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The impact of the focusing current of electron beam welding on the nature of the formation of welded joints of aluminium 2219 alloy was investigated. It was established that when the focusing current increases, the width of the facial weld grows. And the width of the weld root depends on the real position of the electron beam focus relative to a sharp focus on the metal surface (639 mA). Dependence of the focusing current on the distribution of copper and aluminium in the weld metal was revealed. An increase in the focusing current from 629 to 649 mA led to an increase in the copper content in the interdendritic regions. Energy dispersion X-ray analysis showed that the microstructure of the welded joint produced at the focusing current of 629 mA, consists of equiaxial dendrites with embedded small particles, pores and α+θ-Al2 Cu eutectic, separated in the interdendritic regions. [ABSTRACT FROM AUTHOR]

It is known that soil streptomycetes are active producers of a wide range of biologically active substances, including antibiotics. Since the issue of the relationship between the antibiotics synthesis and the ways of other biologically active substances synthesis is not studied in full at present, the research subject is relevant. The question is not fully investigated. The goal of the work was to research the correlation dependence between the biosynthesis of antibiotic and other biologically active substances produced by soil streptomycetes. Methods. To determine the relationship between the synthesis of antibiotic compounds and other biologically active substances by soil streptomycetes was held factorial analysis with using the method of the main components; for identification the coefficients of regression and dispersion analysis were used the package Statistika v.10.0 (StatSoft. Inc., USA) and Mathlab v . 6.0; cluster analysis was held by using the Ward method with determination Euclidean distance as the degree of difference (in%) between the estimated variables. Results. Correlation relations between the antibiotic synthesis by strains Streptomyces violaceus IMV Ac-5027 and S. netropsis IMV Ac-5025 with biosynthetic pathways of other biologically active substances, but with different links are identificated. Synthesis of polyene and anthracycline antibiotics correlates with the synthesis of phytohormones (indole-3-carbinol, indole-3-carboxylic acid, isopentynyladenosine and gibberellins) and sterols (sitosterol). Production of these antibiotics also shows the dependence in the synthesis of triglycerides, sterols and their esters and fatty acids (isopalmitin, heptadecene, stearic fat acid, oleic fat acid, peanut fat acid). These antibiotics synthesis does not have a direct relationship with the content of amino acids. Conclusions. The relationships between biosynthesis of antibiotics, phytohormones and steroid compounds by soil streptomycetes S. netropsis IMV Ac-5025 and S. violaceus IMV Ac-5027 provides new tools for understanding the complex interconnections associated with the optimization of the synthesis of industrially important metabolites. Thus we can broad the knowledge about the conditions of their formation, the biosynthesis ways and functional significance for microbial cells. [ABSTRACT FROM AUTHOR]

Iron nanoparticles show great reactivity in the remediation of groundwater and soil or other environmental applications, however, the persistence and dispersion of iron nanoparticles need to be improved. In this study, palygorskite and hexadecyl trimethylammonium modified palygorskite were used to support iron nanoparticles. The electron microscopic study of the obtained materials is performed. Iron nanoparticles had a core–shell structure with the core being iron, and the shell consisting of iron (hydr)oxides were detected by X-ray diffraction patterns. The sorption of uranium(VI) and cobalt(II) ions from contaminated waters using nanodispersed reactive active material on the basis of modified surfactant of clay mineral were investigated. The reduction of U(VI) and Co(II) was highest with HDTMA-palygorskite/iron particles, followed by palygorskite/iron particles and free iron nanoparticles. It has been shown that the efficiency of removal of metal ions is substantially influenced by the pH of the aqueous medium, the content of surfactant and the amount of immobilized nanosized Fe0 on the surface of the palygorskite. The influence of iron in the composite on its sorption properties was investigated. It has been found that the optimum content of Fe in the composite for the extraction of Co(II) and U(VI) ions from aqueous solutions is 10 % of the mass of the sorbent. The processes of aging of composites and loss of reactivity with respect to Co(II) ions are studied. The possibility of their use in the purification of groundwater with the use of modern environmental technologies is shown. It has been found that the composite sorbent exhibits the best sorption properties in relation to both uranium(VI) and cobalt(II), rather than pure nanosized iron, due to the increase of its dispersion due to the decrease in the agglomeration of nanosized iron particles and the increase in the specific surface area of the modified specimens. The presence of organo-palygorskite apparently decreased the extent of aggregation and the size of the iron particles. The prospect of using composites based on palygorskite and organopalygorskite with a layer applied Fe0 for the effective removal of heavy metal ions and radionuclides from aqueous media has been established. [ABSTRACT FROM AUTHOR]

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The influence of the obtaining way of nanostructured epoxyurethane olygomers (nEUO) on molecular characteristics and the structure of epoxyurethanes on its base was investigated. It is shown, that size and dispersion of SiO₂ -- particles are determined by amount of tetraethoxysilane (TEOS) and of its obtaining way. The influence of concentration of TEOS on organic and inorganic components formation in epoxyurethane matrix was established. Molecular characteristics of net epoxyurethane oligomer (EUO) and nEUO were evaluated by exclusion liquid chromatography. Features of formed structure of epoxyurethane were evaluated by optical method. [ABSTRACT FROM AUTHOR]

We investigate mechanical properties of complex alloys with eutectic (α-Al-Mg2Si) structure for high-temperature application. Specimens are annealed at the temperature of 300 °C during 5 hours to obtain uniformly distributed dispersed Al3(Sc1-xZrx) nanoparticles in α-Al phase. Investigation of mechanical properties of alloys with different content of eutectic component by a tension method is carried out in the interval of temperatures 20-400 °C with speed of 10-3 s-1. The content of eutectic compound is determined by metallographic method. The alloys microstructure with different eutectic content is studied and fractography analysis is conducted. We determine the fracture mechanism and main factors that have an influence on strength and plasticity at different temperatures. Experimental results enable to optimize alloys composition and obtain the best combination of strength and plasticity for different applications. Alloys under consideration have yield strength of ³ 100 MPa at the temperature of 400 °C. Alloys that contain more than 30 vol. % of eutectic compound necessary for good casting properties are competitive comparing to the best existing cast aluminum alloys. [ABSTRACT FROM AUTHOR]