Source: https://www.researchgate.net/profile/Huajian-Gao/publication/24173221_Size_and_shape_effects_on_diffusion_and_absorption_of_colloidal_particles_near_a_partially_absorbing_sphere_Implications_for_uptake_of_nanoparticles_in_animal_cells/links/545a81410cf2c46f664381e3/Size-and-shape-effects-on-diffusion-and-absorption-of-colloidal-particles-near-a-partially-absorbing-sphere-Implications-for-uptake-of-nanoparticles-in-animal-cells.pdf