For example, a certain maize variety grown in a cool climate will need less water per day than the same maize variety grown in a hotter climate. It is therefore useful to take a certain standard crop or reference crop and determine how much water this crop needs per day in the various climatic regions.
An implantable cardioverter defibrillator (ICD) looks very similar to a pacemaker, except that it is slightly larger. It has a generator, one or more leads, and an electrode for each lead. These components work very much like a pacemaker.
A pacemaker is a device which sends electrical signals to the heart triggering heartbeats when needed. There are many ways to implant and configure a pacemaker; it may beat the top chambers (atria), lower chambers (ventricles) or both. Some systems stimulate both the left and right ventricles together.