in epidemiology a group of individuals who share a characteristic acquired at the same time. The term usually refers to a birth cohort, which contains animals born in a specified time period. cohort studies. a prospective or follow-up, analytical, epidemiological study.n epidemiology a group of individuals who share a characteristic acquired at the same time. The term usually refers to a birth cohort, which contains animals born in a specified time period. cohort studies. a prospective or follow-up, analytical, epidemiological study.
From Wikipedia, the free encyclopedia. Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. It is a precursor to almost all fluorine compounds, including pharmaceuticals such as fluoxetine (Prozac), diverse materials such as PTFE (Teflon), and elemental fluorine itself.
Nitrogen trifluoride, with the chemical formula NF3, is an  inorganic compound which is trigonal pyramidal in shape.It has  three bond pairs and one lone pair.he shape of nitrogen trifluoride (NF3) is trigonal pyramidal. The  N atom is single bonded to three separate F atoms and has one lone  pair present. Edit.