National Taras Shevchenko University of Kyiv
Recent publications
The article examines the current state tax system’s impact on the ability to finance investment costs of the enterprise. In unstable market environment conditions of domestic enterprises’ financial management system, the investment activity intensification problem for the purpose of their sustainable development and competitive position strengthening maintenance is actual. The insufficient level of modern enterprises’ investment activity is due to limited investment resources. One of the important factors influencing this process is the current taxation system. For businesses, taxes are part of the profits that can be invested in their own development. In these conditions, the objective is to form an investment management system that would provide the company with the opportunity for sustainable development, contribute to the growth of production, increase profitability, increase competitiveness in the market. The scientific work proposes enterprise investment costs financing sources planning model depending on the limit value of the tax burden integrated coefficient. The developed model is an important component of financial management, which determines the level of financial constraints on the opportunities for enterprise development. The comparison of the actual and the limit tax burden integrated coefficient values made it possible to determine the periods in which the enterprise’s tax burden did not limit the possibility of borrowing funds to finance investment activities.
The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of gravitational waves can be expected to provide key input. We provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. These connections must be developed for LISA to live up to its science potential in these areas.
Mechanical-biological treatment (MBT) is a popular solution for the processing of mixed municipal solid waste (MSW). However, it is assumed that the treatment processes can lead to the generation of microplastics in large quantities and their concentration in the organic output. Organic outputs from MBT as a source of microplastics are still poorly understood. The current article aims to fill this gap and investigate microplastics formation during MBT and their abundance in ready stabilized organic output. Seasonal samples were taken from the four stages of the possible microplastics pathway in MBT to study changes in microplastics numerical and mass concentration, shape and size. Large microplastics were identified by Fourier transform infrared spectroscopy, and small microplastics by Nile Red dye staining method. The results showed that both mechanical pre-treatment and aerobic treatment had a significant impact on microplastics formation, while mechanical post-treatment only resulted in the enrichment of the output with microplastics. Moreover, microplastics became finer during treatment. Microplastics abundance in ready organic output ranged from 8925 ± 1344 particles/kg in winter 2021 to 17407 ± 4319 particles/kg in summer 2020, and up to 160.5 t of microplastics were emitted from the Kaunas MBT treatment facility during the study year. In addition, a relationship between the microplastics abundance and plastic content of the incoming waste was found by a regression analysis. Therefore, to reduce the formation and emission of microplastics by MBT, the organic fraction of MSW should be collected and treated separately.
The paper develops an approach to the description of the evolution of correlations for many hard spheres based on a hierarchy of evolution equations for the cumulants of the probability distribution function governed by the Liouville equation. It is established that the constructed dynamics of correlations underlies the description of the evolution of the states of many hard spheres described by the BBGKY hierarchy for reduced distribution functions or the hierarchy of nonlinear evolution equations for reduced correlation functions. As an application of the developed approach to describing the evolution of the state of many hard spheres within the framework of dynamics of correlations, the challenges of the derivation of kinetic equations are discussed.
This paper is concerned with investigation of the structure and microwave properties of epoxy resin composites with graphite nanoplatelets (GNPs) decorated by FeNi nanoparticles prepared by the salt impregnation. It was confirmed by SEM and XRD that the method gives nanopowder where the metal componentFe20Ni80 is in the form of nanoparticles (20–40 nm in diameter) which are distributed over the surface and edges of the GNPs. The graphite phase in the investigated nanopowder is predominant, and Fe20Ni80 component mainly contains fcc FeNi3. Measurements of magnetic properties confirmed that Fe20Ni80 are small, randomly oriented assembly of spherical (or close to spherical) particles on the GNPs surface. The saturation magnetization of GNP-Fe20Ni80 particles is 25 emu/g and it weakly depends on temperature. Electrical resistivity measurements have shown that decoration of GNPs leads to essential increase of conductivities well as improvements EMR absorption properties in high frequency range (26–60 GHz) in (GNP-Fe20Ni80)/with in compression GNP/epoxy under the same volume content of 1.45 vol. % (GNP-Fe20Ni80)/L285 composites demonstrated superior broadband absorption properties with microwave absorption efficiency higher than 97 % in the whole investigated frequency region.The effective absorption bandwidths are as high as 12.2 GHz were observed at the frequency range 41.9 and 53.2 GHz and 13.3 GHz at the frequency range 51.1 GHz–64.4 for this composite. It is assumed that decoration of GNPs surface by nanoscale Fe20Ni80 particles leads to a formation of the multiple dielectric and magnetic loss mechanisms, such as interfacial polarization, dipole polarization, space-charge polarization, eddy current loss, Debye dipolar relaxation, natural resonance and exchange resonance, which improve the microwave absorption properties of the investigated composites.
A triple thermosensitive polymer Dextran-g-Poly(N-isopropylacrylamide)/Au nanoparticles/Perylenediimide (D-g-PNIPAM/AuNPs/PDI) hybrid nanosystem was formulated in aqueous solution for potential use as thermoresponsive fluorescent optical switch and label. The completely reversible effect of sharp enhancement-quenching of the photoluminescence of D-g-PNIPAM/AuNPs/PDI nanosystem was revealed during the heating-cooling cycle in the narrow temperature range of 25–47 °C, containing the temperature point of the LCST phase transition of the thermosensitive polymer. The sharp change in the intensity of photoluminescence was shown to result from the competing effects of plasmonic enhancement and non-radiative FRET transfer of electronic excitation energy during thermo-induced LCST transition of the D-g-PNIPAM macromolecule. The observed effect allows to carry out the temperature control of the photoluminescence intensity, which appears to be particularly important for potential applications of D-g-PNIPAM/AuNPs/PDI hybrid nanosystem in photonics, biology and medicine, such as thermosensitive fluorescent optical switch and label or intracellular fluorescent thermometer.
Functionalized 4,4‐difluorospiro[2.2]pentan‐1‐yl derivatives are proposed as promising building blocks for synthetic and medicinal chemistry. Scalable, efficient, and diastereoselective approach to their preparation via the difluorocyclopropanation of (2‐methylene­cyclopropyl)methanol is developed. Stability of the title scaffolds towards common reaction conditions is confirmed by a series of typical functional group transformations. Physicochemical characte­ristics (pKa, LogP, and aqueous solubility) and structural features of the key 4,4‐difluorospiro[2.2]pentan‐2‐yl derivatives are established and compared with those of non‐fluorinated analog, 2,2‐difluorinated isomer, as well as monocyclic gem‐difluorinated counterparts.
Propolis is a sticky resinous substance collected from buds, leaves, stems of wild plants and processed by bees, which has bactericidal properties and which they use to seal cracks in the hive, polish the walls of wax cells, embalm the enemy corpses. Currently, bee behaviour during the collection of propolis, its botanical origin and sources of production have been studied. The process of propolis accumulation in bee nests and the factors influencing the intensity and productivity of bee colonies need to be further studied, which will allow to control the propolis productivity of bees in the future. The purpose of this research was to investigate the ethology of honey bees during the accumulation of propolis in the nest and the collectors we have developed in order to find ways to increase propolis productivity and obtain commercial propolis. The research was conducted from June 28 till September 1, 2019, in an apiary in Baryshivka Raion of Kyiv Oblast, Ukraine. Bee colonies of the Ukrainian population were used. In the research we used designing, observation, zootechnical, microscopic and statistical methods. We concluded that honey bees dilute plant resin during the production and use of propolis in the nest. The consistency of diluted propolis can be different, which is due to the need to propolize different elements of the nest. The time, number of enzymes required for such dilution, and the physicochemical properties of the resin may affect the propolis productivity of bee colonies. This requires further research. Visual estimation of the propolis amount in the constructed collectors suggests that the collectors do not provide significant amounts of propolis. At the same time, the propolis placed in the meshes visually did not contain wax, which indicates its high quality and requires additional research into the development of this technology. For the first time, it has been established that during the manipulation of propolis, honey bees can lose parts of it due to its dilution by enzymes of the mandibular glands.
The emergence of new players – fintech companies, neobanks and non-banking companies – changes the structure of competition in the banking sector, reduces the profitability of traditional banking activities, and therefore forces banks to look for new sources of income. The paper deals with the issue of improving relations with clients in the banking sector of Ukraine, which is proposed to be implemented through the development of priority digital banking products and services. The study used a survey method using a statistical apparatus of a small unique sample, the degree of representativeness of which was assessed using the Student’s test. Slightly higher, closer to the level that characterizes the significant impact on the client’s perception of the whole complex of digital activities in the case of Polish banks (3.81, with a maximum possible score of 5.0) than Ukrainian banks (3.75), which indicates greater involvement and willingness to accept the digitalization of the people of Poland. Generally, banks in both countries are recommended to use a customer-oriented approach in forming product policy using digital products and services, which should be implemented and developed in practice in specific areas identified during customer surveys.
The aim of the article: The aim of this article was to identify the humanitarian features of the use of media technologies in education. To achieve this goal, a analytical research was conducted onthe topic of media in education. Research methods and techniques: The historical and comparative-legal method was used to solve the issue. Using a comparative legal method, a comparative analysis of the level of using media in education was carried out. Results: As a result, conclusions were made about the sharp increase in the level of use of media in various types in the process of civic education.Conclusions: It was concluded that media have both positive and negative effects on consciousness of information. Active use of media technologies helps to recreate the learning process at a distance, involves the use of a variety of interactive activities. And, the constant use has a burden than the usual format of education. Therefore, the problem of teaching methodology of using media in education becomes relevant. As a result, it was determined that the topic of effective use of media technologies in the educational process is becoming increasingly important.
The article deals with the influence of globalization on the educational and scientific processes. The tendencies of education in globalization are determined. The peculiarities of globalization of education are considered. The article investigates the main aspects of the educational and scientific prospects of the XXI century. XXI century -this is the time of transition to a high-tech information society, in which the quality of human potential, the level of education, and culture of the entire population acquires a decisive value for the country's economic and social progress. Integration and globalization of social, economic and cultural processes that are taking place in the world, prospects for the development of the Ukrainian state for the next two decades require a deep update of the education system, leads to its advanced character. The main tendencies in the modernization of education are recognized: democratization of the entire system of training and education; increase in the fundamentality of education; Humanization and humanitarianization of education, use of the latest technologies of training; Integration of various forms and education systems both at the national and world levels.
In 2014–2015 and 2019–2021, teleost fishes off Galindez Island (Antarctic Peninsula) were examined for trematodes. Combined morphological and molecular analyses revealed the presence of eight trematode species of four families (Hemiuridae, Lecithasteridae, Opecoelidae, Lepidapedidae) from five fish species. Only adult trematodes were found and all of them are Antarctic endemics with their congeners occurring on other continents. The hemiuroids, Elytrophalloides oatesi (Leiper & Atkinson, 1914), Genolinea bowersi (Leiper & Atkinson, 1914), and Lecithaster macrocotyle Szidat & Graefe, 1967 belong to the most common Antarctic species and together with Lepidapedon garrardi (Leiper & Atkinson, 1914) and Neolebouria georgiensis Gibson, 1976 they were recorded as the least host-specific parasites. The originally sub-Antarctic Neolepidapedon macquariensis Zdzitowiecki, 1993 is a new record for the Antarctic Peninsula and Parachaenichthys charcoti (Vaillant), is a new host record. Neolebouria terranovaensis Zdzitowiecki, Pisano & Vacchi, 1993 is considered a synonym of N. georgiensis because of identical morphology and dimensions. The currently known phylogenetic relationships within the studied families are supported, including the polyphyly of Macvicaria Gibson & Bray, 1982 with the future need to accommodate its Antarctic species in a new genus. The validity of M. georgiana (Kovaleva & Gaevskaja, 1974) and M. magellanica Laskowski, Jezewski & Zdzitowiecki, 2013 needs to be confirmed by further analyses. Genetic sequence data are still scarce from Antarctica, and more studies applying integrative taxonomic approaches and large-scale parasitological examinations of benthic invertebrates are needed to match sequences of larval stages to those of well-characterised adults and to elucidate trematode life-cycles.
We prove limit theorems for the greatest common divisor and the least common multiple of random integers. While the case of integers uniformly distributed on a hypercube with growing size is classical, we look at the uniform distribution on sublevel sets of multivariate symmetric polynomials, which we call hyperbolic regions. Along the way of deriving our main results, we obtain some asymptotic estimates for the number of integer points in these hyperbolic domains, when their size goes to infinity.
Background: University students are a high-risk group for stress, consumption of junk food and significant weight gain over a short period. Inadequate vitamin D intake has been linked to many health issues, including chronic headache, apathy, aggression and depression. Furthermore, vitamin D deficiency led to dysbiosis of the gut microbiota. The purpose of our study was to estimate the effect of 90-days healthy lifestyle programs along with gut microbiota modulation in university students with vitamin D 3 deficiency. Methods: In this randomized controlled trial, 130 students (18-25 years old) with vitamin D deficiency were recruited. Both the standard care group (N.=65) and the intervention group (N.=65) received a 3-months course of individually selected nutrition program and physical activity (8000-10,000 steps daily). The intervention group received an additional treatment with synbiotic Acidolac and vitamin D 3 for 3 months. The psycho-emotional status of the participants was assessed by a validated questionnaire that examined situational anxiety. In all students, blood pressure, anthropometric variables, as well as laboratory metabolic parameters, were recorded. Results: In both groups, vitamin D 3 deficiency was associated with instability and lability of mental processes, mood swings, bad sleep, high rates of stuck and agitation for any problem. Combined therapy (diet, physical activity and synbiotic) induced a significant improvement in the psycho-emotional state of students. The 90-days therapy vitamin D 3 increased the level of vitamin D 3 in serum in the intervention group. Lastly, we observed a decrease in the body weight, body mass index, waist circumference and fatty mass, only in students included in the interventional group. Conclusions: Nutrition program, physical activity, vitamin D 3 intake and gut microbiota modulation led to both the improvement in vitamin D levels in serum and emotional harmonization.
The formation of GeSn nanostructures catalyzed by Sn surface droplets during the growth of Ge1-xSnx/Ge/Si(001) heterostructures provide a promising strategy for the growth of high-quality Sn-containing group-IV alloys. The droplet formation is favored by Sn segregation at dislocation cores and diffusion of Sn towards the sample surface. Subsequent Sn droplet motion along <110> crystallographic directions result in self-assembled Ge stripes along the droplet’s path. A novel phenomenon is observed, for which Sn-rich GeSn nanowires (NWs) were periodically formed on top of Ge(Sn) stripes. While the front edge of the liquid Sn droplet is continuously moving and dissolving the Ge1-xSnx epilayer, the phenomenon of NW periodicity is explained by discrete jumping of the back edge of the droplet resulting in redeposition of material forming the NWs. It is also demonstrated that Sn-induced phase separation of metastable Ge1-xSnx epilayers leads to carrier redistribution and an electric-field-induced conductivity type conversion from p- to n-type in the Ge(Sn) stripes. These results advance our understanding of the Sn segregation and phase separation mechanism for Ge1-xSnx epilayers at relatively low temperature (≥ 230 °C). This study could pave the way for understanding the droplet epitaxy synthesis of Sn-rich GeSn nanostructures generating emergent functionalities of GeSn-based nanodevices.
Little is known about the mechanisms behind the bistability (memory) of molecular spin transition compounds over broad temperature ranges (>100 K). To address this point, we report on a new discrete FeII neutral complex [FeIIL2]0 (1) based on a novel asymmetric tridentate ligand 2-(5-(3-methoxy-4H-1,2,4-triazol-3-yl)-6-(1H-pyrazol-1-yl))pyridine (L). Due to the asymmetric cone-shaped form, in the lattice, the formed complex molecules stack into a one-dimensional (1D) supramolecular chain. In the case of the rectangular supramolecular arrangement of chains in methanolates 1-A and 1-B (both orthorhombic, Pbcn) differing, respectively, by bent and extended spatial conformations of the 3-methoxy groups (3MeO), a moderate cooperativity is observed. In contrast, the hexagonal-like arrangement of supramolecular chains in polymorph 1-C (monoclinic, P21/c) results in steric coupling of the transforming complex species with the peripheral flipping 3MeO group. The group acts as a supramolecular latch, locking the huge geometric distortion of complex 1 and in turn the trigonal distortion of the central FeII ion in the high-spin state, thereby keeping it from the transition to the low-spin state over a large thermal range. Analysis of the crystal packing of 1-C reveals significantly changing patterns of close intermolecular interactions on going between the phases substantiated by the energy framework analysis. The detected supramolecular mechanism leads to a record-setting robust 105 K wide hysteresis spanning the room temperature region and an atypically large TLIESST relaxation value of 104 K of the photoexcited high-spin state. This work highlights a viable pathway toward a new generation of cleverly designed molecular memory materials.
The Russian invasion of Ukraine is negatively affecting the development of the Ukrainian academy, now and in the foreseeable future. Different academic stakeholders around the world have reacted differently to this war, some imposing sanctions against Russia and/or providing aid to Ukraine. Some scientific publishers have partially or temporarily suspended sales and marketing of products and services to research organizations in Russia and Belarus. The issue of banning publication in international journals by authors from Russian institutions remains controversial and needs to be carefully considered by various stakeholders.
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3,354 members
Ivan Ogorodnyk
  • Faculty of Chemistry
Mikhail Moklyachuk
  • Faculty of Mechanics and Mathematics
Nataliіa Lyzhachenko
  • Faculty of Geology
Alexander Alexandrov
  • Astronomical Observatory
Sergii Tukaiev
  • Institute of Biology and Medicine, Institute of Journalism
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64/13 Volodymyrska St., 01601, Kyiv, Ukraine
Head of institution
Leonid V. Hubersky
Website
http://www.univ.kiev.ua/