This is the 130th most frequent Russian word.
тех
The word "тех" is the genitive plural form of "тот," meaning "those" in English.
Here, "тех" refers to a specific group of people ('those') in its genitive plural form, showing relation to the verb 'поддержал' (supported).
Мои друзья были среди тех, кто поддержал эту инициативу.
My friends were among those who supported this initiative.
The word "тех" is used in its genitive plural form to indicate possession or association with 'учёные' (scientists).
Я заинтересовался научными трудами тех учёных, которые работают над экологическими проектами.
I became interested in the scientific works of those scientists who are working on environmental projects.
In this sentence, "тех" modifies ‘моментах’ (moments) in its genitive plural form, specifying which moments are being referred to.