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.
Propagating Plants by Cuttings. Propagating plants from cuttings is one of the easiest and most used methods of propagation. Many plants will root from just a section of a plant. Some plants will root in water, but cuttings will develop a better root system when rooted in a soil-less potting mix.