Remark on the Second Principle of Thermodynamics
  All presently available results lead to the conclusion that nonextensivity, in the sense of nonextensive statistical mechanics (i.e., $q \ne 1$), does {\it not} modify anything to the second principle of thermodynamics, which therefore holds in the usual way. Moreover, some claims in the literature that this principle can be violated for specific anomalous systems (e.g., granular materials) can be shown to be fallacious. One recent such example is analyzed, and it is suggested how $q \ne 1$ distributions could in fact restore the validity of macroscopic time irreversibility, a cornerstone of our present understanding of nature. 
Constantino Tsallis (Centro Brasileiro de Pesquisas Fisicas, Rio de   Janeiro-Brazil)