Using quantum chemical modelling, in this work, we considered the structure effects determining the adsorption of H and O atoms on (111), (100), (110) and (211) surfaces of gold, nickel and platinum nanoparticles. Surface deformation enhanced the adatom bonding to active sites with a large coordination number on flat (111) and (100) surfaces, while no distinct tendency was observed on kinked (110) and (211) surfaces. The effect of the neighboring atoms depends on the coupling matrix element $V_{ad}^2$. For metals with a considerable matrix element, the adsorption energy decreases with the rise in coordination number, and vice versa.

In this study, an enzyme-free electrochemical sensor based on zinc oxide (ZnO) nanorods synthesized by the thermal decomposition of zinc acetate is presented. The suggested approach ensures simplicity, environmental friendliness, and scalability of the process without the use of an autoclave or high pressure. The morphology and structure of the samples are studied using SEM, TEM, XRD, Raman, FTIR, XPS, PL, and UV-Vis spectroscopy. It is found that heat treatment at 450 °C increases the degree of crystallinity, increases the size of crystallites, and reduces the concentration of surface defects, which leads to improved optical and electrochemical characteristics of the material. Beyond conventional sensitivity metrics, our study demonstrates that the selective detection of ascorbic acid (AA) and uric acid (UA) can be achieved by controlling the applied potential on a single ZnO electrode, an approach that leverages differences in redox energetics and surface interaction dynamics rather than complex surface functionalization. It is shown in this work that the synthesized ZnO samples subjected to heat treatment in air at 450 °C exhibit high sensitivity to ascorbic acid (9951.87 μA·mM⁻¹·cm⁻²; LoD = 1.11 μM) at a potential of 0.2 V and to uric acid (5762.48 μA·mM⁻¹·cm⁻²; LoD = 1.71 μM) in a phosphate buffer solution (pH 7) at a potential of 0.4 V with a linear range of 3 mM, offering a way to create simplified multicomponent electrochemical biosensors based on potential-controlled selectivity.

Significant differences in hydrogen adsorption on amorphous and crystalline gold nanoparticles deposited on highly oriented pyrolytic graphite (HOPG) were revealed. Crystalline nanoparticles were synthesized via the impregnation–precipitation method followed by annealing at 700 K, whereas amorphous ones were obtained using the laser electrodispersion method. The morphology and electronic structure of single nanoparticles were investigated with high spatial resolution using scanning tunneling microscopy and spectroscopy (STM/STS) in ultra-high vacuum both before and after exposure to molecular hydrogen at doses of 400–6000 L. Experiments performed at room temperature showed that the surface coverage by the adsorbate in both cases begins at the Au-HOPG interface, spreads towards the center of the particle, and corresponds to the island growth model. However, amorphous nanoparticles have fewer growth sites at the periphery compared to crystalline ones. The local electronic structure of amorphous nanoparticles is more inhomogeneous compared to crystalline ones, demonstrating variation across different points on the nanoparticle surface. It was shown that dissociative chemisorption of hydrogen takes place on amorphous gold nanoparticles with a size of 4–6 nm. Chemisorption is completely inhibited when the nanoparticle size is reduced to 2 nm or less.

Atomic effects determining the adsorption of hydrogen and oxygen atoms on (111), (100), (110), and (211) surfaces of Cu and Pd have been studied using quantum chemical simulations. The deformation of the (111) and (100) surfaces during adatom bonding enhances the bond strength at active sites with high coordination numbers. In contrast, the deformation of the (110) and (211) surfaces does not exhibit a strong tendency. The atomic contribution of the nearest-neighbor environment depends on the square magnitude of the interaction matrix element, $V_{ad}^2$. A high $V_{ad}^2$ value increases the proportion of repulsive interactions within the metal adsorption complexes, leading to a decrease in the coordination number of the most stable adsorption site.

The design of small upper stages must meet many propulsion requirements: repeated restarts, stable operation at low mass flow rate, strict limits on mass and volume, and compatibility with limited ground infrastructure. The central engineering task is a justified selection of the liquid propellant rocket engine feed architecture for a given mission profile and propellant pair, since this choice affects specific impulse, service life, risk, and ground processing effort. This work systematizes propellant feed schemes for a small upper stage and proposes a unified analytical framework that links engine cycle and feed method with propellant selection and tank pressurization modes. Pressure fed and turbopump schemes are treated as mature solutions; pump cycles are used mainly with cryogenic propellants and in high energy demand cases that require high efficiency and compact hardware. In parallel, electro pump schemes are actively studied as a promising direction due to lower mechanical complexity, precise control, and straightforward integration with modern control systems. The analysis shows how chamber pressure, allowable throttling range, restart capability, and the mass and volume metrics of tanks and hardware bound the rational domain of each scheme. The outcome is a set of criteria for early design that maps mission requirements to feed system architecture and supports a technologically feasible choice for small upper stages. Keywords: pressure-fed system, turbopump-fed supply system, small upper stages, rocket engines, liquid rocket engine.

In this work, three types of zinc cobaltite ZnCo2O4 structures, namely, nanorods, nanowires, and plates, were synthesized on nickel foam using a simple hydrothermal method. The morphology and structural characteristics of the synthesized samples were studied. The grown structures can be used as a basis for enzyme-free electrochemical biosensors. A detailed analysis of a series of six samples synthesized at different Zn:Co ratios (1:1, 1:10, and 10:1) was performed using scanning electron microscopy. The results of the study of the elemental composition of ZnCo₂O₄ nanostructures synthesized by the hydrothermal method on nickel foam showed that the composition of the obtained materials correlates with the composition of the initial growth solution, confirming the controllability of the doping process. The absence of any impurities indicates a high purity of the synthesized samples. The data obtained confirm the possibility of precise control of the stoichiometry of zinc cobaltite. It is shown that the morphology of the grown samples depends on the stoichiometry of the precursors, providing controlled growth of nanostructured materials. It is shown that the hydrothermal method for the synthesis of ZnCo₂O₄ nanostructures allows obtaining materials with a wide range of stoichiometry from cobalt- to zinc-containing phases, which opens up opportunities for fine-tuning the effective, functional properties of ZnCo₂O₄.