g = r/r2 is
the dimensionless length (g1 = r1/r2). J0 and Y0 are the Bessel functions
of first and second kind of order zero, J1 and Y1 are the Bessel
functions of first and second kind of order one, q is defined as the
mass density of water uptake at time t, q1 is the mass density of
water uptake as time approaches infinity, and qo is the initial mass
density at the start of the process.