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ABSTRACT: The electrophoresis of a charge-regulated spherical particle, which mimics biocolloids and particles covered by an artificial membrane, at an arbitrary position in a spherical cavity filled with a shear-thinning Carreau fluid is modeled under the conditions of low surface potential and weak applied electric field. We examine simultaneously the influences of the presence of a boundary, the nature of the fluid, and the charged conditions on the boundary and the particle surface on the electrophoretic behavior of the particle. The mobility of the particle in a shear-thinning Carreau fluid is larger than that in the corresponding Newtonian fluid, and the difference between the two increases with increasing mobility. For the present case, the particle is negatively charged, and due to the presence of an electroosmotic flow, the electrophoretic behavior of the particle for the case where the boundary is positively charged is more complicated than that when it is uncharged or negatively charged. The factors key to the mobility of the particle include the position and the relative size of the particle, the thickness of double layer, the nature of the fluid, the density of the dissociable functional groups on the particle surface and the associated equilibrium constant, and the pH of the bulk phase.
Colloids and surfaces. B, Biointerfaces 12/2008; 69(1):8-14. · 2.60 Impact Factor
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ABSTRACT: The electrical interaction between two long, parallel cylinders each is covered by an ion-penetrable charged membrane immersed in an oil/water interface is investigated. The effects of contact angle, radius of cylinder, and membrane thickness on the electrical interaction force are examined. The results of numerical simulation reveal that the following conditions lead to a greater electrical interaction force: (i) a larger contact angle, i.e. a larger fraction of a cylinder in the oil phase; (ii) a larger cylinder radius; and (iii) a thinner membrane. For a fixed ionic strength, the electrical interaction force is insensible to the type of electrolytes in the water phase, in general. However, if two cylinders are close enough, then the higher the valence of counterions the greater the electrical interaction force.
Colloids and surfaces. B, Biointerfaces 09/2001; 21(4):265-272. · 2.60 Impact Factor
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ABSTRACT: The electrophoretic behavior of a planar particle covered by an ion-penetrable membrane, which simulates a biological entity, is investigated. We show that, in general, a point charge model will overestimate the electrophoretic mobility of a particle and the deviation increases with the increase in the concentration of fixed charge and with the decrease in the thickness of membrane layer. As in the case of a point charge model, the present model also predicts a local maximum in the absolute mobility as the thickness of membrane layer varies. If the sizes of counterions of various valences are the same, then the lower the valence of counterions, the larger the mobility, and the larger the counterions, the greater the mobility. The latter is consistent with the experimental observations in the literature. For the level of the concentration of fixed charge examined, the effect of coions on the mobility is negligible.
Electrophoresis 07/2001; 22(10):1881-6. · 3.30 Impact Factor
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ABSTRACT: The electrokinetic flow of an electrolyte solution in a planar slit covered by an ion-penetrable charged membrane layer is analyzed theoretically. An approximate analytical expression for the spatial variation in the electrical potential is derived, and the electroosmotic velocity, the total electric current, and the streaming potential of the system under consideration are evaluated. The effects of epsilon' (relative permittivity of liquid phase/relative permittivity of membrane layer), eta' (viscosity of liquid phase/viscosity of membrane layer) and the valence of anions (coions) on the volumetric flow rate and total current are examined. We show that the effect of the valence of cations (counterions) on the volumetric flow rate is less significant than that of epsilon' and that of eta'. However, the effect of epsilon' on the total current is less significant than that of the valence of cations and that of eta'. The variation of total current as a function of ionic strength is found to have a local minimum, regardless of whether a pressure gradient is applied or not. The absolute streaming potential has a local maximum as the concentration of fixed charge varies, which was not found in previous studies.
Electrophoresis 12/2000; 21(17):3541-51. · 3.30 Impact Factor
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Journal of the Electrochemical Society. 01/2000; 147:1920--1924.
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ABSTRACT: The electrophoretic mobility of a particle covered by a membrane in an a:b electrolyte solution is modeled theoretically. The membrane, which simulates the surface of a biological cell, is ion-penetrable, and carries homogeneously distributed negative fixed charges. An approximate expression for the electrophoretic mobility is derived. Based on the results of numerical simulation, we conclude the following: (1) The absolute Donnan potential increases with the concentration of the fixed charges C0, but decreases with the ionic strength I. (2) The greater the valence of cation alpha, the lower the absolute potential distribution. (3) The greater the C0, the greater the absolute mobility of a particle, magnitude of mu, and the greater the friction coefficient of the membrane phase gamma, the smaller the magnitude of mu. (4) A large I or a large a leads to a small magnitude of mu. (5) The greater the ratio (permittivity of solution/permittivity of membrane phase), the smaller the magnitude of mu. (6) For a large gamma, magnitude of mu decreases with the thickness of membrane d under the condition of constant amount of fixed charges. However, if gamma is sufficiently small, the variation of magnitude of mu as a function of d exhibits a maximum. The classic result of Smoluchowski for the electrophoretic mobility of a rigid particle can be recovered as a limiting case of the present model.
Journal of Theoretical Biology 10/1996; 182(2):137-45. · 2.21 Impact Factor
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ABSTRACT: The interaction between colloidal particles in a solution containing polymer molecules is examined theoretically. In particular, the sticking probability of colloidal particles, which plays a significant role in the determination of the collision efficiency of an unstable dispersed system, is analyzed. We found that the sticking probability is extremely sensitive to the variation in the Hamaker constant of a colloidal particle. In the conventional analysis of the collision efficiency in polymer-induced flocculation, it is assumed that the adsorption of polymer is relatively fast than the collision of colloidal particles. Since the adsorption of polymer will significantly affect the properties of the surface of a colloidal particle, this assumption may lead to an appreciable deviation in the prediction of collision efficiency.
Colloid and Polymer Science 02/1995; 273(3):271-278. · 2.33 Impact Factor
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ABSTRACT: A problem often overlooked in the study of the repair of radiation-induced DNA double-strand breads (DSBs) is the question of what the status of a regular site is in the DNA duplex immediately after a radiation treatment. Here, we suggest a mixed repair mechanism which consists of a gradual process and an instantaneous process. A comparison of the present kinetic model with those which have appeared in the literature shows that the former is a generalization of the latter. We have shown that different repair mechanisms may lead to equivalent mathematical representations. Therefore, care must be taken in interpreting the repair mechanism on the basis of the experimentally observed transient number of DSBs.
Proceedings of the National Science Council, Republic of China. Part B, Life sciences 03/1991; 15(1):28-31.
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ABSTRACT: A three-state stochastic model is described for the repair of radiation-induced double-strand breaks (DSBs) in DNA. If irradiated, a site or region in DNA is assumed to be in a potentially damaged state; this site may either become permanently damaged or be repaired after a certain period of time. The result of the analysis of the available experimental data reveals that the present two-parameter model is capable of interpreting the rapid decrease in the number of DSBs in the initial period, which cannot be predicted by previously proposed models. The stochastic analysis yields not only the temporal variation of the mean of the number of DSBs but also its variance, and therefore is a generalization of the conventional deterministic models.
Mathematical Biosciences 07/1990; 100(1):21-31. · 1.54 Impact Factor
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ABSTRACT: The repair of radiation-induced DNA double-strand breaks (DSBs) is analyzed kinetically. It is assumed that a fraction of the damaged sites in the DNA duplex are irreparable. The kinetic model takes the effect of radiation dose into account. The analysis of the available experimental data reveals that, although the number of irreparable DSBs is a quadratic function of radiation dose, the normalized number of irreparable DSBs correlates linearly with this variable.
Radiation Research 07/1990; 122(3):333-6. · 2.68 Impact Factor
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ABSTRACT: The growth of a tumor is described by a nonlinear stochastic representation. A systematic approach based on Taylor series expansion is adopted to solve the nonlinear master equation governing the variation of tumor weight as a function of time. The analysis of the available experimental data reveals that the growth rate of a tumor has a power law dependence on its weight.
Zhonghua Minguo wei sheng wu ji mian yi xue za zhi = Chinese journal of microbiology and immunology 03/1990; 23(1):68-74.
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Journal of Theoretical Biology 03/1989; 136(3):357-9. · 2.21 Impact Factor
