1 Stress echocardiogram: This is an echocardiogram that is performed while the person exercises on a treadmill or stationary bicycle. 2  This test can be used to visualize the motion of the heart's walls and pumping action when the heart is stressed.
Viruses require an active host program to cause damage and infect other executable files or documents, while worms are stand-alone malicious programs that can self-replicate and propagate via computer networks, without human help.
Propagare, in turn, derives from propages, meaning layer (of a plant), slip, offspring. It makes sense, therefore, that the earliest uses of propagate referred to facilitating the reproduction of a plant or animal. Nowadays, however, the meaning of propagate can extend to the reproduction of something intangible, such as an idea or belief. Incidentally, propaganda also comes to us from propagare, although it took a somewhat different route into English.