Radiation-induced stable radicals in calcium phosphates: Results of multifrequency epr, ednmr, eseem, and endor studies

This article presents the results of a study of radiation-induced defects in various synthetic calcium phosphate (CP) powder materials (hydroxyapatite—HA and octacalcium phosphate—OCP) by electron paramagnetic resonance (EPR) spectroscopy at the X, Q, and W-bands (9, 34, 95 GHz for the microwave frequencies, respectively). Currently, CP materials are widely used in orthopedics and dentistry owing to their high biocompatibility and physico-chemical similarity with human hard tissue. It is shown that in addition to the classical EPR techniques, other experimental approaches such as ELDOR-detected NMR (EDNMR), electron spin echo envelope modulation (ESEEM), and electronnuclear double resonance (ENDOR) can be used to analyze the electron–nuclear interactions of CP powders. We demonstrated that the value and angular dependence of the quadrupole interaction for14 N nuclei of a nitrate radical can be determined by the EDNMR method at room temperature. The ESEEM technique has allowed for a rapid analysis of the nuclear environment and estimation of the structural positions of radiation-induced centers in various crystal matrices. ENDOR spectra can provide information about the distribution of the nitrate radicals in the OCP structure. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Published under the CC BY 4.0 license.Authors would like to thank the Russian Foundation for Basic Research, project no. 18-29-11086. Institute of Solid State Physics, University of Latvia as the Center of Excellence received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01–2016-2017- TeamingPhase2 under grant agreement No. 739508, project CAMART2

Prediction of Target Erosion for Planar Magnetron Sputtering Systems

Based on the analysis of the correlation between plasma glow and the magnetic field over a magnetron target, a model for predicting the shape of the target erosion of MSS is proposed. The magnetic field distribution is obtained upon direct measurement or calculation using the ELCUT software, which allows one to calculate the magnetic field based on the magnetron model. A special software has been developed for the calculation of the depletion profile of a target in a planar MSS. It allows one to predict the target erosion during the design phase of MSS, thus reducing the efforts required for designing a multi-magnet system of magnetron. The software has to be tested by comparing the calculated profile of the target erosion with the real one for different types of MSS

The Mutual Incorporation of Mg²⁺ and CO₃²⁻ into Hydroxyapatite: A DFT Study

Hydroxyapatite (HA) with a stoichiometry composition of Ca10(PO4)6(OH)2 is widely applied for various biomedical issues, first of all for bone defect substitution, as a catalyst, and as an adsorbent for soil and water purification. The incorporation of foreign ions changes the acid–base relation, microstructure, porosity, and other properties of the HA materials. Here, we report the results of calculations of the density functional theory and analyze the possibility of two foreign ions, CO32− and Mg2+, to be co-localized in the HA structure. The Na+ was taken into account for charge balance preservation. The analysis revealed the favorable incorporation of CO32− and Mg2+ as a complex when they interact with each other. The energy gain over the sole ion incorporation was pronounced when CO32− occupied the A position and Mg2+ was in the Ca(2) position and amounted to -0.31 eV. In the most energy-favorable complex, the distance between Mg2+ and the O atom of carbonate ion decreased compared to Mg…O distances to the surrounding phosphate or hydroxide ions, and amounted to 1.98 Å. The theoretical calculations agree well with the experimental data reported earlier. Understating the structure–properties relationship in HA materials varying in terms of composition, stoichiometry, and morphology paves the way to rational designs of efficient bio-based catalytic systems

Mechanisms of higher school development in the paradigm of its global competitiveness (on the example of the kazan federal university)

The study examines the mechanisms for assessing the competitiveness of universities in accordance with various methodological approaches used in the system of international rankings; determines the degree of convergence of the rankings in question both in integral and in private performance assessments, and identifies the most significant indicators on this basis, followed by focusing some tools, mechanisms and directions to improve the competitiveness of Russian universities on them. Particular attention is paid to the identification of regional features of the territories that form the potential and direction of development of federal universities, adapted to the existing competitive advantages.The method of works conduct is based on the use of tools for econometric analysis of the evaluation of the convergence of international academic rankings (ARWU (The Academic Ranking of World Universities), THE (Times Higher Education), QS (Quacquarelli Symonds)) by determining the values of Spearman ratios, as well as tools of statistical analysis and other special methods that help define and search for key areas for the development of federal universities that ensure the growth of their global competitiveness.The novelty of study consists in the developed conceptual approach of determining the key directions of the development of universities of the Russian Federation taking into account the assessment of their global competitiveness, as well as relying on territorial aspects and peculiarities of their functioning