Acetylcholine is an organic chemical that functions in the brain and body of many types of animals, including humans, as a neurotransmitterâa chemical released by nerve cells to send signals to other cells. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Parts in the body that use or are affected by acetylcholine are referred to as cholinergic. Substances that interfere with acetylcholine activity are called anticholinergics. Acetylcholine is the ...
Every interior algebra can be represented as a topological field of sets with its interior and closure operators corresponding to those of the topological space. Given a topological space the clopen sets trivially form a topological field of sets as each clopen set is its own interior and closure.
For similar symbols, see OE (Ã¸) . Disambiguation the empty set is the set containing no. Elements in, mathematics and more specifically set, theory the empty set is the unique set having no; elements its size or (cardinality count of elements in a) set is. zero