Diffusion exponents (n) and
diffusion constants (k) are calculated from nonlinear regression of the curves from the experimental data, and are listed in Table 3.
Appearance of meningiomas on diffusion-weighted images: Correlating
diffusion constants with histopathologic findings.
Although the position is a continuous variable, the solution is unaware of the fringes except to the extent that there is a position-dependent effective velocity and effective
diffusion constant which is determined on the fine scale above.
We will see later that the right hand of equation is not the
diffusion constant and, thus, the Einstein relation is not satisfied.
Bulk water diffusion is characterized by one constant, the apparent
diffusion constant (ADC).
where [q.sub.t] is the amount of ion released at time t, [k.sub.p] is the overall
diffusion constant, and C is an empirical constant and would represent ion released from surface sites at t = 0 provided that it be a positive value (Jopony and Young 1987).
Notice that the
diffusion constant on the drop surface depends on the position, while it is considered to be constant in the bulk.
where: [m.sub.t] = mass of fluid that has diffused into the seal at any time t; [M.sub.[varies]] = mass of fluid that could possibly diffuse into the seal at time = infinity; R = outer maximum radius of the seal; r = the radius of the diffusing fluid front at any time t; D = the
diffusion constant for the fluid; [alpha] = a constant; and [J.sub.o] = a Bessel function.
D = the
diffusion constant in soil ([cm.sup.-2] [sec.sup.-1])
Equation 2 is the diffusion equation for ammonia diffusing to the surface of a film where [M.sub.t] is the mass of the ammonia at time t and [M.sub.[infinity]] is the mass of ammonia available, 1 is the thickness of the film, and D is the
diffusion constant.
The soil
diffusion constant (k, in kg [m.sup.-1]) can be estimated from the equation
Thus, the differential
diffusion constant of the nail is several hundred times that of skin.