Inter-beat (RR) Intervals. The time intervals between consecutive heart beats are customarily measured in the electrocardiogram from the beginning of a QRS complex to the beginning of the next QRS complex, so these intervals might be called QQ intervals, but they are conventionally named RR intervals.
Dubuque County, Iowa. Dubuque County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 93,653. The county seat is Dubuque. The county is named for Julien Dubuque, the first European settler of Iowa. Dubuque County comprises the Dubuque, IA Metropolitan Statistical Area, and is the seventh largest county by population in the state.
Waterloo, Iowa. Waterloo is a city in and the county seat of Black Hawk County, Iowa, United States. As of the 2010 United States Census the population decreased by 0.5% to 68,406; a recent 2014 Census estimates the population at 68,364, making it the sixth-largest city in the state.