If properly managed, clearing and replanting trees in a 30-year cycle creates both a renewable source of energy and maximum rubber production.

VOA: standard.2009.09.13

Well, then you could imagine a cycle here where activation of the receptor is leading to production of more ligand, is leading to activation of the receptor and production of a ligand.

那么,你就能画出一个循环图,激活受体能导致,更多配体的生成,这些配体又会刺激受体生成更多配体

耶鲁公开课 - 生物医学工程探索课程节选