Darboux transformation and positons of the inhomogeneous Hirota and the   Maxwell-Bloch equation
  In this paper, we derive Darboux transformation of the inhomogeneous Hirota and the Maxwell-Bloch(IH-MB) equations which is governed by femtosecond pulse propagation through inhomogeneous doped fibre. The determinant representation of Darboux transformation is used to derive soliton solutions, positon solutions of the IH-MB equations. 
Chuanzhong Li, Jingsong He
nlin.SI