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.
The early reciprocity laws found in the 19th century were usually expressed in terms of a power residue symbol (p / q) generalizing the quadratic reciprocity symbol, that describes when a prime number is an n th power residue modulo another prime, and gave a relation between (p / q) and (q / p).