  Kapitza resistance in the chain models with internal defects is considered.
For the case of the linear chain, the exact analytic solution for the boundary
resistance is derived for arbitrary linear time-independent conservative
inclusion or defect. A simple case of isolated isotopic defects is explored in
more detail. Contrary to the bulk conductivity, in the linear chain, the
Kapitza resistance is finite and well-defined. At the same time, the resistance
strongly depends on the parameters of the thermostats, and therefore cannot be
considered as a local property of the defect. Asymptotic behavior of the heat
flux in the case of very heavy defect is explored and compared to the nonlinear
counterparts; similarities in the scaling behavior are revealed. For the
lightweight isotopic defect in the linear chain, one encounters a typical dip
of the temperature profile, related to weak excitation of the localized mode in
the attenuation zone. If the nonlinear interactions are included, this dip can
still appear at a relatively short time scale, with subsequent elimination due
to the nonlinear interactions. This observation implies that even in the
nonlinear chains, the linear dynamics can predict the main features of the
short-time thermal profile if the temperature is low enough.
