Strange quark
The first strange particle (a particle containing a strange quark) was discovered in 1947 (kaons), but the existence of the strange quark itself (and that of the up and down quarks) was only postulated in 1964 by Murray Gell-Mann and George Zweig to explain the Eightfold Way classification scheme of hadrons. The first evidence for the existence of quarks came in 1968, in deep inelastic scattering experiments at the Stanford Linear Accelerator Center. These experiments confirmed the existence of up and down quarks, and by extension, strange quarks, as they were required to explain the Eightfold Way.
André-Louis Debierne
Debierne studied at the elite École supérieure de physique et de chimie industrielles de la ville de Paris (ESPCI ParisTech). He was a student of Charles Friedel, was a close friend of Pierre and Marie Curie and was associated with their work. In 1899, he discovered the radioactive element actinium, as a result of continuing the work with pitchblende that the Curies had initiated.