Figure B.3

Concentration of radon, C/Co, as function of depth in the stomach wall. The radius of stomach lumen is 3.908 cm, corresponding to a volume of 250 mL. The concentration in the lumen is considered to be uniform and is assumed to decrease exponentially with a half-time of 20 min. The depth of the mucous layer is 50 µm, and that of the stem cell population is 200 µm.

wall becomes linear with distance from the surface when t is greater than 5 min. Figure B.4 shows the results of the model with the concentration C(t)/Co plotted as a function of time at various distances (in micrometers) from the inner surface of the wall.

The flow rate of radon through the stomach wall can be obtained from the following relationship:

where φ(r,t) is the flow rate of radon per unit area, often referred to as the flux density. Because radioactive decay has been neglected, one would expect the time-integrated flux to yield the total radon flowing through the wall and this should be independent of r:

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