= Isobaric conductive cooling in mass coordinates
{title2=$T_\tau+\Lambda(T)/T-\lambda_0\partial_m(T^{\alpha-1}T_m)=0$}
With fixed <pressure> $p$, let $A=\mu p/\mathcal R$, so $\rho=A/T$. A material mass coordinate has $\partial_x=\rho\partial_m$ and the material time derivative becomes $\partial_t|_m$. The energy and continuity equations then give the displayed equation with $\tau=Ct$ and $C=(\gamma-1)(\mu/\mathcal R)^2p/\gamma$. A mass integral from a fixed origin is material only when the <mass flux> there vanishes; otherwise subtract its time-integrated flux to label parcels. Uniform <pressure> is a low-Mach approximation when sound crossing is faster than thermal evolution.
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