Vol 16, No 4 (2020)

Solid solutions of the YCuxMn1−xO3 system have been synthesized at x = 0.00, 0.05, 0.10, 0.15 with the use of preliminary mechanical activation. Studies of the structure and microstructure of the obtained samples have been carried out. The temperature changes in the conductivity of the manufactured objects have been partially studied. Based on X-ray diffraction analysis, it was found that mechanical activation practically completely excludes the formation of a hexagonal phase upon the addition of Cu. In this case, the perovskite phase is formed. In the composition without copper, a hexagonal phase is formed, but its amount is comparable to the orthorhombic non-perovskite phase. The presence of the latter is noted throughout the study interval. The study of the microstructure showed the presence of nanocrystalline fouling of grains. Unlike pure YMnO3, in compositions doped with copper, grains with and without fouling have approximately the same size scatter. It is noted that, as in the case of using the method of conventional ceramic technology, synthesis with preliminary mechanical activation occurs with the presence of liquid phases. The microstructure photographs of all samples with x > 0 clearly show local intergranular adhesions. A study of the electrical resistivity ρ at T = 300–700 K revealed an anomaly that shifts to the low-temperature region with an increase in the copper concentration. Presumably, this anomaly is associated with structural rearrangements preceding the high-temperature phase transition. In the hexagonal state of YMnO3, it consists in the inclination and rotation of oxygen bipyramids, and in the orthorhombic state, in the orbital ordering and rotation of oxygen octahedra. The research results will be useful in the study of solid solutions made with the use of mechanical activation.

The coastline in Surabaya, Indonesia is about 47.4 kilometers and lies in twenty city subdistricts. One of the main problems in coastal Surabaya is bank erosion. This process has a negative impact on the coastal infrastructure and residential areas of the city, and leads to the degradation of natural landscapes such as mangroves area in Surabaya. The aim of this research was to study the modern coastal processes of the Surabaya coast and analyze the geomorphological changes for the period from 1994 to 2018. Data used in this research were from Landsat TM 5 1994 (8 July 1994) and Landsat 8 OLI 2018 (17 May 2018) and coastal field surveys. The method was the spatial-temporal analysis of the coastline position for twenty-four years (1994–2018) by combining satellite images and conducting sub-satellite observations. In 1994–2018, coastal erosion was recorded in some sub-districts: Tambak Osowilangun, Tambak Langon, Greges and Kalianak (West Surabaya); Moro Krembangan, Ujung, Bulak Banteng, and Kedung Cowek (North Surabaya); Keputih, and Wonorejo and Medokan Ayu (East Surabaya). The most intense coastal retreat (erosion) was observed in the Wonorejo sub district (about 141637.1 m2). Measures that have been taken by the community of Wonorejo was the planting of mangrove trees. The area of man-made coasts increased due to the construction of the new port of Teluk Lamong by 916068.3 m2.

The article presents the results of the research of taxonomic composition and level of quantitative development of phytoplankton on the Northeastern Black Sea shelf, Utrish region in different seasons of 2015–2019. One hundred and nine species of phytoplankton belonging to 7 divisions were found. The greatest species diversity was observed among dinophytes (57 species) and diatoms (38 species). The average values of quantitative development of planktonic algae in the study period were 2156 thousand cells/l and 126 mg/m3. The lowest values of abundance (9.3 thousand cells/l) were marked in June 2015. The highest values (4566–6644 thousand cells/l) were found in the autumn period of 2016–2017. In May-June 2017, the phytoplankton abundance (660–757 thousand cells/l) were ten times less than the maximum values. Relatively high biomass values (127–240 mg/m3) were observed in the spring and summer (May, June) of 2015 and 2017. The values of phytoplankton biomass in the autumn season (September-November) 2016–2017 (32–55 mg/m3) were the lowest for the entire study period. To the greatest extent, this was facilitated by the development of small-cell phytoplankton species. Diatoms were the dominant division of algae: on average, they made up 40 (12–99) % of the total population and 34 (7–74) % of the biomass. Dinophytes formed 24 (0.7–85) % of the total population and a significant part of 51 (24–89) % of the phytoplankton biomass. The maximum development of Emiliania huxleyi was observed in the spring-summer period of 2017, when it accounted from 42 to 71 % of total abundance and 26 to 52 % of the phytoplankton biomass.

The article presents the results of studying the phenology of Opuntia engelmannii var. lindheimeri in the “Cape Martyan” Protected Area, as well as the assessment of the influence of abiotic factors (air temperature, duration of sunshine, precipitation) on the seasonal rhythms of plant development according to research data 2017–2019. It was found that in the South Coast of Crimea Opuntia species passes all phases of seasonal development, the nature of phenological development refers to extensive vegetating (185–215 days), spring-summer-autumn green plants, with a period of winter dormancy, with early spring awakening period, short period of flowering for 10–31 days (in June) and a long fruits ripening period – 53–89 days (September-November), whereas in North America, flowering occurs in June-July, fruiting in July-September. The results of dispersion, correlation and regression analyses showed that the duration of sunshine in the conditions of the South Coast of Crimea affects all phases of seasonal development, while the greatest complex influence of three factors was found for the phases “beginning of flowering” and “beginning of fruit coloring”. With further climate warming, there is a high probability of distribution of the Opuntia species at other natural zones of the Crimean Peninsula.

The boreal mollusk Mya arenaria Linnaeus, 1758 acclimatized to the Sea of Azov in 1977, and is found everywhere on sandy and silty ground. Until 2005, in Taganrog Bay, it was recorded in the westernmost part, forming small accumulations with a low biomass. From 2005 to 2016, it was not recorded in this area. Due to the annual increase in salinity, the distribution of the range to the east began in 2016. At the beginning of the expansion, Mya arenaria Linnaeus, 1758 was found only on the Dolgaya Spit with a biomass of 2.6 g/m2, and by 2019 it was found almost everywhere up to the Krivaya Spit with a biomass of up to 756 g/m2.