Polycarbonate Diols (PCD) are used for a wide range of polyurethane-based coating formulations, providing an extreme durability and a high performance to the final polymer. ok
In mathematics, a reciprocity law is a generalization of the law of quadratic reciprocity. There are several different ways to express reciprocity laws.
In 1965, an anthropologist named Marshall Sahlins observed that there are three distinct types of reciprocity that occur in human societies around the world--generalized, balanced, and negative. Generalized reciprocity is gift giving without the expectation of an immediate return.