- A chain of thermonuclear reactions in which nitrogen isotopes are formed in intermediate stages and carbon acts essentially as a catalyst to convert four hydrogen atoms into one helium atom with the emission of two positrons. The entire sequence is thought to generate significant amounts of energy in the sun and certain other stars.carbon cycle nitrogen cycle
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
- See carbon cycle.
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