Production of high yield [13N] ammonia by proton irradiation from pressurized aqueous solutions

The method of direct production of large quantities of [¹³N]ammonia in the cyclotron water target for clinical cardiac studies by PET or synthetic uses was considered. Two main approaches based on the proton irradiation either of dilute aqueous ethanol solution under helium pressure or pure water pressurized by hydrogen were evaluated. Using ethanol as a target additive at the relatively low helium pressure of 400 KPa up to 22.2 GBq (600 mCi, EOB) of final product can be produced with radiochemical purity of more than 98%. Under comparable conditions the water target pressurized by hydrogen was about two times less effective for production of [¹³N]NH₃ because of the formation of considerable amounts of [¹³N]N₂. A possible mechanism of labelled nitrogen production was discussed.     

Discrimination of metamorphic diamond populations by Raman spectroscopy (Kokchetav, Kazakhstan)

Metamorphic diamond is a powerful but frequently debated indicator for ultrahigh-pressure metamorphic (UHPM) conditions. Because of their small size, their optical identification needs confirmation. Characteristics of chemically extracted microdiamonds from Kokchetav, identified by different analytical methods, are used here for unambiguous in situ identification by Raman microspectroscopy. Differences appear in the diamond spectra and the Raman analytical method is explored as a helpful tool in the discrimination between diamond populations from four different UHPM lithologies of Kokchetav. Not considering the graphite-coated diamond, out of the reach of the laser wavelength used here, the comparison of these Kokchetav Raman spectra may provide additional information in other UHPM studies.     

Generalized theorems of Liénard and Shepherd

The paper considers a real polynomial p(x)=₀+₁x+...+_nxⁿ(₀ > 0) for which there hold inequalities ₁>0, ₃>0, ... or ₂>0, ₄>0, ..., where ₁, ₂, ..., _jn are the Hurwitz determinants for polynomial p(x). It is proven that polynomial p(x) can have, in the right half-plane, only real roots, where the quantity of positive roots of polynomial p(x) equals the quantity of changes of sign in the system of coefficients a₀, a₂, ..., a_n–2, a_n, when n is even, and ₀, a₂,..., a_n–1, a_n, when n is odd. From the proven theorem, in particular, there follows the Liénard and Shepherd criterion of stability.Translated from Matematicheskie Zametki, Vol. 22, No. 1, pp. 13–21, July, 1977.     

Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles from Amidoximes and Aldehydes in the Superbasic System NaOH/DMSO

Russian Journal of Organic Chemistry - A new procedure has been proposed for the synthesis of 3,5-disubstituted 1,2,4-oxadiazoles by reaction of amidoximes with aldehydes in the superbasic system...     

Synthesis of sulfonate derivatives of 4-heteryl-isoxazoles

Synthesis procedure of 3,5-dimethyl-4-heteryl-isoxazoles by reaction between heterocyclic aldehydes and nitroethane in the presence of base was developed. Sulfochlorination of the resulting compounds was studied.     

Effect of donor-acceptor sites at a barium titanate surface on the properties of composites based on cyanoethyl polyvinyl alcohol

The changes in the specific surface area and composition of donor-acceptor sites caused by hydration and thermal treatment of dispersed BaTiO₃ were determined. Modified barium titanate was mixed with cyanoethyl polyvinyl alcohol to form composite films with a relative permittivity of up to 180. The relationship between the functional composition of the surface and the particle size of modified barium titanate, on the one hand, and the relative permittivity of the composite film, on the other, was derived within the framework of the thermodynamic model. This relationship makes it possible to predict the effect of modification on the electrophysical properties of polymer composites.     

Convenient synthesis of novel 5‐substituted 3‐methylisoxazole‐4‐sulfonamides

A number of novel sulfonamide derivatives of 5‐substituted‐3‐methylisoxazole were synthesized and characterized, starting from 3,5‐dimethylisoxazole. Key steps include the generation of 3,5‐dimethylisoxazole‐4‐sulfonamides followed by their reactions with N‐(dimethoxymethyl)‐N,N‐dimethylamine or various aromatic and heteroaromatic aldehydes. As a result, a series of novel aryl/heteroaryl‐ and aminovinylsubstituted derivatives of the isoxazole heterocycle were obtained. The scope and limitations of the developed approach are discussed.     

Influence of grain boundaries on resistivity of manganites La1 − x K x MnO3

Results of investigation of resistivity and magnetoresistance of manganites La_{1 − x} K _x MnO₃ (x = 0.050–0.175) are presented. Behavior of resistivity ρ(T) in the paramagnetic and ferromagnetic phases has been described. To describe ρ(T) near the phase-transition temperature, notions of the percolation theory have been used. Two maxima have been found in the dependence ρ(T); their appearance has been attributed to the ceramic nature of the studied samples. The observed increase in magnetoresistance with a decrease in temperature is caused by intergranular spin-polarized tunneling of charge carriers.     

Comparative performance of living and dead bony tissue under static and dynamic loading

The dependence of the mechanical properties of bony tissue on different conditions of storing the samples has been studied. As the performance characteristic under static loading we used the ultimate compressive strength of the bony tissue, and under dynamic loading we used the specific impact strength.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.I. M. Sechenov First Moscow Medical Institute. Translated from Mekhanika Polimerov, No. 4, pp. 647–649, July–August, 1975.     

Synthesis of substituted 5-hydroxypyrazolo[1,5-a]quinoxalin-4-ones

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