total concentrations of mineral elements in soil bear little relation to their availability for plants. the dgt (diffusive gradients in thin-films) technique has been found to be a good predictor of trace metals, micronutrients, phosphorous and potassium bio-availability and uptake. in the dgt technique, elements are accumulated on a binding gel after their diffusive transport through a hydroge...

Uphill diffusion, the diffusion of a component up its own concentration gradient, has often been observed in experimental studies of diffusion i synthetic multicomponent systems and natural silicate melts. To apply experimental data to natural processes, it is necessary toquantify this effect. A modified effective binary diffusion model is developed in this paper. The diffusive flux of a compon...

BACKGROUND Fluid and sodium balance is important for the success of long-term peritoneal dialysis. Convective transport is the major determinant for sodium removal during peritoneal dialysis using conventional dialysis solutions. However, recent studies showed that lower sodium concentration in dialysate could significantly increase sodium removal by increasing the diffusion gradient, thereby i...

Abstract Cancer invasion and metastasis are influenced by a plethora of biochemical processes involve many mechanisms, among which chemotaxis haptotaxis two the main mechanisms directing migration cancer cells Chaplain Lolas (2005). Evidence has been found that release complex enzymes such as urokinase-type plasminogen activator (uPA), degrade surrounding extracellular matrix (ECM), thereby all...

Cellular responses to chemical cues are at the core of a myriad of fundamental biological processes ranging from embryonic development to cancer metastasis. Most of these biological processes are also influenced by mechanical cues such as the stiffness of the extracellular matrix. How a biological function is influenced by a synergy between chemical concentration and extracellular matrix stiffn...

A sequential implicit numerical scheme is proposed for a system of partial differential equations defining the transport of heat and mass in the channel flow of a variable-viscosity fluid. By adopting the backward difference scheme for time derivative and the central difference scheme for the spatial derivatives, an implicit finite difference scheme is formulated. The variable-coefficient diffu...

The double-diffusive convection in a compressible couple-stress fluid layer heated and soluted from below through porous medium is considered in the presence of a uniform vertical magnetic field. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, stable solute gradient, magnetic field, and coup...

Two-dimensional unsteady incompressible flows in which the potential vorticity (PV) plays a key role are examined in this study, through the development of the evolution equation for the PV gradient. For the case where the PV is conserved, precise statements concerning topologyconservation are presented. While establishing some intuitively well-known results (the numbers of eddies and saddles i...

We study qualitative properties of non-negative solutions to the Cauchy problem for the fast diffusion equation with gradient absorption ∂tu−∆pu+ |∇u| q = 0 in (0,∞)× R , where N ≥ 1, p ∈ (1, 2), and q > 0. Based on gradient estimates for the solutions, we classify the behavior of the solutions for large times, obtaining either positivity as t → ∞ for q > p − N/(N + 1), optimal decay estimates ...

This paper describes a method to create stable chemical gradients without requiring fluid flow. The absence of fluid flow makes this device amenable to cell signaling applications where soluble factors can impact cell behavior. This device consists of a membrane-covered source region and a large volume sink region connected by a microfluidic channel. The high fluidic resistance of the membrane ...