Absolute zero is the coldest possible temperature, at which no heat is left in a substance and its particles display no motion whatsoever. Absolute zero is equal to 0 K on the Kelvin scale, which is... Absolute zero is the coldest possible temperature, at which no heat is left in a substance and its particles display no motion whatsoever.
Serum is plasma that has been allowed to clot. It is prepared in the same way as plasma; however, the blood is collected into a tube with no anticoagulant. While spinning in the centrifuge, the clot moves with the cells to the bottom of the blood collection tube, leaving the serum on top.
A serum iron test measures how much iron is in your serum. Serum is the liquid that is left over from your blood when red blood cells and clotting factors have been removed. The serum iron test can reveal abnormally low or high blood iron levels. Your doctor will most likely order this test after another lab test shows an abnormal result.