Kyiv Academic University

The response of a MoRe-based microstrip superconducting resonator operating near 5 K to pulsed infrared irradiation is investigated, and the underlying physical mechanisms are analyzed. The device exhibits a pronounced nonlinear response dominated by nonequilibrium quasiparticle dynamics rather than uniform thermal heating. Infrared pulses produce strong distortions of the resonance curve and a transient decrease in the resonance frequency, consistent with increased kinetic inductance caused by quasiparticle generation. The frequency shift scales approximately linearly with absorbed power, whereas the dissipation response saturates at higher powers, indicating the formation of a nonequilibrium steady-state quasiparticle population. These observations demonstrate a transition from a linear pair-breaking regime to a saturated dissipation regime, likely associated with a quasiparticle relaxation bottleneck. The results highlight the relevance of nonequilibrium processes in MoRe and confirm its potential for microwave kinetic-inductance detector applications.

Abstract During gestation, the human placenta develops as a fetal organ in direct contact with maternal cells and tissues. Most pregnancy complications, such as preeclampsia and fetal growth restriction, have their roots early in pregnancy, most probably in dysregulation of placental development and/or disturbances in the interaction with maternal (immune) cells. Here, we applied an integrative analysis of open-access gene expression data on the human placenta, comparing expression levels between the first and second trimesters of healthy pregnancy, with a focus on differentially expressed genes related to immune processes. The holistic approach of our study revealed differentially expressed genes involved in the recognition and elimination of potential PAMPs and DAMPs, transendothelial cell migration, cytokine production, transplacental IgG transport, and maintenance of immune tolerance during the transition from the first to the second trimester of placental development. Most DEGs show an increased expression. Only a few genes, DEFB1 , SLPI , and LCN2, which encode antimicrobial proteins, homeostatic chemokines, and a pleiotropic PAEP that maintains tolerance, display maximal expression in the first trimester, followed by further down-regulation. The cell types deconvolutions revealed the typical representation of placental cells.

Recently, severe plastic deformation engineering has emerged as a powerful tool to control the main mechanical properties of metals and alloys. In particular, it concerns the high-pressure torsion method where the material is torsionally strained under high pressure between two anvils. It has been found that the reduction in crystallinity of metallic materials by the shear strain in combination with their nanostructuring results in an inherent high strength together with low-temperature superplasticity or improved creep resistance. In this work, using the point-contact spectroscopy technique, we analyze how the local superconducting characteristics of a Mo-Re alloy are modified after high-pressure torsion processing. We record the restoration of suppressed superconductivity on the surface of the samples, a significant strengthening of the electron-phonon coupling in them, and a slight increase in the superconducting transition temperature. The obtained results are explained based on modern concepts about the decisive influence of phonon softening on the basic properties of intrinsically disordered superconductors.

Exchange bias (EB) related to magnetization reversal fields was found in a single-crystal of ${\mathrm{Ni}}_{4}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$, a compensated ferrimagnet consisting of two $\mathrm{N}{\mathrm{i}}^{2+}$ ferromagnetic sublattices with opposite moments, associated with two differently distorted honeycomb-like layers in the ab plane, alternating along the $c$ axis. The EB field is significant near the compensation temperature ${T}_{\mathrm{comp}}=33\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, it increases rapidly as the temperature approaches ${T}_{\mathrm{comp}}$, and changes sign when crossing ${T}_{\mathrm{comp}}$, showing a large gap of 3.5 kOe. The magnetization reversal field also diverges at ${T}_{\mathrm{comp}}$ and reaches 10 kOe. The hyperbola-like spin reversal lines obtained in the $T\text{\ensuremath{-}}H$ plane are asymmetric with respect to the $H=0$ and $T={T}_{\mathrm{comp}}$ axes due to EB and demonstrate both the field and temperature EB effect. These lines exhibit mirror symmetry when the sign of ${H}_{\mathrm{cool}}$ changes, which makes it possible to determine the EB energy to be about 100 erg/g. Noninterface EB in single-phase ${\mathrm{Ni}}_{4}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$ is discussed within the model of two antiferromagnetically coupled $\mathrm{N}{\mathrm{i}}^{2+}$ sublattices with oppositely oriented ferromagnetic moments and is compared with a similar EB observed in another type of compensated ferrimagnet -- orthoferrite ${\mathrm{ErFeO}}_{3}$.

The article is dedicated to the study of the peculiarities of charity development and the functioning of international charitable organizations that have acquired the status of an international entity. Such non-governmental actors are able to respond adaptively and act more quickly and locally on the world stage to address the most pressing issues, providing assistance and support to the most vulnerable categories and in the most critical geopolitical spaces. With the help of an interdisciplinary approach, it was possible to identify the historical background of the origin of the phenomenon of selfless human activity, a systematic political and legal analysis of international and domestic legislation helped to identify the peculiarities of the functioning of international charitable organizations in the United States, Europe and Ukraine, and a generalization of the obtained results crystallized the foundations and features of their direct involvement in problem areas.The difference between international non-governmental organizations and international charitable organizations was proved. The author identifies the main sources of funding for such structures through grants, donations from individuals and legal entities, international organizations and governments. It is established that the tasks of establishing and operating international charitable organizations are implemented in three areas of activity, including non-refundable assistance, administration of response and recovery projects, lobbying and actualization of the problem for the world community through influence on the political establishment and public opinion.

Abstract Topological materials, such as topological insulators or semimetals, usually not only reveal the nontrivial properties of their electronic wavefunctions through the appearance of stable boundary modes, but also through very specific electromagnetic responses. The anisotropic longitudinal magnetoresistance of Weyl semimetals, for instance, carries the signature of the chiral anomaly of Weyl fermions. However for topological nodal line (TNL) semimetals – materials where the valence and conduction bands cross each other on one-dimensional curves in the three-dimensional Brillouin zone – such a characteristic has been lacking. Here we report the discovery of a peculiar charge transport effect generated by TNLs: a dissipationless transverse signal in the presence of coplanar electric and magnetic fields, which originates from a Zeeman induced conversion of TNLs into Weyl nodes under infinitesimally small magnetic fields. We evidence this dissipationless topological response in trigonal PtBi2 persisting up to room temperature, and unveil the extensive TNLs in the band structure of this non-magnetic material. These findings provide a new pathway to engineer Weyl nodes by arbitrary small magnetic fields and reveal that bulk topological nodal lines can exhibit non-dissipative transport properties.

We present investigation of the inoculation of nano-sized powders of refractory oxides $\mathrm{Al}_{2} \mathrm{O}_{3}, \mathrm{TiO}_{2}, \mathbf{M g O}$, ZrO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> into the welding pool. We show that oxides’ inoculation with a low level of mismatch to the $\delta$-Fe lattice and increased wetting with liquid iron ($\mathrm{MgO}, \mathrm{ZrO}_{2}$) into the weld pool contributes to the dendrites growth, which are formed during melt crystallization. Metal modification with $\mathbf{M g O}, \mathbf{Z r O}_{2}$ oxides contributes to decrease of the polygonal ferrite hardness and increase in the lower bainite content in the microstructure. This leads to overall increase of metal resistance against brittle fracture. Metal modification with Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> and TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> contributes to increase of polygonal ferrite hardness and the upper bainite content in the microstructure, resulting in improvement of strength indicators of low-alloy steel welds.