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.
A wide variety of chemical additives are used in hydraulic fracturing fluids. They include: dilute acids, biocides, breakers, corrosion inhibitors, crosslinkers, friction reducers, gels, potassium chloride, oxygen scavengers, pH adjusting agents, scale inhibitors and surfactants.