Cells need to be close to a blood vessel to obtain sufficient oxygen. Model the tissue surrounding a blood vessel as a cylinder (radius R2) with a pipe (the blood vessel, radius R1) running through it, and imagine that there are many of these cylinders stacked together to form a larger volume of tissue. Oxygen consumption by the tissue can be modeled as an effectively zero order reaction.
(A) Propose suitable boundary conditions for the "tissue cylinder"
(B) Determine the concentration profile of oxygen (PO2(r)) and the flux of oxygen entering the tissue cylinder.