A method assigns importance ranks to documents within repositories or databases, such as any database of documents such as books or other printed material, electronic documentation, and pages within the world-wide web. One process comprises the step of contacting particles containing hydrocarbons with a stripping vapor in countercurrent flow to remove at least a portion of the hydrocarbons with the stripping vapor to form stripped particles. These compounds can be formulated in pharmaceutical compositions for the treatment of psychoses such as, for example, schizophrenia. The air is introduced into the chamber in a substantially axial orientation and waste gases in a substantially tangential or radial orientation. In addition, the vacuum gripper device of the present invention can be designed compactly and safely although the device includes the vacuum pump.