this is THE consequence of the historic definition of temperature ..., maybe

Let us go a little bit deeper into the "Very strange paper :) : Negative Absolute Temperature for Motional Degrees of Freedom":
S. Braun et al,
Science 4 January 2013: 
Vol. 339 no. 6115 pp. 52-55 
DOI: 10.1126/science.1227831

Hope you shall enjoy the screenshots:

Screenshot # 1, Quote [this is a consequence of the historic definition of temperature]

Screenshot # 2, a delicately useful (historic, lonian), Encyclopedic abbreviation of the kinetic energy. 

Screenshot # 3, results that can trigger unimaginably applicable, perspective breakthrough innovations in near future:

Definitely mankind is entering into new stage of its accelerated development that opens tremendous opportunities for technological breakthroughs.