a cancer biology phd student at stanford university is facing four felony poisoning charges after confessing to putting a known carcinogen into classmates ' water bottles over the course of weeks .
xiangyu ouyang , 26 , was on a state-sponsored scholarship from singapore when authorities say she began dosing the bottles with paraformaldehyde .
the recipient of singapore 's prestigious agency for science , technology and research -lrb- a * star -rrb- scholarship has been dropped from the top university and could face as many as 8 years in prison .