The 70th Birthday of DSc Oksana Patsahan

Doctor of Sciences Oksana Patsahan -a renowned Ukrainian scholar in the fields of phase transition theory and physics of fluids -is celebrating her 70th birthday.A leading researcher in the Department for Computer Simulations of Many-Particle Systems at the Yukhnovskii Institute for Condensed Matter Physics (ICMP) of the National Academy of Sciences of Ukraine, she also serves as an active member of the Editorial Board for the Condensed Matter Physics journal.Oksana Patsahan (ne Vitenko) was born on February 15, 1956, in Kremenets, in the Ternopil region of Ukraine.She received her secondary education at Lviv Secondary School No. 70, graduating in 1973 with a gold medal for academic excellence.That same year, she enrolled in the Physics Department of Ivan Franko State University of Lviv, where she specialized in theoretical physics.While still a student, she began working as a laboratory assistant at the Department of Theoretical Physics, a position she held after her graduation.In 1984, she commenced her PhD studies at the same department, supervised by the eminent scientist Prof. Ihor Yukhnovskii, the founder of the Lviv school of statistical physics.Her research focused primarily on the phase behaviour of multicomponent fluids and the development of phase transition theory for such systems.In 1988, she successfully defended her PhD thesis, titled "The Application of the Collective Variables Method to the Description of Second-Order Phase Transitions in Binary Systems".This work proposed a theory that enabled the calculation of both universal and non-universal characteristics of binary fluids near a phase separation transition.Oksana Patsahan continued her career at the Lviv Division (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine since 1990, named after Yukhnovskii in 2025).There, she advanced her research on multicomponent fluids characterized by competing short-and long-range interactions.Systems with Coulomb interactions became a primary focus of her work.At the time, existing theories for these systems were predominantly limited to the mean-field level.Even for the Restricted Primitive Model (RPM) -arguably the simplest model in this class -it had not been possible to develop