Syntheses and reactions of some fluorinated dienes,cyclobutenes and furans

There are many reports¹ of the pyrolysis of fluorinated organic compounds, including the defluorination of cyclic fluorocarbons over iron to give aromatic compounds. Extending this technique we have investigated the flow pyrolysis of some readily accessible unsaturated fluorocarbons, such as I, II, and III, and found these to be synthetically

useful routes to fluorinated dienes, cyclobutenes, and furans. Pyrolyses were carried out using a nitrogen flow over platinum, iron or caesium fluoride heated at 430–700°. The various products can all be rationalized in terms of intermediate allylic radicals, and the solid substrate influences which allylic radicals are formed.We are also investigating the chemistry of those now accessible compounds, such as IV, V, and VI, and some of the preliminary results are described.

For example the fluoride ion induced dimerisation of IV gave two major products VII and VIII via a particular interesting mechanism.

     

Influence of disorder in crystal structure on ferroelectric phase transitions

A new model of ferroelectric phase transitions in disordered crystals is developed. The model takes into account the nonequivalence of the structural environment of identical ions, which alters the balance of forces governing ferroelectric structural instability. In contrast with its predecessors, the new model can be used for qualitative and, in many cases, quantitative predictions of the temperature range of the diffuse ferroelectric phase transition and the value of the disorder-induced shift of the average transition temperature as a function of the degree of disorder and chemical composition. This conclusion is confirmed by a comparison of the theoretical results with an abundance of known experimental facts. Zh. éksp. Teor. Fiz. 111, 1817–1832 (May 1997)     

Frequency dependence of propagation time and total losses of magnetoelastic waves in single crystals of yttrium-iron-gallium garnets

The possibility of using single crystals of yttrium-iron-gallium garnets (YIGG) as media for the propagation of magnetoelastic waves in the long-wave region of the uhf range is considered. Frequency dependences are obtained for the total losses and the maximum controllable lag for YIGG single crystals with various levels of saturation magnetization. An empirical formula relating the specific damping of magnetoelastic waves with the saturation magnetization and frequency is proposed. The possibility of choosing a YIGG composition optimal for a given frequency in the range 200–2000 MHz is demonstrated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 61–65, March, 1977.     

Co-doping effect on the properties of scandia stabilized ZrO2

The influence of low concentrations (1 mol %) of few co-dopants (Y₂O₃, La₂O₃, CeO₂, Gd₂O₃, Er₂O₃, ZnO) on the structure and characteristic of 10 mol % scandia stabilized zirconia was studied. Sintering kinetics and thermal expansion coefficients of synthesized solid eletrolytes were determined. It was found that co-doping increased the conductivity of electrolytes at temperature below 550°C. However, at high temperatures, the introduction of co-dopants decreased the conductivity; moreover, this reduction was more severe the more the ionic radii of Zr⁴⁺ and co-dopant differ.     

Role of anionic isoforms of peroxidase during phytopathogenic infection of plants from the family Malvaceae

An increase of the activity and the appearance of new isoforms (high-and low-molecular-weight) in the isospectrum of peroxidase were noted after the action of the phytopathogen Verticillium dahliae on plants from the family Malvaceae. The temperature was shown to have an effect on the resistance to infection of the studied plants. Isoelectric focusing showed that anionic isoforms of peroxidase had isopoints 4.7 and 3.5. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 280–283, May–June, 2008.     

Excitation of a tube wave in a borehole by an external isotropic point source

The excitation of a tube wave in an infinite fluid-filled borehole by an external isotropic point source is considered. The solution to the problem is obtained in the form of a double integral with respect to the ray parameter (slowness) and frequency. The integral with respect to the slowness is transformed to a contour integral in the complex slowness plane and then reduced to the integral over the edges of the cut of the vertical slowness function and the semiresidues at the poles. An asymptotic expression for the wave field in the borehole is obtained with allowance for the radiation condition at infinity. It is shown that, when a longitudinal spherical wave is incident on the borehole, only one low-frequency Stoneley wave is excited and not two, as was assumed earlier [1].