Properties of a medium of food or feed, such as the fat content of meat, are determined by the use of dual X-ray absorptiometry with dual energy levels. The arithmetic logic unit is configured to propagate the Not-a-Number value as a Quiet-Not-a-Number value through its operations. The at least one free-standing carbon nanotube structure includes a net structure of a plurality of carbon nanotubes combined to each other due to the van der Waals attractive force. The display comprises one or more groups in the hierarchy, each represented by one of a set of circles above or below a level of the group that includes the individual. , a heartbeat signal to verify the alarm systems to the second communication nodes at first predetermined intervals.