An efficient operation of a Ho:YLF laser pumped by a Tm-doped fibre laser is reported. The research in a continuous-wave (CW) operation was done for two crystals of the same 0.5 at.%Ho dopant concentration and with different lengths (3×3×30 mm³ and 3×3×50 mm³). For an output coupling transmission of 20% and a crystal length of 50 mm, the maximum CWoutput power of 38.9 W for 81.4 W of incident pump power, corresponding to the slope efficiency of 52.3% and optical-to-optical conversion efficiency of 47.8% (determined with respect to the incident pump power) was achieved. The highest opti- cal-to-optical conversion efficiency of 70.2% with respect to the absorbed pump power was obtained. The influence of a heat-sink cooling water temperature on theCWlaser performance was studied. For a Q-switched operation the pulse repe- tition frequency (PRF) was changed from 2 to 10 kHz. The maximum average output power of 34.1 W at the PRF of 10 kHz was obtained for a 50 mm holmium crystal length. For 2 kHz PRF and 71.9 W of incident pump power, pulse energies of 13.7 mJ with a 21 ns FWHM pulse width corresponding to 652 kW peak power were recorded.

The investigations were carried out at Bonin during I 996-1999. The aim of the study was the comparison of PVY, PVS, PVM and PLRV infection pressure in different periods of growing season. The PVY pressure was the greatest. The mean (of 4 years) infection was 32%. Evidently lower infection was observed for PVS (19%) and PVM (7%) and extremely low for PLRV (only O.Ol%). The most intense spread of PVY, PVS and PVM took place from second IO days of July until first ten days of August.

Four dye-sensitized solar cell devices are designed and fabricated based on natural dyes extracted from Celosia Cristata, Saffron, Cynoglossum, and eggplant peel, as photosensitizers. The UV–vis technique has been served to determine maximum absorption of natural extract and pre-dyed photoanode. The Fourier transform infrared (FT-IR) was employed to cover the presence of functional groups. The cyclic voltammetry method has been employed to assess the possibility of charge transfer from dried natural dyes to the photoelectrode. The performance of natural-based dye-sensitized solar cells is determined subsequently. The highest power conversion efficiency was ca. 1.38%, which belonged to Celosia Cristata extract. The devices were examined for higher efficiencies, individually, co-sensitized arrangement and/or in tandem with each other.

Shape memory alloys are characterised by interesting properties, i.e. shape memory effect and pseudoelasticity, which enable their increasing application. Thermomechanical aspects of martensitic and reverse transformations in TiNi shape memory alloy subjected to tension tests were investigated. The stress-strain characteristics obtained during the tests were completed by the temperature characteristics. The temperature changes were calculated on the basis of thermograms determined by an infrared camera. Taking advantages from the infrared technique, the temperature distributions on the specimen’s surface were found. Heterogeneous temperature distributions, related to the nucleation and development of the new martensite phase, were registered and analysed. A significant temperature increase, up to 30 K, was registered during the martensitic transformation. The similar effects of the heterogeneous temperature distribution were observed during unloading, while the reverse transformation, martensite into austenite took place, accompanied by significant temperature decrease.

Professor Piotr Francuz conducted innovative experimental research in cognitive psychology and neuroscience. He was the author of numerous publications on perception and information processing, audiovisual communication, imagination and perception of beauty, and psychology methodology. The paper presents the Professor's scientific profile and his research, teaching, and organizational achievements. Professor passed away on November 14, 2020.

Professor Lech Wojtczak spent his entire scientific life at the Nencki Institute of Experimental Biology PAS, where he worked since 1947. He is the author or co-author of two hundred scientific papers, promoted 15 doctors of science, was the Full Member of PAS and has been awarded with several prizes and honors. Among his students are three successive directors of the Nencki Institute, the authors of the present article. Scientific interests of Professor Lech Wojtczak were always dealing with bioenergectics, a discipline that he led in Poland and Eastern-Central Europe. In particular, his studies focused on the role of fatty acids and their derivatives on bioenergetics, on the regulatory role of surface potential of biomembranes on enzymatic and transport activities, on the regulatory role of calcium and magnesium in mitochondria, on the role of free oxigen radicals in bioenergetics, etc. Apart from being a great scientist, Lech Wojtczak was also a fantastic teacher, and an excellent scientific supervisor. Being well recognized in the world, he was placing members of his research group in foreignlaboratories, as well as was sending tchem to courses and conferences. This was opening their minds to the world, and to other cultures, and allowed Lech Wojtczak to form from his collaborators the next generation of good scientists and future leaders. The list of the most important pupils of Professor Wojtczak is given in the article. Lech was also excellent in social contacts, and in creating a friendly atmosphere. Together with his wife Anna, they kept an open home, often inviting collaborators to parties that usually led to long scientific discussions. With the sudden death of Pofessor Lech Wojtczak Polish science suffered a great loss. This eminent researcher, the father of Polish bioenergetics, but also a warm and modest person, will be dearly missed.