Enzyme unit SI unit, the enzyme unit is discouraged in favour of the katal, the unit recommended by the General Conference on Weights and Measures in 1978 and officially adopted in 1999. One katal is the amount of enzyme that converts 1 mole of substrate per second, so The enzyme unit should not be confused with the international unit (IU); although it is true that both measure chemical activity and that for many enzymes 1 U = 1 IU (because for many enzymes the existing U was adopted as the newer IU), international units can be defined for the biologic activity of
Bubble (physics) Bubble (physics) A bubble is a globule of one substance in another, usually gas in a liquid. Due to the Marangoni effect, bubbles may remain intact when they reach the surface of the immersive substance. Bubbles are seen in many places in everyday life, for example: Bubbles form, and coalesce, into globular shapes, because those shapes are at a lower energy state. For the physics and chemistry behind it, see nucleation. Bubbles are visible because they have a different refractive index (RI) than the surrounding substance. For example, the RI of air is approximately 1.0003 and the RI of water