New evolution PDEs with many isochronous solutions

Certain nonlinear evolution PDEs in 1+1 variables (time and space) are identified, featuring a positive parameter to and evolving, for a large class of initial data, periodically with the fixed period T = 27 pi/omega (or perhaps (T) over tilde = pT with p a small integer). They are autonomous (i.e., they do not feature any explicit dependence on the time variable), but they generally (although not quite all of them) depend explicitly on the space variable hence are not translation-invariant. They are integrable, having been obtained by applying an appropriate change of dependent and independent variables to certain nonlinear evolution PDEs whose integrable character has been recently ascertained. Solutions of some of these PDEs are exhibited. (C) 2008 Elsevier Inc. All rights reserved.