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$$
{\frac  {P_{{\mathrm  {gas}}}}{A_{{\mathrm  {F}}}}}={\biggl (}{\frac  {\mu _{e}m_{p}}{{\bar  {\mu }}m_{u}}}{\biggr )}{\biggl [}8\chi ^{3}{\frac  {T}{T_{e}}}{\biggr ]},
$$
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