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ab initio theoretical study
Published in Alberto Figoli, Jan Hoinkis, Sacide Alsoy Altinkaya, Jochen Bundschuh, Application of Nanotechnology in Membranes for Water Treatment, 2017
Giorgio De Luca, Federica Bisignano
The most easily accessible parameter correlated to the size of a solute is the molecular weight. However, it may mislead in terms of molecular rejection. In fact, although empirical correlations between weight and size are available for some compounds, they do not have general validity. Thus, in various studies, molecular sizes such as molecular width, Stokes radius and molecular mean size have been shown to be better descriptors of steric hindrance than molecular weight (Kiso et al., 1992; Ozaki and Li, 2002; Van der Bruggen et al., 1998). Stokes radius is a commonly used descriptor for the assessment of molecular steric hindrance. However, the diffusivities necessary to calculate the Stokes radius cannot be obtained for many organic solutes or for the same experimental conditions (Kiso et al., 1992). In addition, the Stokes radius is based on the assumption that solutes are spherical in shape, rigid and not hydrated, which is not always correct. Since the Stokes radius can be difficult to measure for some molecules, other molecular sizes have been developed to correctly take into account the steric hindrance and, in turn, solute rejection by a size exclusion mechanism. (Agenson et al., 2003; Gulseren et al., 2002; Santos et al., 2006; Yangali-Quintanilla et al., 2010).
Passive transport in the interstitium and circulation: basics
Published in Benjamin Loret, Fernando M. F. Simões, Biomechanical Aspects of Soft Tissues, 2017
Benjamin Loret, Fernando M. F. Simões
The formula has motivated a number of models that link the diffusion coefficient of polymers to their hydrodynamic radii. The hydrodynamic radius, or Stokes radius, or Stokes-Einstein radius, of a molecule is defined as the radius of a sphere whose diffusion coefficient given by the Stokes-Einstein relation (15.5.2) is equal to the effective diffusion coefficient of the molecule in the medium. Still, sometimes the hydrodynamic radius is chosen to match the diffusion coefficient in a blank solution.. Some data for macromolecules, BSA, Dextran, etc. diffusing in agarose gels are reported in Pluen at al. [1999].
Break-up behavior of droplets containing chlorine salt with the same valence cation under electric field via molecular dynamics simulation
Published in Journal of Dispersion Science and Technology, 2020
Yu Zhou, Hang Dong, Zhuojun Yang, Yonghong Liu
Therefore, the mobility of ions is inversely proportional to the Stokes radius instead of the crystallographic radius. The Stokes radius, as equivalent radius, is mainly affected by hydration number and crystallographic radius. The Stokes radius is proportional to hydration number, when the difference in hydration number of ions is relatively large. When the hydration number of ions is equal, the larger the crystallographic radius, the larger the Stokes radius. Figure 4 shows that the hydration number of ions decrease with the increasing crystallographic radius from Li+ to Rb+. Thus, from Li+ to Rb+, the Stokes radius gradually decreases. Moreover, the hydration number of Rb+ and Cs+ is almost equivalent. The Stokes radius of Cs+ is larger than Rb+, because of the large crystallographic radius of Cs+. Thus, as the crystallographic radius increases, the Stokes radius decreases first and then increases. Within a certain range, as the crystallographic radius increases, the mobility of ions gradually increases. However, the mobility does not increase all the time, and the maximum one is existed near Rb+.