A continual model of a damaged medium used for analyzing fatigue life of polycrystalline structural alloys under thermal–mechanical loading

The main physical laws of thermal–plastic deformation and fatigue damage accumulation processes in polycrystalline structural alloys under various regimes of cyclic thermal–mechanical loading are considered. Within the framework of mechanics of damaged media, a mathematical model is developed that describes thermal–plastic deformation and fatigue damage accumulation processes under low-cycle loading. The model consists of three interrelated parts: relations defining plastic behavior of the material, accounting for its dependence on the failure process; evolutionary equations describing damage accumulation kinetics; a strength criterion of the damaged material. The plasticity model based on the notion of yield surface and the principle of orthogonality of the plastic strain vector to the yield surface is used as defining relations. This version of defining equations of plasticity describes the main effects of the deformation process under monotone cyclic, proportional and nonproportional loading regimes. The version of kinetic equations of damage accumulation is based on introducing a scalar parameter of damage degree and energy principles, and account for the main effects of nucleation, growth and merging of microdefects under arbitrary regimes of low-cycle loading. The strength criterion of the damaged material is based on reaching a critical value of the damage degree. The results of numerically modeling cyclic thermal–plastic deformation and fatigue damage accumulation in heat-resistant alloys (Nimonic 80A, Haynes 188) under combined thermal–mechanical loading are presented. Special attention is paid to the issues of modeling the processes of cyclic thermal–plastic deformation and fatigue damage accumulation for complex deformation processes accompanied by the rotation of the main stress and strain tensor areas. It is shown that the present damaged medium model accurately enough for engineering purposes describes the processes of cyclic isothermal and nonisothermal deformation and fatigue damage accumulation under combined thermal–mechanical loading and makes it possible to evaluate low-cycle fatigue life of heat-resistant alloys under arbitrary deformation trajectories

Raman and Infrared-Active Phonons in Hexagonal HoMnO3_3 Single Crystals: Magnetic Ordering Effects

Polarized Raman scattering and infrared reflection spectra of hexagonal HoMnO$_3$ single crystals in the temperature range 10-300 K are reported. Group-theoretical analysis is performed and scattering selection rules for the second order scattering processes are presented. Based on the results of lattice dynamics calculations, performed within the shell model, the observed lines in the spectra are assigned to definite lattice vibrations. The magnetic ordering of Mn ions, which occurs below T$_N$=76 K, is shown to effect both Raman- and infrared-active phonons, which modulate Mn-O-Mn bonds and, consequently, Mn exchange interaction.Comment: 8 pages, 6 figure

Solvability of singular integral equations with rotations and degenerate kernels in the vanishing coefficient case

By means of Riemann boundary value problems and of certain convenient systems of linear algebraic equations, this paper deals with the solvability of a class of singular integral equations with rotations and degenerate kernel within the case of a coefficient vanishing on the unit circle. All the possibilities about the index of the coefficients in the corresponding equations are considered and described in detail, and explicit formulas for their solutions are obtained. An example of application of the method is shown at the end of the last section

Interaction in the Systems with Tl(І), Hg(ІІ), Pb(ІІ), Si(IV).

Методами РФА та ДТА досліджено фазові рівноваги у квазіпотрійних системах Tl2Х–{Hg, Pb}X–SiX2 (X – S, Se). Установлено існування нових тетрарних еквімолярних сполук. Методом порошку розшифровано кристалічну структуру Tl2HgSiSe4 (ПГ I-42m) та Tl2PbSiS4 (ПГ P21/a). The phase equilibria of the quasi-ternary systems Tl 2Х–{Hg, Pb}X–SiX2 (X – S, Se) were investigated by X-ray phase analyse and DTA. New quaternary phases with equil ratio components were found in these systems. Crystal structures of Tl2HgSiSe4 (S. G. I-42m) and Tl2PbSiS4 (S. G. P21/a) were determinated by X-ray powder diffraction

РАДІОЗАХИСНІ ВЛАСТИВОСТІ 2-МЕРКАПТОБЕНЗОТІАЗОЛУ НА КЛІТИНИ IN VITRO

Aim: to study the radioprotective properties of 2-merсaptobenzothiazole on proliferating cell culture test system.Material and Methods. Cytological, statistics.Results. Upon the incubation of inoculated cellline L929 with 2-merсaptobenzothiazole in the concentration range 0.03–3.00 µg/mL statistically significant change (p≤0.05) of cell population density in mono layer cultures was not found. At the same time for all the applied reagent concentrations stimulation of mitotic activity in the terminal (5th day) stage of cultivation was observed. Exposure of cells by gamma-quanta of 60Co in doses of 1, 5 and 10 Gyled to dose-dependant morphological changes in cell culture. The irradiation of cells in the presence of 2-mercaptobenzothiazole significantly reduced the negative effect of radiation on the indicators of vitality of cells and their differentiation in culture.Conclusions. Quantitative evaluation of radioprotective properties of 2-mercaptobenzothiazole in the test systems of culture of myogenic cells as well as in the L929 line (fibroblast cells) revealed that the highest coefficients of protection (0.31–0.36) and maximum level of factor of dose reduction (4) were observed at 3 mg/ml reagent concentration (irradiation dose – 1 Gy). According to the literature data and our research results, 2-mercaptobenzothiazole might be considered as a reagent with radioactive properties for cells in vitro.Целью работы было исследование радиопротекторных свойств 2-меркаптобензотиазола в тест-системах первичной и перевиваемой культур пролиферирующих клеток.Материал и методы. Использовали цитологические и статистические методы.Результаты. При инкубации перевиваемых клеток линии L929 с 2-меркаптобензотиазолом в диапазоне концентраций 0,03–3,00 мкг/м не было выявлено статистически достоверного изменения (р≤0,05) плотности клеточной популяции в монослойных культурах. В то же время наблюдали для всех примененных концентраций реагента стимуляцию митотической активности на терминальной (5 сутки) стадии культивирования. Облучение клеток гамма-квантами 60Со в дозах 1, 5 и 10 Гр привело к дозозависимым морфофункциональным изменениям в культуре клеток. Облучение клеток в присутствии 2-меркаптобензотиазола существенно уменьшило негативное влияние радиации на показатели жизнеспособности клеток и их дифференциацию в культуре.Выводы. Количественная оценка радиопротекторных свойств 2-меркаптобензотиазола в тест-системах культуры миогенных клеток и линии L929 (фибробластоподобные клетки) показала, что наивысшие показатели коэффициента защиты (0,31–0,36) реагент показал при концентрации 3 мкг/мл при облучении в дозе 1 Гр, а фактор уменьшения дозы был максимальный – 4, при концентрации 3,00 мкг/мл. По совокупности данных литературы и результатов собственных исследований можно считать 2-меркаптобензотиазол реагентом с радиопротекторными свойствами для клеток in vitro.Метою роботи було дослідження радіопротекторних властивостей 2-меркаптобензотіазолу у тест-системах первинної та перещеплюваної культур проліферуючих клітин.Матеріал і методи. Використовували цитологічні і статистичні методи.Результати. При інкубації перещеплюваних клітин лінії L929 з 2-меркаптобензотіазолом у діапазоні концент­рацій 0,03–3,00 мкг/м не було виявлено статистично достовірної зміни (р≤0,05) щільності клітинної популяції у моношарових культурах. Водночас спостерігали для усіх застосованих концентрацій реагенту стимуляцію мітотичної активності на термінальній (5 доба) стадії культивування. Опромінення клітин гамма-квантами 60Со в дозах 1, 5 та 10 Гр призвело до дозозалежних морфофункціональних змін у культурі клітин. Опромінення клітин у присутності 2-меркаптобензотіазолу істотно зменшило негативний вплив радіації на показники життєздатності клітин та їх диференціацію в культурі.Висновки. Кількісна оцінка радіопротекторних властивостей 2-меркаптобензотіазолу у тест-системах культури міогенних клітин та лінії L929 (фібробластоподібні клітини) показала, що найвищі показники коефіцієнта захисту (0,31–0,36) реагент показав при концентрації 3 мкг/мл при опроміненні в дозі 1 Гр, а фактор зменшення дози був максимальний – 4, за концентрації 3,00 мкг/мл. За сукупністю даних літератури та результатів власних досліджень можна вважати 2-меркаптобензотіазол реагентом із радіопротекторними властивостями для клітин in vitro

TESTING POTATO COLLECTION SAMPLES FOR THE PRESENCE OF GENES FOR RESISTANCE TO PHYTOPATHOGENS BY MEANS OF DNA MARKERS

The development of phytopathogen-resistant varieties is the most reliable and economic way to reduce potato yield losses. Breeding of such varieties is possible by using genetic sources of resistance. The use of DNA markers for identification of valuable genotypes, including forms with several resistance genes, makes it possible to significantly improve breeding efficiency. The development of a multiplex PCR technique and using it to simultaneously test varieties and breeding lines for several genes that control the resistance to viruses and nematodes is a new approach to using DNA markers. This study is aimed at screening samples from the collection of the Narym Department of  Breeding and Seed Production of the Siberian Research Institute of Agriculture and Peat (the Branch of the Siberian Federal Agrobiotechnology Research Center, the Russian Academy of Sciences) using the multiplex PCR technique, for genes for resistance to Globodera rostochiensis and Globodera pallidas, potato wart disease, viruses X and Y. 40 samples were tested by means of genetic markers to identify genes for resistance to potato wart disease (Sen1), virus X (Rx), virus Y (Ryadg, Rychc, Rysto), Globodera rostochiensis (H1, Gro1-4) and Globodera pallida (Gpa2), in the genome. The sample included two varieties, three populations produced by self-pollination of the Ideal variety, and 35 individually selected potato hybrids. As a result, we identified marker NL25 (Sen1) in 19 samples; marker PVX (Rx) in 13 samples; marker RYSC3312 (Ryadg) in 10 samples; marker YES3-3A341 (Rysto) in 5 samples; markers TG 689141, 57R450, N195337 (H1) in 12 samples; marker Gro1-4-1602 (Gro1-4) in 6 samples; marker Gpa2-2452 (Gpa2) in 13 samples. In terms of economically valuable traits, sample С-31-15 is noted for high yield and quality indicators. It carries genes for resistance to potato virus X (Rx), Y (Rysto), Globodera rostochiensis (H1, Gro1-4), and Globodera pallida (Gpa2)

A study of the superconducting gap in RNi2_2B2_2C (R = Y, Lu) single crystals by inelastic light scattering

Superconductivity-induced changes in the electronic Raman scattering response were observed for the RNi$_2$B$_2$C (R = Y, Lu) system in different scattering geometries. In the superconducting state, 2$\Delta$-like peaks were observed in A$_{1g}$, B$_{1g}$, and B$_{2g}$ spectra from single crystals. The peaks in A$_{1g}$ and B$_{2g}$ symmetries are significantly sharper and stronger than the peak in B$_{1g}$ symmetry. The temperature dependence of the frequencies of the 2$\Delta$-like peaks shows typical BCS-type behavior, but the apparent values of the $2\Delta$ gap are strongly anisotropic for both systems. In addition, for both YNi$_2$B$_2$C and LuNi$_2$B$_2$C systems, there exists reproducible scattering strength below the $2\Delta$ gap which is roughly linear to the frequency in B$_{1g}$ and B$_{2g}$ symmetries. This discovery of scattering below the gap in non-magnetic borocarbide superconductors, which are thought to be conventional BCS-type superconductors, is a challenge for current understanding of superconductivity in this system.Comment: Added text, changed a figure, and added references. Will appear in Phys. Rev.

Fermi Resonance in Phonon Spectra of Quaternary Chalcohenides of the type Cu2ZnGeS4

The experimental resonant and non-resonant Raman scattering spectra of the kesterite structural modification of Cu2ZnGeS4 single crystals are reported. The results are compared with those calculated theoretically within the density functional perturbation theory. For the majority of lines a good agreement (within 2–5 cm−1) is established between experimental and calculated mode frequencies. However, several dominant spectral lines, in particular the two intense fully symmetric modes, are found to deviate from the calculated values by as much as 20 cm−1. A possible reason for this discrepancy is found to be associated with the Fermi resonant interaction between one and two-phonon vibrational excitations. The modelling of spectra, which takes into account the symmetry of interacting states, allows a qualitative description of the observed experimental findings. Due to the similarity of the vibrational spectra of Cu2A II B IV S4 (A  =  Zn, Mn, Cd; B  =  Sn, Ge, Si) chalcogenides, Fermi resonance is argued to be a general phenomenon for this class of compounds