Best example of positive feedback is the release of oxytocin during childbirth. Oxytocin is a reproductive hormone in females. Though it is also secreted in males, its function is yet unclear.
Brewing [edit]. In brewing, a carboy or demijohn is a glass or plastic vessel used in fermenting beverages such as wine, mead, cider, perry, and beer. Usually it is fitted with a rubber stopper and a fermentation lock to prevent bacteria and oxygen from entering during the fermentation process. 4.5 L (1.2 US gal) carboy is usually called a jug. A 57 L (15 US gal) carboy is usually called a demijohn (in the Philippines, dama juana. ). Demijohn is an old word that formerly referred to any glass vessel with a large body and small neck, enclosed in wickerwork.
Nightjohn is a story that is set in the south during the time of slavery. Based on an actual incident, Gary Paulsen tells about a young slave girl, Sarny, who it taught to read by another slave, Nightjohn. The book is very well written, complete with dialect that makes the book even more interesting to read. Nightjohn has escaped to the North where he was taught to read, but he keeps coming back to the south to further educate the slaves of the plantations.