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Currently, it is necessary to assess competently and timely the technical condition of long-operated bridge crossings on the main canals of irrigation systems with increasing loads. The article considers structures with various defects and damages by the example of the Abinsky irrigation system of the Lower Kuban, examines the history of the issue of assessing the remaining resource of bridge structures. It includes the values of coefficients of significance of bridge crossing structures on the main canals of irrigation systems obtained by the authors based on the results of calculation. When designing irrigation systems, the estimated service life was no more than thirty years. Currently, on average, more than fifty years have already passed since the commissioning of the main irrigation systems, for example, in Krasnodar Territory. At the moment, the determination of the true value of the remaining resource is massively in demand not only in the construction field and hydraulic engineering, but also in many other branches of industrial production. For more effective control over the technical condition of bridge crossings on the main canals of irrigation systems, scientific and practical interest is primarily not only an understanding of the actual condition of the structure at the time of the survey, but also its alternative change, i.e. the forecast of its remaining resource. Assessment of the technical condition of the bridge crossing structures on the main canal is determining the possibility of their further long-term operation, the need for strengthening, reconstruction of bridge crossings on the main canals of irrigation systems.

The free expansion of a planar plasma surface is a fundamental non-equilibrium process relevant for various fields but as-yet experimentally still difficult to capture. The significance of the associated spatiotemporal plasma motion ranges from astrophysics and controlled fusion to laser machining, surface high-harmonic generation, plasma mirrors, and laser-driven particle acceleration. Here, we show that x-ray coherent diffractive imaging can surpass existing approaches and enables the quantitative real-time analysis of the sudden free expansion of laser-heated nanoplasmas. For laser-ionized SiO2 nanospheres, we resolve the formation of the emerging nearly self-similar plasma profile evolution and expose the so far inaccessible shell-wise expansion dynamics including the associated startup delay and rarefaction front velocity. Our results establish time-resolved diffractive imaging as an accurate quantitative diagnostic platform for tracing and characterizing plasma expansion and indicate the possibility to resolve various laser-driven processes including shock formation and wave-breaking phenomena with unprecedented resolution.

A typical food industry material (stainless steel) was laser-textured to evaluate biofouling of model surface relief. Both initial and laser-textured surfaces were characterized by scanning electron microscopy, energy-dispersive x-ray radiation, Raman spectroscopy, and scanning probe microscopy to reveal the most important pre-requisites for their biofouling by food pathogen bacteria.

Femtosecond low-energy Laguerre – Gaussian pulses of tightly focused visible laser radiation were employed for single-pulse ablative nanostructuring of a 50-nm thick gold film. Similar pulses of lower energy were employed for the efficient plasmonic photoluminescence excitation of a rhodamine 6G dye monolayer in the fabricated nanostructures. The consistency between the shape and polarisation symmetries of the low-energy laser beam, on the one hand, and the gold nanostructures produced by the same beam at a high radiation energy, on the other hand, opens the way to consistent nanostructuring and surface-enhanced analytical spectroscopy with the use of nanostructures.

The article considers the problem of STEM education in the context of improving the quality of science and mathematics literacy of pupils. The results of the monitoring study conducted by the “OsvitAnalityka” Analytical Center of Borys Grinchenko Kyiv University in cooperation with the Kyiv City Educational Agency and the Ukrainian Center for Educational Quality Assessment are presented. The state of formation of science and mathematical literacy of pupils as the ability to apply knowledge to solve practical problems for the implementation of STEM education has been established. Examples of practice-oriented integrated tasks in geography, chemistry, biology and physics that reveal the possibilities of STEM education are given. The success of the implementation of individual tasks, which involved subject integration and the use of knowledge in practice is analyzed. The most important factors influencing the quality of STEM education are highlighted: professional level of teachers, material and technical and educational-methodical support, motivation of pupils, practice-oriented content of education. As a result of the monitoring study, recommendations were prepared for general secondary education institutions for further implementation of STEM education.

Colloidal solutions of silver nanoparticles (NPs) were obtained by ultrashort-pulse laser ablation of silver films of variable thickness in water at different fluences, pulse durations and laser exposures. Characterization of these particles was performed by scanning electron microscopy, optical transmission spectroscopy, and dynamic light scattering. A monotonic increase in the extinction coefficient and in the average diameter of the colloidal particles—from 20 to 180 nm—was observed as a function of laser fluence and exposure. Antibacterial properties of colloidal silver NPs were investigated by the microbiological ‘Live/Dead Biofilm Viability Kit’ method.

The formation of alloyed Au/Pd nanoparticles (NPs) from thin magnetron-deposited Au–Pd films by nanosecond laser ablation in water is investigated. The films weight loss dependence is studied by thickness, intensity and laser pulses per point. Prepared NPs are transferred onto the silica wafer and characterized by scanning and transmission electron microscopy as well as optical and energy-dispersive x-ray spectroscopies. NPs size distribution was obtained using the dynamic light scattering (DLS) method.

The rapid development of society, increase in the population, land urbanization, growth of human economic activity contribute to the involvement in economic turnover of an increasing number of natural resources, the main part of which is water. Along with the depletion of water bodies, their pollution is also intensively occurring. The analysis of ecological state of basins of small rivers in the South of Russia shows a constant increase in the emission of pollutants into their channels. On the territory of Rostov region there are 5.572 rivers with a total length of 36.064 km. 90 % of rivers of Rostov region are less than 10 km long. On average, a local runoff in the amount of 3.36 billion m3 is formed on the territory of Rostov region per year. Increased anthropogenic activity leads to the disruption of functioning and stability of natural systems, which has a significant impact on small rivers, which are the most common elements of the hydrographic network. About 30 % of urban and about 90 % of rural population live in catchments of small rivers, while the greatest density is observed in the immediate vicinity of water banks. Small rivers significantly affect the hydrological, biological and biochemical regime of landscapes, maintaining the balance and redistribution of moisture and are important for water supply of the population.

The peculiarity of small rivers is the dependence of erosion-accumulative processes in their beds on the intensity of soil erosion in the catchment area: the smaller the river, the greater the contact with the catchment area of its channel, where mineral particles, washed off from its area, directly enter it. Soil erosion leads to the entry of an excessive amount of them into the channel of a small river, as a result of which sediment accumulation begins in it, siltation of the channel occurs. It leads to changes in the water regime of small rivers - a decrease in inter-soil runoff (up to the drying up of rivers), a sharp reduction in underground power supply. In the humid zone, due to the high water content, the siltation of small rivers is poorly expressed and has a local character. Siltation of small rivers is especially characteristic for the forest-steppe and steppe zones, as well as for the south of the forest zone. In the steppe zone of the European part of Russia, as a result of siltation, rivers of the first order completely disappeared, up to the fourth (up to 40-50 km long), leading to a total reduction of the river network by up to 30 %. In the forest zone, due to the disappearance of sources, the number of rivers of the first and second orders (up to 20 km long) decreased by 2.2 times. During the agricultural period (about 300 years), a layer of sediment with a thickness of 0.5 to 1 m accumulated in the beds and floodplains of small rivers in the southern half of the European part. The erosion of small riverbeds reaches on average only 20 % of washed off products, which is about 60 % of the total river sediment runoff. The rate of siltation of small rivers in the Don basin is 6-12 mm / year with a length of up to 25 km and about 1 mm/year with a length of 100 km and above. Siltation of small rivers is not typical for regions where the soil is washed away by meltwater, since the maximum flow of sediment into the rivers coincides with high water, when the channel-forming activity of water flows is most active.

According to modern standards, unique buildings and structures include buildings whose spans exceed 100 meters, with successful approbation in practical application, or spans over 60 meters with new design solutions, which require the development of new special calculation methods and the creation of physical models. Unique buildings include objects with a permanent number of people of more than 500, and periodic more than 1000-10,000 people, including people who are near the structure. The reliability of design solutions is confirmed by analyzing design schemes with subsequent assessment of methods and means of performing calculations. It is also necessary to observe, in order to study, the results of calculations for the strength and stability of the spatial system of a structure, to compare the data of theoretical materials with experimental ones obtained as a result of checks.

A comparison of single-pulse laser ablation of gold target by pulses with a 0.3–10 ps duration and a wavelength of 515 nm in air and in water was performed. The radiation was focused on the sample surface through the objectives with numerical apertures NA = 0.65 and 0.25. The influence of the medium, pulse duration, and spot size on the crater morphology was studied. A significant difference in crater morphology was found for different lenses. The ablation efficiency was studied by measuring the profiles of single-shot pulse craters using scanning force microscopy. The contribution of filamentation to the ablation process is shown quantitatively.