At the object level . Permissions allowed or denied at the object level apply to the entire object. For example, you can set an object-level permission on an OU object that allows a particular group, such as Account Operators, to create child objects in the OU. At the property level .
Ball mills are used in chemistry and in industry to grind hard solids to a very fine powder. They are very similar to rock tumblers. Basically, the idea is to rotate a container filled with heavy metal balls that crush the substance that you want to grind.
Sulfuric acid is the most abundant product of the chemical industry. It is used in the refining of metals and in the manufacture of a wide variety of substances. It is used for the pickling of steel to retard corrosion, in the refinement of petroleum, and in the manufacture of fertilizers.