you cannot use a negated character class to match a q not followed by a u. Negative lookahead provides the solution: q(?!u).
Positive lookahead works just the same. q(?=u) matches a q that is followed by a u
X. Li, B. Liu, and S. Ng. Proceedings of the 2010 Conference on Empirical Methods in Natural Language Processing, page 218--228. Stroudsburg, PA, USA, Association for Computational Linguistics, (2010)