  Negative differential thermal resistance (NDTR) can be generated for any
one-dimensional heat flow with a temperature-dependent thermal conductivity. In
a system-independent scaling analysis, the general condition for the occurrence
of NDTR is found to be an inequality with three scaling exponents:
$n_{1}n_{2}<-(1+n_{3})$, where $n_{1}\in(-\infty,+\infty)$ describes a
particular way of varying the temperature difference, and $n_{2}$ and $n_{3}$
describe, respectively, the dependence of the thermal conductivity on an
average temperature and on the temperature difference. For cases with a
temperature-dependent thermal conductivity, i.e. $n_{2}\neq0$, NDTR can
\emph{always} be generated with a suitable choice of $n_{1}$ such that this
inequality is satisfied. The results explain the illusory absence of a NDTR
regime in certain lattices and predict new ways of generating NDTR, where such
predictions have been verified numerically. The analysis will provide insights
for a designing of thermal devices, and for a manipulation of heat flow in
experimental systems, such as nanotubes.
