Structure and phase composition of the superalloy on the basis of Ni-Al-Cr alloyed by Re and La

Qualitative and quantitative studies of the structure, phase composition, morphology of phase of the high-rhenium alloys additionally doped with La were carried out by TEM and SEM methods. The alloy was obtained by directional solidification method. It was shown that introduction of Re and La to an alloy leads to formation of new phases: [beta] and [chi] , which bring serious irregularities in the structure of quasicuboids of [gamma]'-phase

The structure of heat-resisting alloy modified by thermal treatment and alloyed by rhenium and lanthanum

The paper presents the scanning and transmission electron microscope investigations of the structure, phase composition, and morphology of heat-resisting alloy modified by thermal treatment and additionally alloyed by rhenium and lanthanum. Rhenium alloy is obtained by the directional crystallization technique. The structural investigations are carried out for three alloy states, i.e. 1) original (after the directional crystallization); 2) 1150°С annealing during 1 h and 1100°С annealing during 480 h; 3) 1150°С annealing during 1 h and 1100°С annealing during 1430 h. It is shown that fcc-based [gamma]- and [gamma]'-phases are primary in all states of the alloy. [gamma]'-phase has L12 structure, while [gamma]-phase is a disordered phase. Rhenium and lanthanum are phase-forming elements. Investigations show that high-temperature annealing modifies the structural and phase conditions of the heat-resisting alloy

The structure of heat-resisting alloy modified by thermal treatment and alloyed by rhenium and lanthanum

The paper presents the scanning and transmission electron microscope investigations of the structure, phase composition, and morphology of heat-resisting alloy modified by thermal treatment and additionally alloyed by rhenium and lanthanum. Rhenium alloy is obtained by the directional crystallization technique. The structural investigations are carried out for three alloy states, i.e. 1) original (after the directional crystallization); 2) 1150°С annealing during 1 h and 1100°С annealing during 480 h; 3) 1150°С annealing during 1 h and 1100°С annealing during 1430 h. It is shown that fcc-based [gamma]- and [gamma]'-phases are primary in all states of the alloy. [gamma]'-phase has L12 structure, while [gamma]-phase is a disordered phase. Rhenium and lanthanum are phase-forming elements. Investigations show that high-temperature annealing modifies the structural and phase conditions of the heat-resisting alloy

Formation structural phase gradients in rail steel during long-term operation

The paper presents results of the structural and phase analysis of the surface layer composition in the type R65 rail steel in its original state and after long-term operation. It is shown that long-term operation of rail steel is accompanied by its structural and phase modification at a depth of not less than 2 mm. The structural elements are detected that can be stress concentrators

Accounting of motivators and demotivators under introduction of the brc system

Рассматривается необходимость учета демотиваторов при работе с балльно-рейтинговой системой оцениванияThe article considers the need to take into account demotivators when working with the BRS syste

Nitriding of titanium in electron beam excited plasma in medium vacuum

We report our results on nitriding of industrially-pure titanium VT1-0 in the plasma formed by continuous electron beam created by a fore-vacuum plasma-cathode electron source, at different temperatures of the titanium sample surface (700–1020 °C) and electron beam energy (4–6 keV), in medium vacuum (5 Pa) of nitrogen. Electron beam was used for direct treatment and heating of the sample as well as for the plasma generation. It is demonstrated that such parameters of the Ti sample as nitrogen content, the depth of nitride layer, Vickers microhardness, and wear-resistance grow with sample temperature and beam energy. Such positive effects happen, likely, due to enhanced generation of active atoms and atomic ions of nitrogen in beam-produced plasmas in medium vacuum

A Mathematical model for Astrocytes mediated LTP at Single Hippocampal Synapses

Many contemporary studies have shown that astrocytes play a significant role in modulating both short and long form of synaptic plasticity. There are very few experimental models which elucidate the role of astrocyte over Long-term Potentiation (LTP). Recently, Perea & Araque (2007) demonstrated a role of astrocytes in induction of LTP at single hippocampal synapses. They suggested a purely pre-synaptic basis for induction of this N-methyl-D- Aspartate (NMDA) Receptor-independent LTP. Also, the mechanisms underlying this pre-synaptic induction were not investigated. Here, in this article, we propose a mathematical model for astrocyte modulated LTP which successfully emulates the experimental findings of Perea & Araque (2007). Our study suggests the role of retrograde messengers, possibly Nitric Oxide (NO), for this pre-synaptically modulated LTP.Comment: 51 pages, 15 figures, Journal of Computational Neuroscience (to appear

Formation of students' scientific thinking based on the learning of methods of the substance analysis

Introduction. In Federal State Standards of the Higher Education (FSS HE) of the natural-science and technical specialties and also in a number of the corresponding professional standards, the competence in the field of analytical chemistry is specified as one of the main qualification characteristics of an expert/university graduate. It is caused by interdisciplinarity of analytical chemistry and a wide range of application of analysis methods which are used today not only directly on chemical production, but also in power engineering, construction engineering, metallurgy, materials science, standardization, certification, and many other spheres. At the current time, however, there is a big gap between achievements of chemical science and content of high school discipline that reduces quality of staff training demanded in labour market. This discrepancy is caused both by preservation of traditional methodology of teaching chemistry and the reasons of the methodical plan. The aim of the publication is to search for more effective and productive ways of mastering the educational material that is relevant for acquiring the qualifications required from the university graduate. Methodology and research methods. Methodological framework of the article involves the concepts of chemical and natural-science education at the higher school; the principles of the system-based, cognitive, practice-focused and competence-based training. Results and scientific novelty. On the basis of the review and generalization of scientific and methodological resources on the theory and practice of application of the analysis methods of substances from didactic positions, a number of these methods have been singled out and compared; their role and features in determination of a molecule structure and other characteristics of an individual substance and its solutions have been shown. Despite the fact that the work is carried out using known methods of analysis, such a generalization makes it possible to more clearly understand the principles of the choice of a method and the method importance according to the purposes and specifics of the studied object that is essential for formation of research skills during training, as well as for formation of scientific thinking and the required qualification acquisition by graduates of the natural-science and technical specialties. In order to update the acquired knowledge, the examples illustrating applied use of various analysis methods in modern research and production practice have been collected. Tables have been made for a faster perception of the material by methods of analysis for the purpose of an informed choice of the method. Reliance on the principle of tabular collection of material makes it easier to understand the individuality of the method; allows teachers to reduce their workload; and on the part of students, to shorten the time and simplify the procedure of choosing the method of chemical, physicochemical and/or physical analysis. Practical significance. The work is compiled in accordance with the State General Educational Standards of Higher Professional Education, and can be recommended to practising and beginning teachers of higher education institutions, as well as graduate students of chemical specialties. The materials presented in the article can assist in designing the curricula of chemical disciplines or modules of educational programs. © 2018 Obrazovanie i Nauka. All rights reserved