On the binomial arithmetical rank

The binomial arithmetical rank of a binomial ideal I is the smallest intege r s for which there exist binomials f(l)....,f(s), in I such that rad (I) = rad (f(l),...,f(s)). We completely determine the binomial arithmetical ran k for the ideals of monomial curves in P-K(n). In particular we prove that. if the characteristic of the field K is zero, then bar (I(C)) = n - 1 if C is complete intersection, otherwise bar (I(C)) = n. While it is known that if the characteristic or the field K is positive, then bar (I(C)) = n - 1 always.