The dynamics of the merger of a dwarf disc galaxy with a massive spiral galaxy of the Milky Way type were studied in detail. The remnant of such interaction after numerous crossings of the satellite through the disc of the main galaxy was a compact stellar core, the characteristics of which were close to small compact elliptical galaxies (cEs) or large ultra-compact dwarfs (UCDs). Such transitional cE/UCD objects with an effective radius of 100–200 pc arise as a result of stripping the outer layers of the stellar core during the destruction of a dwarf disc galaxy. Numerical models of the satellite before interaction included baryonic matter (stars and gas) and dark mass. We used N-body to describe the dynamics of stars and dark matter, and we used smoothed-particle hydrodynamics to model the gas components of both galaxies. The direct method of calculating the gravitational force between all particles provided a qualitative resolution of spatial structures up to 10 pc. The dwarf galaxy fell onto the gas and stellar discs of the main galaxy almost along a radial trajectory with a large eccentricity. This ensured that the dwarf crossed the disc of the main galaxy at each pericentric approach over a time interval of more than 9 billion years. We varied the gas mass and the initial orbital characteristics of the satellite over a wide range, studying the features of mass loss in the core. The presence of the initial gas component in a dwarf galaxy significantly affects the nature of the formation and evolution of the compact stellar core. The gas-rich satellite gives birth to a more compact elliptical galaxy compared to the merging gas-free dwarf galaxy. The initial gas content in the satellite also affects the internal rotation in the stripped nucleus. The simulated cE/UCD galaxies contained very little gas and dark matter at the end of their evolution.

This article presents the development of an anatomical breast phantom for investigating the capabilities of microwave radiometry in assessing thermal processes in biological tissues. The phantom accounts for the heterogeneous tissue structure and haemodynamics, enabling realistic heat transfer modelling. Numerical simulation software was developed, accurately reproducing experimental results and allowing the study of thermal anomalies. Experimental validation demonstrated that the temperature in the subcutaneous layer differed on average by 0.3 °C from deeper tissues, confirming the method’s effectiveness. The presence of a tumour in the model resulted in a local temperature increase of up to 0.77 °C, highlighting the sensitivity of microwave radiometry to tumour-induced thermal anomalies. These findings contribute to enhancing non-invasive techniques for early breast disease detection.

Modeling of collisionless galactic systems is based on the 𝑁-body model, which requires large computational resources due to the long-range nature of gravitational forces. The most common method for calculating gravity is the TreeCode algorithm, which provides a faster calculation of the force compared to the direct summation of contributions from all particles for 𝑁-body simulation. An analysis of the computational efficiency is performed for models with the number of particles up to 108. We considered several processors with different architectures in order to determine the performance of parallel simulations based on the OpenMP standard. An analysis of the use of extra threads in addition to physical cores shows an increase in simulation performance only when all logical threads are loaded, which doubles the total number of threads. This gives an increase in the efficiency of parallel computing by 20 percent on average.

When a Josephson vortex (fluxon) moves in a tunnel S-IS (S – superconductor, I – insulator) contact, in the I-layer of which there are random inhomogeneities, the radiation friction of the vortex against these inhomogeneities leads to a slowdown in its movement. To control the speed of the fluxon, a current can be introduced into the contact – the so-called fluxon shift current. In the article, the behavior of the fluxon shift current in a long S-I-S-tunnel junction with weak (low impurity concentrations) structural disorder in the I-layer is studied using a numerical-analytical method. Quantum resonant percolation trajectories (QRPTs), also called Lifshitz-Kirpichenkov trajectories, which are randomly formed in the I-layer containing impurity atoms, are considered as an inhomogeneity that influences the vortex dynamics. The fluxon shift current was considered in the parameter space (δ, c), where δ = µ − ε0 is the deviation of the Fermi level of the junction from the local single-electron impurity level. It is shown that there are physically significant concentration values at which the dependence of the shift current on δ has features (additional maxima) caused by the contributions of the QRPTs passing through different numbers of impurities. Not only quantitative but also qualitative (appearance and disappearance of features) changes in the dependence of the fluxon shift current on δ were also revealed. The results obtained can be useful in interpreting experimental data, as well as in creating technical devices based on disordered S-I-S-contacts.

This article presents a study on the influence of antenna parameters in medical microwave radiometers on brightness temperature. A series of computational experiments was conducted to analyse the dependence of brightness temperature on antenna characteristics. Various antenna parameters and their effect on the distribution of electromagnetic fields in biological tissues were examined. It was demonstrated that considering the antenna mismatch parameter is crucial when modelling the brightness temperature of biological tissues, contributing about 2 percent to its formation. The depth range of brightness temperature measurement was determined. The dependence of brightness temperature on the antenna diameter and frequency was established. The findings of this study can be applied to improve medical microwave radiometers and enhance their efficiency in the early diagnosis of various diseases.