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Polyhedrons in which every integral point belonging to them is a vertex are studied. [ABSTRACT FROM AUTHOR]

Polyhedrons in which every integral point belonging to them is a vertex are studied. [ABSTRACT FROM AUTHOR]

The paper describes the effect of the addition of alumina nanofibers on the mechanical properties of the epoxy resin. Alumina nanofibers functionalized with epoxypropyl functional groups are used in this work. The dependence of the mechanical characteristics on the amount of the additive, as well as the features of its distribution in the material, is investigated. In the work, nanocomposites were obtained, which are epoxy resin with aluminum oxide nanofibers. The mechanical properties of the samples were studied by bending tests and differential mechanical analysis (DMA). It has been shown that the addition of alumina nanofibers leads to an increase in ultimate flexural strength. The maximum of this increase is near the percolation threshold of alumina nanofibers in epoxy resin. With the addition of 0.2% alumina nanofibers, the ultimate flexural strength increases from 41 to 71 MPa. It is shown that after exceeding the percolation threshold of nanofibers, the ultimate strength decreases. In this case, the elastic modulus increases from 0.643 to 0.862 GPa. DMA is shown that the glass transition temperature decreases with increasing amount of the additive. This indicates a decrease in the molecular weight of the polymer. By implication, this suggests that the hardener connects the epoxypropyl functional groups on the nanofibers and the epoxy groups in the resin, and as a result of this process, the nanofibers become natural polymer chain length limiters. The data obtained from mechanical testing and differential mechanical analysis can be used to strengthen epoxy resins in polymer composite materials and molding compositions. [ABSTRACT FROM AUTHOR]

The article considers the current problem of helium-3 supply constraints for industry and science. The projected 3He shortage is approximately 55000 liters (at 1 atm and 20°С) in the world production market. Tritium is the only industrial 3He source. Alternative sources of 3He are discussed in this paper. Between 25 and 50% of the 3Не shortage could be addressed with natural gas extraction. To obtain high purity 3He gas, low-temperature methods of separation (superfluid filtration, rectification and adsorption) are promising. The 3He lunar mining operation could cover the entire worldwide shortage, but this is not a perspective over the next fifteen-twenty years. The controlled thermonuclear fusion is both an energy source and a new 3He production alternative source. Between 10 and 25% of the 3He shortage could be covered with this technology. The high molar concentration of 3He in the obtained mixtures will make it possible to extract the rare isotope by the method of low-temperature adsorption with subsequent enrichment by the method of low-temperature rectification. [ABSTRACT FROM AUTHOR]

The content and profile distribution of 137Cs in iron-illuvial dwarf and shallow-podzolic podzols (Albic Podzols) under bilberry-lichen and green-lichen-bilberry pine forests in the located near the Kola Nuclear Power Plant have been analyzed. The pollution density (reserve) of 137Cs in the root-inhabited layer (0–30 cm) in the studied soils was significantly lower than the established control level of 37 000 Bq/m2 and amounts to 530–2459 Bq/m2. A significant part of 137Cs (60 to 90%) was concentrated in mineral horizons. It has been shown that the pollution density of 137Cs in the observation zone of a nuclear power plant was mainly due to global fallout. The greatest influence on 137Cs accumulation in the studied soils was exerted by the organic matter reserve. [ABSTRACT FROM AUTHOR]