The ratio Deff(r)∕D(r) as a function of the dimensionless particle radius, x=r∕a, for the case of dead ends with no cavities, Vcav=0. The curves from top to bottom correspond to α=0,2,5,10,20. All curves merge into one, Deff(r)∕D(r)=1, at x>1 since Deff(r)=D(r) at r>a.