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Abstract—The cyanobacterial communities of Pskov Lake were studied in different seasons of 2021, and a comparison was made with data of 2018–2020. Information on the taxonomic composition and quantitative characteristics of cyanobacteria was obtained, and the species toxic to living organisms were demonstrated. A total of 196 species taxa of phytoplankton were registered at four permanent stations of the lake, 15.8% of which accounted for cyanobacteria. The cyanobacterial communities were most similar in terms of species in the summer and autumn periods. The quantitative indices of cyanobacteria, such as the abundance and biomass, were minimal in spring and maximal in the summer–autumn period. In each of the seasons of the year studied, toxic and potentially toxic species belonging to the genera Anabaena, Aphanizomenon, Lyngbya, Microcystis, Nodularia, and Nostoc were present among the detected cyanobacteria. The total contribution of the representatives of these genera to the total abundance of phytoplankton changed from 4.0% in spring to 65.0% in autumn. In summer, the portion of cyanobacteria from the above genera in the total abundance of microalgae accounted for about 40.0%. The largest role was noted for the algae Microcystis aeruginosa (Kützing) Kützing, which causes "blooming" of the reservoirs and produces a microcystin toxin with hepatotoxicity. The study of Pskov Lake requires constant monitoring of the content of cyanotoxins, especially in autumn, when the maximal biomass content of cyanobacteria (including toxic species) is observed, which can lead to serious consequences. [ABSTRACT FROM AUTHOR]

We have proposed compositions of titanyl hydrogen phosphate-based sorption materials modified with zirconium(IV) cations and containing both cation and anion exchange functional centers, represented by НРО and OH– groups, respectively. The synthesized materials were tested in sorption of antimony(III) cations and anions from high-salt solutions. Increasing the concentration of functional groups in ion exchange matrices has been shown to increase their affinity for antimony(III) ions. Such compositions can be regarded as promising ion exchange materials for efficient extraction of antimony radionuclides from multicomponent high-salt liquid radioactive waste. [ABSTRACT FROM AUTHOR]

Using a model solution, we have demonstrated the feasibility of using titanium(IV) oxyhydroxyphosphate-based ion-exchange materials for extraction of Cs+ and Sr2+ cations from multicomponent high-salt bottom residues. Conditions for the use of the ion exchangers have been optimized experimentally: liquid : solid = 50, t = 25°C. It has been shown that Cs+ is effectively extracted at pH 2, whereas Sr2+, at pH 8. The zirconium-modified sorbent has been shown to have a higher affinity for metal cations. The modified sorbent is especially selective for cesium in the acid pH region owing to the higher mobility of the protons of its hydrogen phosphate groups in comparison with the unmodified sorbent composition. [ABSTRACT FROM AUTHOR]

Abstract—A general characteristic of the river basin of the interstate Ural River and data on the economic use of the Ural River in its upper, middle, and lower reaches are given. Information on the hydrology of the liquid and solid flow of the Ural River is presented. Hydrochemical monitoring of the water bodies of the Ural River basin was performed during the flood period, the summer low-water period, and the autumn low-water period in the years 2017–2018. The hydrochemical monitoring of the water quality in the natural water bodies of the Ural catchment basin has revealed an excess in the MPC of heavy metal ions in the water of the studied water bodies for drinking water and for fishery water bodies. An excess in the MPC of cadmium ions for drinking water by 1.2–1.4 has been recorded in the Ilek River during low water periods, as well as in the Ural River near the border with the Russian Federation in the amount of 3.1–3.4 MPC for drinking water during the flood period and near the village of Zharsuat in the amount of 1.5–2.6 MPC for drinking water during summer and autumn low water periods. An excess in the MPC of lead ions for fishery water bodies by 1.2–1.4 has been revealed in the middle and lower reaches of the Ural River in different seasons of the year. Excessive concentrations of ions of different heavy metals compared to their MPC for fishery water bodies have been found in all water bodies in different periods of the year. The greatest excess of zinc ions compared to the MPC for fishery water bodies was observed during the low water period. [ABSTRACT FROM AUTHOR]

Abstract—One of the most promising methods of industrial wastewater treatment is flocculation using polyacrylamides. The purpose of our research was to estimate the efficiency of the use of new types of polyacrylamide-based flocculants for industrial wastewater treatment. The objects of the study were wastewaters from the Saratov Chemical Plant of Acrylic Polymers Akripol, as well as several flocculants (water-soluble polymers) based on acrylamide, acrylic acid, and chitosan. It has been established that the optimal dose of H600TM nonionic flocculant was 5 mg/dm3. The efficiency of industrial wastewater treatment was studied on two samples of weakly cationic flocculants (215-2 and 233-2) synthesized in a laboratory way, as well as on a sample of nonionic H600TM flocculant. It has been revealed that the tested flocculants do not significantly influence the pH value and content of sulfate ions in water. Flocculant 233-2 with the highest chitosan content was the best in terms of chemical oxygen demand, dry residue, and the amount of suspended solids. Flocculant 215-2 with the lowest chitosan content had a slightly worse performance. The worst of the tested flocculants was the nonionic H600TM, which does not contain chitosan. [ABSTRACT FROM AUTHOR]

Abstract—The status of the photosynthetic pigments in the aquatic plants Lemna minor L. and Elodea canadensis Michx. under the action of Ni2+, Co2+, Cu2+ and Pb2+ acetates in concentrations of 5.00, 2.50, 1.25, 0.62, 0.31, 0.15, 0.07, and 0.03 mg/L was assessed by changes in the fluorescence intensity of chlorophyll a and b and their ratio. It was established that nickel acetate in original solutions in all the above concentrations caused an increase in the fluorescence intensity of chlorophylls a and b in L. minor in relation to the control while the lead salt suppressed it. Co2+ acetate inhibited the fluorescence of chlorophyll a with concentrations in the initial solutions of 0.03 to 0.15 and 2.50 mg/L and that of chlorophyll b at all concentrations, except 0.62, 1.25, and 2.50 mg/L. For E. canadensis, it was found that the salts of all metals at all concentrations caused a reduction of the fluorescence intensity of chlorophyll a relative to the control and increased it in the case of chlorophyll b. The exception was the effect of copper and lead acetates with a concentration of 1.25 mg/L, when the fluorescence intensity of chlorophyll b was maintained at the control level. The presence of Ni2+, Co2+, Cu2+, and Pb2+ acetates in all concentrations in the culture medium influenced the quantitative and qualitative characteristics of chlorophyll a and b, which indicated a violation of the photosynthesis process. Our data on the change in the chlorophyll a/b ratio led to a conclusion about degradation of chlorophyll a relative to chlorophyll b after the effect of heavy metals. [ABSTRACT FROM AUTHOR]

The effect of cationic and anionic impurities on the varistor properties of high-voltage ZnO ceramics with a ZnO content of 75 wt % and a weight ratio of oxides of alloying elements Bi2O3:Sb2O3:Al2O3:Co3O4:NiO = 1.00 : 0.45 : 0.80 : 0.65 : 0.53 has been studied. It was found that anionic Cl–, F–, SO42–, PO43– and cationic Li+, Na+, K+, Cs+ and Mg2+ impurities worsen, while cationic impurities Ca2+, Sr2+, Ba2+ significantly improve the properties of ceramics. With the introduction of 0.3 wt % BaO, ZnO-75 ceramics, promising for the production of high-voltage varistors, were obtained. [ABSTRACT FROM AUTHOR]

The influence of the type of the matrix on the process of sorption concentration of pyrene (one of the best-known ecotoxicants of the series of polycyclic aromatic hydrocarbons (PAHs)) in homogeneous and heterogeneous solutions (distilled water, an R-12 solvent (a mixture of toluene, butyl acetate, and xylene), and an aqueous micellar solution of an anionic surface-active substance, sodium dodecyl sulfate) as well as on its further determination via solid-phase luminescence is studied. The sorption properties of the following matrices are compared: a cellulose sorbent (filter paper) and filter materials based on polypropylene, viscose, and polyester. It is found experimentally that, upon studying solutions of pyrene in water and an R-12 solvent for sorption and further recording of solid-phase luminescence, a hydrophobic polypropylene matrix is more suitable; however, in the case of the use of aqueous micellar solutions of sodium dodecyl sulfate, it is preferable to execute the sorption and observe the solid-phase luminescence of pyrene on a viscose matrix. The obtained results can be used for developing a highly sensitive method for the monitoring of the concentration of pyrene in various environments. [ABSTRACT FROM AUTHOR]

The effect of targeted, glycerol-aided modification of natural clay mineral bentonite was studied in terms of changes in the structure and general properties of the adsorbent material. The modification was performed using natural bentonite with a high content of montmorillonite. The bentonite micro- and mesoporosity can be increased by introducing certain struts—pillars into the interlayer structure of aluminosilicates. The data on structural features and physicochemical properties of granular formed samples of adsorbents based on the original bentonite clay were compared to those of glycerol-modified ones. Specific surface area, porosity, volume, and pore size distribution values of the samples studied were measured using the sorption method and gas capillary condensation techniques. The structure of the samples was determined was determined with X-ray phase analysis, and their elemental composition was found with an energy dispersive spectrometer. It was proved that bentonite was modified by pyrolytic carbon resulting from decomposition of glycerol in an oxygen-free medium, in the course of annealing of pellets. The modified bentonite adsorbent had a 4-fold higher specific surface area value compared to the starting material with retention of the basic elemental composition. [ABSTRACT FROM AUTHOR]

Studies were carried out to reduce the leakage current of high-voltage ZnO varistor ceramics by varying Sb2O3 and NiO content in a ZnO-Bi2O3-Sb2O3-Al2O3-Co3O4-NiO. It was found that the ceramic composition (wt %): ZnO 80, Bi2O3 5.83, Sb2O3 2.62, A12O3 4.66, Co2O3 3.80, NiO 3.09, has a minimum leakage current density Iout ≤ 0.1 μA cm-2, breakdown voltage Ub = 4.1kV mm-1, nonlinearity coefficient α = 65. The resulting ceramics are promising for the production of varistors with high stability of performance. [ABSTRACT FROM AUTHOR]

This paper presents a study aimed at determining the weight ratio of oxide additives for obtaining high-voltage ceramics in the ZnO–Bi2O3–Sb2O3–Al2O3–Co3O4 system containing 90 wt % ZnO, with a leakage current density under 1 μA/cm2. The ceramic containing the oxide additives in the ratio Bi2O3 : Sb2O3 : Al2O3 : Co3O4 = 0.25 : 0.17 : 1.4 : 1.4 has a nonlinearity coefficient as high as α = 69, a leakage current density as low as Il = 0.4 μA/cm2, and a breakdown voltage Vb = 4.1 kV/mm. [ABSTRACT FROM AUTHOR]

This paper presents a study aimed at determining the weight ratio of oxide additives for obtaining high-voltage ceramics in the ZnO–Bi2O3–Sb2O3–Al2O3–Co3O4 system containing 90 wt % ZnO, with a leakage current density under 1 μA/cm2. The ceramic containing the oxide additives in the ratio Bi2O3 : Sb2O3 : Al2O3 : Co3O4 = 0.25 : 0.17 : 1.4 : 1.4 has a nonlinearity coefficient as high as α = 69, a leakage current density as low as Il = 0.4 μA/cm2, and a breakdown voltage Vb = 4.1 kV/mm. [ABSTRACT FROM AUTHOR]

Abstract: The methods of thermal cyclic tests used for determining the thermal fatigue resistance of materials are analyzed using thermal cyclic maps (TC maps). These methods are based on the construction of the dependence of life time N on plastic strain in a cycle εp. An analysis showed that the dependence of N on εp does not give complete information on the thermal fatigue of materials, since it is built without consideration of the peculiarities of developing deformation related to their physicomechanical properties during a thermal cycle of tests. This is observed, for example, in the studies of single-crystal turbine blade materials, in which many conflicting data are obtained according to the results of testing VKNA-1V and ZhC6F alloys. [ABSTRACT FROM AUTHOR]

For planning of thermal fatigue tests of materials and comprehensive analysis of their results, it is proposed to use the thermal cyclic test maps (TC-maps) that allow tracing the strain development in a thermal cycle. TC-maps illustrate the diagrams of the temperature-dependent elastic strain, which corresponds to the yield strength of the material, and the free strain variation under constraint conditions. This paper presents the procedure of thermal cycle test map compiling for some materials and their physical as well as mechanical properties. The useful information obtained from the TC-maps is exemplified by some heat-resistant alloys employed for the production of gas-turbine engine blades. [ABSTRACT FROM AUTHOR]

This paper examines the influence of the location of settlements, railroads, and highways on the spatial structure of the Otis tarda population in the Trans-Volga region that was studied in the years 1998-2016 in a model area of 12000 km2 that is located in the southern part of the Saratov Trans-Volga region. The zone of the impact made by our estimated disturbance factor due to the movement of people and a variety of ground vehicles along various-purpose roads on the territorial distribution of bustards in autumn can be denoted as a 300-500 m width band on both sides of the transport communications. Shelterbelts that were created along transport communications render a beneficial effect on the distribution of O. tarda and reduce the influence of the disturbance factor. Furthermore, crop rotation fields with side sizes of more than 1 km can be considered a factor that compensates for the anxiety of birds. We have found that in the Saratov Trans-Volga region, because of the large size of crop rotation fields and significant development of roadside and shelter belts, no special measures are required to protect O. tarda such as restrictions on the movement of people and vehicles over the territory where this species lives. [ABSTRACT FROM AUTHOR]

The ion-plasma thermal barrier coatings deposited onto samples and blades made of intermetallic VKNA-1V and VKNA-25 alloys are tested in a laboratory. The external ceramic layer of the thermal barrier coatings (TBC) is formed by magnetron sputtering of zirconium alloy targets and has a columnar structure. The influence of NiCrAlY(Re, Ta, Hf) + AlNiY(Hf) + ZrYGdO TBC on the long-term strength at a test temperature of 1200°C and on the high-cycle fatigue at a temperature of 900°C is studied. Blades with TBC are subjected to thermal cycling tests in the temperature range 950 ↔ 400°C and 1050 ↔ 400°C during air cooling and in the range 950 ↔ 200°C during water cooling at 500 cycles. The temperature fields in the cross section of a blade airfoil during thermal cycling are calculated. The laws of formation of fracture zones and the development of thermal fatigue cracks under the conditions that are close to the operating conditions of nozzle TBC-containing blades are investigated. [ABSTRACT FROM AUTHOR]

Under conditions of Klimov engineering enterprise, industrial results are obtained for the first time for developing casting technology for small single-crystal uncooled GTE turbine rotor blades of a new heatresistant alloy VZhM7 with reduced density and with a crystal orientation of <001>. Structural models are developed for blocks of blades with seeds and heat-resistant alloy melting and pouring in a unit for directional solidification. Test batches of blade castings are obtained with a yield of finished single-crystal structure of not less than 90% under VIAM pilot plant conditions, and 80% under conditions of Klimov engineering enterprise. The structure and phase properties are given for single-crystal blade material after casting, hot isostatic pressing, and subsequent heat treatment. Data are provided for fatigue tests on blades with crystal orientation <001>. [ABSTRACT FROM AUTHOR]

The structure and properties of carbon-containing single-crystal alloy ZhS32 and carbonless single-crystal alloys ZhS36, VZhM4 and VZhM5U are studied after 500 - 3000-h aging at 850 - 1100°C. The resistance to elastoplastic strain, creep and fatigue and the characteristics of long-term strength of the alloys are determined. It is shown that the expected values of long-term strength and creep resistance of the single-crystal alloys should be corrected with allowance for the changes in their initial structure after long-term operation. [ABSTRACT FROM AUTHOR]

This paper presents a study aimed at optimizing the composition and sintering conditions of highvoltage ZnO varistor ceramics. We demonstrate that, with allowance for the cost of starting materials, the optimal composition of high-voltage ZnO varistor ceramics is as follows (wt %): ZnO, 90; BiO, 2.76; SbO, 1.92; AlO, 3.32; and CoO, 2. The optimal sintering conditions are isothermal holding at a temperature of 975°C for 2 h. The ceramics thus prepared have V = 4.5 kV/mm, α = 50, I = 1.1 μA/cm, density ρ = 5.67 g/cm (relative density of 96.1%). [ABSTRACT FROM AUTHOR]

Results of experimental studies of creep in a wide range of temperatures and stresses are presented for three modern single-crystal nickel-base alloys. A method for determining the creep characteristics by tests including step increase of the tension is suggested and tested. The effect of transition into plastic condition on the creep parameters, the influence of the chemical composition and loading conditions on the duration of creep stages I, II and III, and the conditions of appearance of crystallographic and not crystallographic modes of fracture are analyzed. Possible simple approximations of the creep curves are considered with allowance for the accumulation of damage and occurrence of unsteady creep stages. [ABSTRACT FROM AUTHOR]

We have examined the effect of dopant concentration on the properties of ZnO varistor ceramics and determined the composition and conditions of the synthesis of ceramic powders and sintering of ceramics at a temperature of 925°C. We obtained a breakdown voltage of 2.8-3.0 kV/mm and nonlinearity coefficient in the range 48-55. [ABSTRACT FROM AUTHOR]

Using the materials from oceanographic observations for 1932-2014, the value of the 'new' primary production of the Sea of Okhotsk was assessed based on the loss of the silicon content in the euphotic layer. Average long-term estimates were performed for the spring-summer period (May-July) after 'cold' and 'warm' hydrological winters. It is shown that in the main part of the surveyed area, the spring-summer phytoplankton production was 1.5-2.0 times higher after warm winters than after cold winters. [ABSTRACT FROM AUTHOR]

Varistor powders were synthesized by accelerated combustion of an aqueous solution of hydrated zinc, bismuth, aluminum, cobalt, and nickel nitrates, antimony tartrate, and sugar at 500°С with isothermal heating for 10 min, followed by grinding and calcination at 700°С for 1 h. The varistor powders obtained have high specific surface area and allow preparation of a ceramic with high values of the breakdown voltage and nonlinearity coefficients and with low leakage current density. The ceramic of the optimum composition (wt %), ZnO 75, BiO 7.36, SbO 5.1, AlO 7.19, CoO 4.8, and NiO 0.61, sintered at 975°С for 4 h, has U = 4.2 kB mm, α = 54, and I = 0.2 μA cm. [ABSTRACT FROM AUTHOR]

The dynamics of microbial biofilm formation by standard strain and by clinical strains of uropathogenic coliform bacteria was investigated in vitro and the effect of sublethal concentrations of the polymer compound polyazolidinammonium modified with iodine hydrate ions on the initial stages of biofilm formation was assessed. Treatment of immunological plate wells with the polymeric compound prevented film formation, especially in case of clinical E. coli strain carrying FimH virulence gene. [ABSTRACT FROM AUTHOR]

It was found in using anatase titanium oxide for the preparation litium hexafluorotitanate by interaction of titanium hydroxide or oxide and lithium fluoride with hydrofluoric acid an output of LiTiF reached 97.1% at 'reverse' synthesis, 100% consumption of LiF and 200% consumption of 54% HF. [ABSTRACT FROM AUTHOR]

Synthesis of MgAlO from a stoichiometric mixture of aluminum and magnesium nitrates by its burning with urea, glycine, sugar, and mixtures of these as a fuel was studied. [ABSTRACT FROM AUTHOR]

Three ways to synthesize MgA1O precursor were studied with use of a two-step precipitation at the beginning of ions Mg and then Al with ammonium hydroxide, ammonium carbonate, and mixture thereof. Efficiency of these ways was evaluated with the aid of a residual amount of cations Mg and Al in the mother liquor. [ABSTRACT FROM AUTHOR]

The reaction between Nb2O5 and NH4HF2 is studied by thermogravimetric analysis, IR spectroscopy, and crystal-optical analysis. Intermediates and their formation temperatures are determined. [ABSTRACT FROM AUTHOR]

The phagocytic activity and production of proinflammatory cytokines by murine peritoneal macrophages was examined upon in vitro and in vivo exposure to low doses (up to 150 mJ/cm2) of red (650 nm) and infrared (850 nm) light generated by semiconductor lasers. Infrared irradiation proved stimulatory in a dose-dependent way for phagocytosis and killing of enteropathogenic Escherichia coli as well as for cytokine production. Red light markedly enhanced cytokine production but was detrimental to macrophage activity and at higher doses caused their destruction. [ABSTRACT FROM AUTHOR]

Thermal gravimetric, X-ray phase, IR spectroscopic, and chemical analyses were applied to study the reaction of yttrium and neodymium oxides with NHHF. [ABSTRACT FROM AUTHOR]