  After negative temperature is restated, we find that it will derive
necessarily decrease of entropy. Negative temperature is based on the Kelvin
scale and the condition dU>0 and dS<0. Conversely, there is also negative
temperature for dU<0 and dS>0. But, negative temperature is contradiction with
usual meaning of temperature and with some basic concepts of physics and
mathematics. It is a question in nonequilibrium thermodynamics. We proposed a
possibility of decrease of entropy due to fluctuation magnified and internal
interactions in some isolated systems. From this we discuss some possible
examples and theories.
