Natural rubber Natural rubber Natural rubber, also called India rubber or caoutchouc, as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds, plus water. Malaysia and Indonesia are two of the leading rubber producers. Forms of polyisoprene that are used as natural rubbers are classified as elastomers. Currently, rubber is harvested mainly in the form of the latex from the rubber tree or others. The latex is a sticky, milky colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called "tapping". The latex then is
History of type theory derivations in logics. Howard showed that the typed lambda calculus corresponded to intuitionistic natural deduction. (That is, natural deduction without the Law of excluded middle.) The connection between types and logic lead to a lot of subsequent research to find new type theories for existing logics and new logics for existing type theories. Nicolaas Govert de Bruijn created the type theory Automath as a mathematical foundation for the Automath system, which could verify the correctness of proofs. The system developed and added features over time as type theory developed. Per Martin-Löf found a type theory that corresponded to predicate logic