1 Girls start having periods at different times depending on how quickly they are developing.  If a girl has not had her first period by the time she is 16, this is still probably normal, but it would be worth checking with a doctor.
IETMS stands for Interactive Electronic Technical Manual System. Israeli English Teachers' Network. Institution of Engineering and Technology Northern Ireland. Institute of Engineering Technology of Ontario (Canada) Interagency Environmental Technology Office (Washington, DC) Industrial Effluent Treatment Plant.
Isoelectric focusing. Isoelectric focusing (IEF), also known as electrofocusing, is a technique for separating different molecules by differences in their isoelectric point (pI). It is a type of zone electrophoresis, usually performed on proteins in a gel, that takes advantage of the fact that overall charge on the molecule of interest is a function of the pH of its surroundings.