For most children, the National Heart, Lung, and Blood Institute recommends one cholesterol screening test between the ages of 9 and 11, and another cholesterol screening test between the ages of 17 and 21.
Wiktionary (0.00 / 0 votes) Rate this definition: fixation (Noun). The act of fixing, or the state of being fixed or fixated. fixation (Noun). The act of uniting chemically with a solid substance or in a solid form; reduction to a non-volatile condition; -- said of gaseous elements. fixation (Noun). The act or process of ceasing to be fluid and becoming firm.
Nitrogen fixation is the conversion of nitrogen that is found in  the atmosphere into ammonia-which is a form of nitrogen that can  be used by organisms.   Bacteria ar â¦ e cructial in this cycle because it is bacteria that  carry of this fixation. 3 people found this useful.