The relationship between local microstructure and superconducting properties of commercially prepared YBa ₂ Cu ₃ O _{7− δ} single-grain bulk superconductor was investigated. The small samples for magnetization measurements were taken from the beginning and end of the a -growth sector and the c -growth sector as well as from the beginning and end of a / a -growth sector boundary. The field dependence of the magnetic moment was measured at temperatures starting from liquid helium (4.2 K) to liquid nitrogen (77 K) using the commercial Magnetic Property Measurement System with a magnetic field of up to 7 and 18 T. The microstructure was analysed using polarised light optical microscopy and scanning electron microscopy. The quantitative microstructural data were determined using an image processing software package. Microstructure analysis was focused on the size and volume fraction of Y ₂ BaCuO ₅ particles as well as on the characterisation of subgrain structure. These measurements showed that not only inhomogeneous distribution of Y ₂ BaCuO ₅ particles had influence on the critical current density but it can also be significantly affected by the subgrain structure within the bulk or by local contamination of YBa ₂ Cu ₃ O _{7− δ} from the seed during fabrication process. It was observed that the critical current density along the a / a -growth sector boundary could be substantially higher in comparison to the other parts of the bulk and this behaviour can be related to the subgrain structure in the sample.

The global pandemic of SARS-CoV-2 has highlighted the necessity for innovative therapeutic solutions. This research presents a new formulation utilising the metal-organic framework MIL-101(Al)-NH₂, which is loaded with hypericin, aimed at addressing viral and bacterial challenges. Hypericin, recognised for its antiviral and antibacterial efficacy, was encapsulated to mitigate its hydrophobicity, improve bioavailability, and utilise its photodynamic characteristics. The MIL-101(Al)-NH₂ Hyp complex was synthesised, characterised, and evaluated for its biological applications for the first time. The main objective of this study was to demonstrate the multimodal potential of such a construct, in particular the effect on SARS-CoV-2 protein levels and its interaction with cells. Both in vitro and in vivo experiments demonstrated the effective transport of hypericin to cells that express ACE2 receptors, thereby mimicking mechanisms of viral entry. In addition, hypericin found in the mitochondria showed selective phototoxicity when activated by light, leading to a decrease in the metabolic activity of glioblastoma cells. Importantly, the complex also showed antibacterial efficacy by selectively targeting Gram-positive Staphylococcus epidermidis compared to Gram-negative Escherichia coli under photodynamic therapy (PDT) conditions. To our knowledge, this study was the first to demonstrate the interaction between hypericin, MIL-101(Al)-NH₂ and the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein, which inhibits cellular uptake and colocalises with ACE2-expressing cells. Therefore, the dual functionality of the complex - targeting the viral RBD and the antibacterial effect via PDT - emphasises its potential to mitigate complications of viral infections, such as secondary bacterial infections. In summary, these results suggest that MIL-101(Al)-NH₂ Hyp is a promising multifunctional therapeutic agent for antiviral and antibacterial applications, potentially contributing to the improvement of COVID-19 treatment protocols and the treatment of co-infections.

YBCO bulk single-grain samples with and without cerium oxide addition, were prepared by the two-step top seeded infiltration growth. The microstructure observations showed that cerium oxide addition led to formation of small Y ₂ BaCuO ₅ (Y211) particles in the YBa ₂ Cu ₃ O ₇ single-grain matix. On the other hand, the sample without cerium oxide addition exhibited clusters of large Y211 particles. Observed difference in Y211 paricles led to significantly different size of a/c-oxygenation cracks. While the mean length of a/c-cracks in the sample with cerium oxide addition was several hundred micrometers, it was smaller than 50 μ m in the sample without cerium oxide addition. It was shown that the clusters of large Y211 particles can effectively prevent extension of oxygenation a/c-cracks. The trapped magnetic field measured at 77 K is shown.