SYNTHESIS AND PROPERTIES OF Sr-CONTAINING TRYCALCIUM PHOSPHATE

Sr -замещенный трикальцийфосфат был получен методом осаждения из водных растворов. Синтетические твердые фазы исследовали с помощью рентгеннофазового анализа, ИК-Фурье спектроскопии, сканирующей электронной микроскопии, энергодисперсионного анализа. Надосадочная жидкость была исследована на наличие ионов Ca и PO для вычисления Са/Р соотношения. Выявлено, что ионы стронция входят в состав трикальцийфосфата, однако не изменяют его фазовый состав. Добавление ионов стронция в исходный раствор способствует уменьшению размеров кристаллитов и увеличению их пористости. Данные по энергодисперсионному анализу подтвердили, что ионы стронция входят в состав образцов ТКФ. Но при увеличении их концентрации, полного замещения ионов кальция на ионы стронция в структуре ТКФ не происходит. При изучении биорезорбируемости полученных образцов с помощью прямой потенциометрии установлено, что образцы, содержащие ионы стронция в своем составе, имеют меньшее значение скорости резорбции. При этом, наибольшие значения скорости растворения фиксируются в кислых средах. Sr -substituted tricalcium phosphate was obtained by precipitation from aqueous solutions. Synthetic solid phases were investigated using X-ray phase analysis, IR spectroscopy, scanning electron microscopy, energy dispersive analysis. The supernatant was examined for the presence of Ca and PO4 ions to calculate the Ca/P ratio. It was revealed that strontium ions are part of tricalcium phosphate, but do not change its phase composition. The addition of strontium ions to the initial solution contributes to a decrease in the size of crystallites and an increase in their porosity. When studying the bioresorbability of the obtained samples using direct potentiometry, it was found that the samples containing strontium ions in their composition have a lower value of the rate of resorption. Energy dispersive analysis data confirmed that strontium ions are included in the composition of TCP samples. But with an increase in their concentration, complete replacement of calcium ions with strontium ions in the TCP structure does not occur. At the same time, the highest values of the dissolution rate are recorded in acidic media.

The process of forming welded joints by high-voltage capacitor welding

The article substantiates the relevance of obtaining welded joints from dissimilar alloys with minimizing the processes responsible for the formation of intermetallic joints by using high-voltage capacitor welding with an induction-dynamic drive. A schematic diagram of high-voltage capacitor welding is given, the physical nature of the work is described. The parts to be welded are connected in series to an electric circuit and an inductor, which is a feature of this method. The physical processes and stages of high-voltage capacitor welding with an induction-dynamic drive are described. Comparison and analysis of high-speed photographic recording with oscillograms of current and voltage is carried out. The presence of an inductive resistance in the discharge circuit shifts the discharge current relative to the voltage. Confirmation of the hypothesis of formation of welded joints in the solid phase is based on the analysis of welded joints by scanning electron microscopy. Energy dispersive analysis of the welded joint zone did not reveal the diffusion of zinc into the AlMg2.5 alloy and magnesium into the B63 alloy. Energy dispersive analysis confirmed the assumption about the formation of a welded joint under conditions of wetting of molten metal by a pulsed electric arc, followed by displacement from the joint zone and plastic deformation of the heated metal. Recommendations are given for taking into account the polarity in high-voltage capacitor welding, depending on the thickness of the thinnest element.

Aprecierea potențialului morfogenetic și regenerativ al genotipurilor de triticale în cultura in vitro

Triticale is an important cereal crop grown throughout the world. Research showed that the regen-eration of young plants from mature embryos triticale depended on genotypic characteristics. The fre-quency of callusogenesis varied depending on the genotype and was: 188 TR5027 - 80.19%, Ingen 93 standard - 92.02% and Ingen 35 - 98.45%, and the frequency of rhizogenesis compared to embryogenesis proved to be high and constituted on average 57.35%. Only in 34.53% of the morphogenic callus, the de-velopment was of the embryoid type. The average frequency of regeneration was 35.07%. The dispersive analysis of the obtained results shows a significant influence of the genotype in establishing a positive callusogenetic response (P <0.001), the influence power being 76.04%.

On the Asymptotic Behavior of Solutions to the Vlasov–Poisson System

We prove small data modified scattering for the Vlasov–Poisson system in dimension $d=3$, using a method inspired from dispersive analysis. In particular, we identify a simple asymptotic dynamics related to the scattering mass.

OBTAINING MESOPHASE PITCHES FROM COAL TAR

This article presents the results of research on mesophase pitch production from coal tar. The preparation of mesophase pitch was carried out by heat treatment in an argon atmosphere at temperatures of 300, 350, and 400 °C. The resulting carbon pitches were analyzed by scanning electron microscopy, Raman spectroscopy, and energy-dispersive analysis. An increase in the degree of surface degradation and the number of mesophase centers per unit area was observed with an increase in the treatment temperature to 300 °C. At 350 °C, a transition from an isotropic to an anisotropic structure was observed, where the mesophase centers were about 2 μm in size. A similar anisotropic structure was observed for a sample of coal tar obtained at 400 °C, and in some areas, a layered structure was observed, which could be associated with an increase in the graphitization degree of the samples. The particle size of the mesophase increases to 3.5-5 microns. The results of energy dispersive analysis showed that an increase in temperature leads to a decrease in the sulfur content. At 400 °C, sulfur is completely removed from the coal tar pitch composition. A correlation between the heat treatment temperature and the structure of the obtained pitch was established.

Dispersive analysis of the Primakoff reaction $$\gamma K \rightarrow K \pi $$

We provide a dispersion-theoretical representation of the reaction amplitudes $$\gamma K\rightarrow K \pi $$ γ K → K π in all charge channels, based on modern pion–kaon P-wave phase shift input. Crossed-channel singularities are fixed from phenomenology as far as possible. We demonstrate how the subtraction constants can be matched to a low-energy theorem and radiative couplings of the $$K^*(892)$$ K ∗ ( 892 ) resonances, thereby providing a model-independent framework for future analyses of high-precision kaon Primakoff data.