In single phase flow of a passive tracer through heterogeneous porous media, a mixing layer develops between the tagged and untagged regions of the fluid. The mixing region expands as the time evolves. We have developed a multilength scale theory for the growth of the mixing region induced by a general random velocity field (multi-fractal field). The theory relates the statistics of the mixing ...

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We describe methods for the measurement of translational diffusion in very large static magnetic field gradients by NMR. The techniques use a "hole-burning" sequence that, with the use of fringe field gradients of 42 T/m, can image diffusion along one dimension on a submicron scale. Two varieties of this method are demonstrated, including a particularly efficient mode called the "hole-comb," in...

Purpose: To evaluate the mechanism of drug release of a slightly soluble drug (theophylline) from nanocomposite of zeolite (ZLT) or hydrotalcite (HTC) used as drug carrier. Methods: Nanocomposite was prepared with dispersion of either ZLT or HTC as drug carrier and theophylline (THP) as drug in drug to clay ratios of 1:2, 3:4 and 1:1. The formulations were characterized for drug release and loa...

Analysis of diffusion in a complex environment shows that the conventional diffusion equation based on Fick’s law fails to model the anomalous character of the diffusive mass transport observed in the field and laboratory experiments. New mathematical models of diffusive transport, different from Fick’s law, were proposed and validated in literature. In the present paper the examples of the equ...

Single-file diffusion, prevalent in many processes, refers to the restricted motion of interacting particles in narrow micropores with the mutual passage excluded. A single-filing system was developed by confining colloidal spheres in one-dimensional circular channels of micrometer scale. Optical video microscopy study shows evidence that the particle self-diffusion is non-Fickian for long peri...

Desorption of saturated polymers can be inhibited if a nearly dry (glassy) skin with a low diffusion coefficient forms at the exposed surface. In addition, trapping skinning can occur, where an increase in the force driving the desorption decreases the accumulated flux desorbed. The dynamics of such systems cannot be described by the simple Fickian diffusion equation. The mathematical model pre...

The World Health Organization (WHO) has reported that globally 235 million people suffer from chronic and other inflammatory diseases. The short half-lives of nonsteroidal anti-inflammatory drugs (NSAIDs) and their notoriety in causing gastrointestinal discomforts, warrants these drugs to be released in a controlled and sustained manner. Although polymeric particles have been widely used for dr...