A multilevel computer security system including a computer with multiple security subsystems for secure data storage and data communications at each security level, a smart-card reader for controlling user access to each security level, and an electronically-activated switch for activating only the selected and authorized security level. The first rotor includes a guide that extends in a circular arc around the first shaft L1 and a drive pin that is provided outside the guide relative to the first shaft L1. The plurality of pipelines connected to the plurality of hoods is to take the polluted air therefrom. The blood vessel is then cross-sectioned and used to identify its tissue type and to create a corresponding image. Seed andor fertilizer conduits are attached to or incorporated in the trailing face of the blade in which the outlets may be spaced for controlled placement of the materials.