The authors apologize for the following errors. They do not affect the results.
(i) Abstract, l.7: ‘exit’ should be replaced by ‘exit slot’
(ii) § 2, l.6: ‘$|T_f|/N_f > \mu _p$’ should be replaced by ‘$|T_f|/N_f \geq \mu _p$’
(iii) Page 5, paragraph 4, l.18: ‘0.7’ should be replaced by ‘0.82’
(iv) Page 6, paragraph 2, l.16: ‘$H = 30\,d_p$’ should be replaced by ‘$H = 60\,d_p$’
(v) Page 20, table 1, 2nd column l.15: ‘144’ should be omitted.
(vi) Page 22, paragraph 1, l.9 and 10, and page 23, l.5: ‘$\boldsymbol{\mathsf{D}}$’ should be replaced by ‘${\mathsf{D}}$’
(vii) Page 34, (4.17) should be replaced by
\[ \epsilon_*^2 \frac{ {\rm d}^2 \tilde{f}}{ {\rm d} \tilde{x}^2} = \frac{\Delta \mu}{I_0 A^2} \frac{\phi_p}{\tilde{N}^{3/2}} \tilde{x} \tilde{f}^2 \](viii) Page 46, l.6 from the bottom: ‘participate’ should be replaced by ‘particulate’