Pseudo-Anosov mapping classes from pure mapping classes
  We study types of mapping classes which arise as a product of a given mapping class and powers of certain pure mapping classes. We derive an explicit constant depending only on a surface such that almost all above pure mapping classes give rise to pseudo-Anosov type whenever their powers are larger than the constant. Furthermore, the stable lengths of pseudo-Anosov mapping classes obtained by this method are directly captured from the construction. 
Yohsuke Watanabe
math.GT math.GR