Михайло Павлович Моклячук – до 75-рiччя вiд дня народження

On September 28, 2023, Mykhailo Moklyachuk, Doctor of Physical and Mathematical Sciences, Professor, Laureate of the State Prize of Ukraine in Education, Honored Worker of Science and Technology of Ukraine, and Academician of the Academy of Sciences of the Higher School of Ukraine, celebrated his 75th birthday. His scientific research is devoted to the study of stationary random processes, functionalities of stationary processes, and random fields. Pages of the article in the issue: 13 - 15 Language of the article: English28 вересня 2023 року виповнилося 75 років від дня народження Моклячука Михайла Павловича, доктора фізико-математичних наук, професора, лауреата Державної премії України в галузі освіти, заслуженого діяча науки і техніки України, академіка Академії наук вищої школи України. Наукові дослідження Михайла Павловича присвячені дослідженню стаціонарних випадкових процесів, функціоналів від стаціонарних процесів та випадкових полів

Synthesis and examination of nanocomposites based on poly(2-hydroxyethyl methacrylate) for medicinal use

Preparation of poly(2-hydroxyethyl methacrylate) (PHEMA) based nanocomposites using different approaches such as synthesis with water as the porogen, filling of polymer matrix by silica and formation of interpenetrating polymer networks with polyurethane was demonstrated. Incorporation of various biologically active compounds (BAC) such as metronidazole, decamethoxin, zinc sulphate, silver nitrate or amino acids glycine and tryptophan into nanocomposites was achieved. BAC were introduced into the polymer matrix either (1) directly, or (2) with a solution of colloidal silica, or (3) through immobilization on silica (sol-densil). Morphology of prepared materials was investigated by laser scanning microscopy and low-vacuum scanning electron microscopy. In vacuum freeze-drying, prior imaging was proposed for improving visualization of the porous structure of composites. The interaction between PHEMA matrix and silica filler was investigated by IR spectroscopy. Adsorption of 2-hydroxyethyl methacrylate and BAC from aqueous solution on the silica surface was also examined. Phase composition and thermal stability of composites were studied by the differential thermogravimetry/differential thermal analysis. Release of BAC into water medium from prepared composites were shown to depend on the synthetic method and differed significantly. Obtained PHEMA-base materials which are characterized by controlled release of BAC have a strong potential for application in manufacturing of different surgical devices like implants, catheters and drainages. © 2017, The Author(s)

Co–Fe–oxide nanoparticles supported on the various highly dispersed matrices: the effect of the carrier on structural and magnetic properties

A series of mixed oxides was synthesized by deposition of the guest phase on the highly dispersed oxide matrix. Fumed nanooxides SiO2, Al2O3, SiO2/Al2O3, and SiO2/Al2O3/TiO2 with the specific surface area of 65–91 m2/g were selected as highly dispersed matrices. Co–Fe mixed oxides with the general formula Co4xFexOy (Co: Fe = 4: 1) were deposited as the guest oxides using the two-step method: (i) solvate-stimulated modification of the surface of fumed nanocarriers with the mixture of cobalt nitrate (II) and iron (III) formate and (ii) subsequent heat treatment up to 600 °C to form Co4xFexOy. The aim of this paper was to study the influence of the composition and structure of fumed oxide matrices and deposited guest phase on the morphology of the resulting composites in the gaseous and aqueous media using the XRD, XPS, FTIR, nitrogen adsorption and SEM/EDX, as well as quasi-elastic light scattering (QELS) methods. The low-temperature nitrogen adsorption isotherms have a sigmoidal shape with a narrow hysteresis loop characteristic of mesoporous materials. The specific surface area (SBET) of the composites varies from 48 to 82 m2/g, showing a tendency towards a decrease in the SBET values by 10–26% in comparison with the initial nanocarriers. The SEM data show the denser aggregate structure of nanocomposites compared to the initial carriers. The primary particle size was in the 30–60 nm range and the EDX data confirm the formation of a guest phase on the mixed aluminosilicate carriers, mainly in the surface patches corresponding to the alumina structure. According to the QELS data, there is a tendency to form aggregates of 100–10 μm in size in the aqueous media. The XRD method shows that the deposited metal oxides are in the form of crystalline phases of Co3O4 with the crystallites of 25–26 nm in size for the individual SiO2 and Al2O3 nanocarriers and 34–37 for the mixed ones, but the iron oxide reflections were not identified for the composites. XPS observation demonstrates the signal of Fe 2p electrons as the form of Fe2O3 oxide in the surface layer of nanocomposites as well as Co 2p as the Co3O4 and Co(OH)2

КОНТАКТНА ВЗАЄМОДІЯ СКЛАДНОПРОФІЛЬНИХ ДЕТАЛЕЙ З УРАХУВАННЯМ ЛОКАЛЬНОЇ ПОДАТЛИВОСТІ ПОВЕРХНЕВОГО ШАРУ

In the present work the contact problem is solved for complex-shaped elements of engineering structures with local compliance of the surface layer. For this purpose a variation to the boundary integral equations method extended with a Winkler-type model of elastic layer is proposed. The resulting approach combines in a unified formulation the "local" and "global" compliance characteristics of the contacting rough bodies. The numerical implementation of the boundary element method is included in a software-and-model complex for analysis of contact interaction of complex-shaped bodies. A number of applied contact problems is solved. Namely, the influence of the gap and rough layer compliance on the contact pressure distribution is studied for the following cases: contact of a rectangular round-end stamp with a flat surface, junction of a rolling bearing and a modified double-radius roller, normal traction between spherical pistons and treadmills of a tank transmission. Numerical results of the research are compared to experimental data. Accuracy and reliability of the proposed methods and models, as well as special-purpose software-and-model complex are confirmedВ работе решена задача анализа контактного взаимодействия сложнопрофильных элементов машиностроительных конструкций при наличии локальной податливости поверхностного слоя. Для этого предложен вариант метода граничных уравнений, в который добавлена модель упругого промежуточного слоя Винклера. Полученный метод исследования контактного взаимодействия объединяет в рамках единых соотношений "локальные" и "глобальные" характеристики податливости контактирующих шероховатых тел. Численная реализация метода граничных элементов осуществлена в специализированном программно-модельном комплексе для исследования контактного взаимодействия сложнопрофильных тел. Решен ряд прикладных задач анализа контактного взаимодействия, а именно проведено исследование влияния формы зазора и податливости шероховатого слоя на характер распределений контактных давлений для следующих случаев: контакт прямоугольного в плане штампа со скруглениями с плоскостью, сопряжение подшипника качения с модифицированным двухрадиусным роликом, передача усилий между шаровыми поршнями и беговыми дорожками в гидрообъемной передачи танковой трансмиссии. Проведено сравнение полученных численных результатов исследований с экспериментальными данными. Подтверждена точность и достоверность предложенных методов и моделей, а также созданного программно-модельного комплексаСтаття  присвячена розробці підходів, методів і моделей для дослідження напружено-деформованого стану складнопрофільних тіл з урахуванням їхнього контакту по шорстких поверхнях. У роботі розв'язана задача аналізу контактної взаємодії складнопрофільних елементів машинобудівних конструкцій за наявності локальної податливості поверхневого шару. Для цього запропоновано варіант методу граничних рівнянь, в який додана модель пружного проміжного шару за Вінклером. Числова реалізація методу граничних елементів здійснена в спеціалізованому програмно-модельному комплексі. Розв'язано низку прикладних задач аналізу контактної взаємодії, а саме проведено дослідження впливу форми зазору і податливості шорсткого шару на характер розподілів контактного тиску у наступних випадках: контакт прямокутного в плані штампа з округленнями з плоскою поверхнею, спряження підшипника кочення з модифікованим дворадіусним роликом, передача зусиль між  кульовими поршнями та біговими доріжками в гідрооб'ємній передачі танкової трансмісії. Проведене порівняння отриманих числових результатів досліджень з експериментальними даними

Nanosized copper(ii) oxide/silica for catalytic generation of nitric oxide from S-nitrosothiols

Nitric oxide NO, mediates inflammatory and thrombotic processes and designing biomaterials capable of releasing NO in contact with biological tissues is considered to be a major factor aimed at improving their bio- and haemocompatibility and antibacterial properties. Their NO-releasing capacity however is limited by the amount of the NO-containing substance incorporated in the bulk or immobilised on the surface of a biomaterial. An alternative approach is based on the design of a material generating nitric oxide from endogenous NO bearing metabolites by their catalytic decomposition. It offers, at least in theory, an unlimited source of NO for as long as the material remains in contact with blood and the catalyst maintains its activity. In this paper we studied the catalytic properties of novel nanostructured CuO/SiO2 catalysts in generating NO by decomposition of S-nitrosoglutathione (GSNO) in vitro. CuO/SiO2 catalysts with different CuO loadings were synthesized by chemisorption of copper(II) acetylacetonate on fumed nanosilica followed by calcination. CuO content was controlled by a number of chemisorption–calcination cycles. Fourier-transform infrared spectroscopy and thermogravimetric analysis confirmed the formation of CuO/SiO2 nanoparticles (NPs) with particle size of CuO phase in the range from 71 to 88 nm. Scanning electron microscopy images revealed a uniform distribution of NPs without their sintering or agglomeration. All the materials of the CuO/SiO2 NP series exhibited NO-generating activity from GSNO confirmed by the Griess assay and by measuring the concentration of nitrite and nitrate anions in model solutions such as phosphate buffered saline and bovine serum. This activity is dependent on the material specific surface area and CuO exposure on the surface rather than CuO bulk content. The rate of NO production increased at higher initial concentration of the NO-bearing substrate studied in the range between 0.01 mM and 1.0 mM RSNO, which covers its physiological level. CuO/SiO2 NPs can be used to design polymers with NO generating properties at blood-biomaterial interface which are expected to have improved biocompatibility thus enhancing their potential for medical applications such as surgical tubing, peripheral venous catheters, auxiliary blood circulation devices and drug-eluting balloons

Physicochemical and Sorption Characteristics of Carbon Biochars Based on Lignin and Industrial Waste Magnetic Iron Dust

Magnetosensitive biochars were prepared with mechanochemical ball-milling of lignin and blast furnace dust with further pyrolysis at 800 °C under an inert gas atmosphere. The physicochemical and sorption characteristics of the materials were analyzed using several techniques: low-temperature nitrogen adsorption–desorption, X-ray powder diffraction, Raman spectroscopy, elemental analysis, potentiometric titration, and thermal analysis. All the synthesized biocarbons were characterized by their specific surface areas (SBET) in the range of 290–330 m2/g and microporous structures with certain contribution of mesopores in the total porosity. Equilibrium adsorption studies revealed the potential applicability of the materials in water remediation from hazardous organic substances modelled with methylene blue (MB) dye. Generally, this study illustrates the effective conversion of sustainable waste into a functional carbon material

Superhydrophobic MWCNTs/PDMS-nanocomposite materials: Preparation and characterization

The surface morphology, structure and hydrophobicity of low-and high-molecular weight poly(dimethylsiloxane) (PDMS) fluids physically adsorbed onto multi-walled carbon nanotubes (MWCNTs) at different weight percentages (5, 10, 20 and 40 wt.%), were studied employing X-ray diffraction (XRD), attenuated total reflectanceFouriertransforminfrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and measurements of contact angle with water. It was found that MWCNTs agglomerate forming voids between tubes of a broad range, while adsorption of the polymer from a hexane solution results in the expected wrapping of nanotubes withPDMS chains and, further, in filling voids, as represented by SEM data. ATR-FTIR was used to investigate the possible structural changes in the polymer nanocomposites. Based on the contact anglemeasurementsvia water drop shape analysis,MWCNTs/PDMS nanocomposites were characterizedas astable,superhydrophobic materials with the maximum contact angle (CA) equal to 152°at CPDMS=40wt.%