The dual first-order release model illustrated two distinct release rates: an initial rapid release followed by a slow diffusion of PGN from the dispersion systems.
According to this idea, solute uptake by or release from the aquifer material is modelled at small scale by a "slow" diffusion process where the diffusion coefficient is reduced as compared to the aqueous diffusion coefficient due to (i) the size and shape of intra-particle pores and (ii) retarded transport of solutes within intra-particle pores governed by a nonlinear sorption isotherm.
Diffusion signal intensity with high b-values is dominated primarily by a slow diffusion component, as ADCst is related to the slow water diffusion.
It was found that the gas-solid carbonation mechanism of CSW and its mixture followed unreacted core model where a fast kinetically controlled process initially took place, then followed by a slow diffusion-controlled reaction process.
Within our description, the formation of nanoscale voids represents a slow (diffusion-controlled) process driven by release of the elastic energy of GB disclination configurations formed due to GB sliding.
The simulation involves realistic diffusion mechanisms, with a rapid diffusion of C atoms by interstitial jumps and a slower diffusion of Fe and Nb atoms by vacancy jumps; a simple model of the GB which reproduces the equilibrium segregation properties of Nb and C; and a point defect source which drives the vacancy concentration towards its equilibrium value.
The algorithm takes into account realistic diffusion properties, with a rapid diffusion of C atoms by interstitial jumps and a slower diffusion of Fe and Nb atoms by vacancy jumps.
The release of NGF from the crosslinked chitosan microspheres occurred in 3 stages: (1) a rapid burst release triggered by swelling, (2) a slower diffusion-based release through pores and channels within the microspheres, and (3) a further slowed release phase dominated by erosion-based release through chitosan biodegradation or in combination with diffusion of NGF [ 110].
Higher values of k id1 as compared to k id2 for Cr3+, Ni2+ and Zn2+ ions at all given temperature indicated the rapid boundary layer diffusion (phase 1) that was followed by a slow intraparticle diffusion (phase 2).
The solvent volume was decreased to precipitate the product as a green solid, which was separated by filtration and recrystallized by slow diffusion of hexane into a dichloromethane solution of the complex to give [Ni('S2Se2')] in 83 % yield.
However, the penetration of targeted nanoparticles deep into tissue can be hindered by their slow diffusion and a high binding affinity.
