We consider the problem of converting a deterministic finite automaton (DFA) into a short regular expression (RE). Examples given by Ehrenfeucht and Zeiger in the 1970s show that the required expression size in the worst case is 2Θ(n) for infinite languages, and for finite languages in nΩ(log log n) and nO(logn), if the alphabet size is allowed to grow with the number of states n of the given a...

Given a nonsingular n × n matrix of univariate polynomials over a field K, we give fast and deterministic algorithms to compute its determinant and its Hermite normal form. Our algorithms use Õ(nωdse) operations in K, where s is bounded from above by both the average of the degrees of the rows and that of the columns of the matrix and ω is the exponent of matrix multiplication. The soft-O notat...

The superoxide radical anion (O # −d) produced during the catalytic activity of nitric oxide synthase (NOS) and cytochrome P-450 has been implicated in the oxidative denitrification of hydroxyguanidines ("C ̄NOH). The reactivity of the radiolytically generated O # −d radical with N-hydroxy--arginine (NHA) is pH dependent and appears to parallel the prototropic equilibrium of the hydroxyguanidin...