the experimental data obtained for a set of steels with a wide range of chemical compositions.     

Transformation of the domain structure of a cubic ferrimagnetic material at spontaneous spin flip of the easy magnetization axis

The magnetooptical method is used to investigate transformation of the domain structure of a cubic Tb_0.2Y_2.8Fe₅O₁₂ ferrimagnetic material at the temperature of spontaneous spin flip phase transition (SFPF). It is demonstrated that the SFPF is observed in a certain temperature interval in which low- and high-temperature magnetic phase domains coexist. It is established that the character of evolution of the domain configuration in the temperature interval of the spin flip depends significantly on the mechanical stresses presented in the crystal. Experimental results are interpreted in the context of the existing SFPF theory for the cubic crystal.