Amount of substance Amount of substance Amount of substance is a standard-defined quantity that measures the size of an ensemble of particles, such as atoms, molecules, electrons, and other particles. It is sometimes referred to as chemical amount. The International System of Units (SI) defines the amount of substance to be proportional to the number of entities present. The SI unit for amount of substance is the mole. It has the unit symbol mol. The proportionality constant is the inverse of the Avogadro constant. The mole is defined as the amount of substance that contains an equal number of elementary entities as there
Physics processing unit merged into nVidia). The unit is most effective in accelerating particle systems, with only a small performance improvement measured for rigid body physics. The Ageia PPU is documented in depth in their US patent application #20050075849. Nvidia/Ageia no longer produces PPUs and hardware acceleration for physics processing is now supported through some of their graphics processing units. The first processor to be advertised as a PPU was called the PhysX chip, introduced by a fabless semiconductor company called AGEIA. Games wishing to take advantage of the PhysX PPU must use AGEIA's PhysX SDK, (formerly known as the NovodeX SDK). It