{{Short description, A gradient in the rates of diffusion of multiple groups of molecules through a medium or substrate
A diffusion gradient is a
gradient
In vector calculus, the gradient of a scalar-valued differentiable function f of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p gives the direction and the rate of fastest increase. The g ...
in the rates of
diffusion
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...
of multiple groups of
molecule
A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
s through a medium or
substrate
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (aquatic environment), the earthy material that exi ...
. The groups of molecules may constitute multiple substances, portions of the same substance that have different temperatures, or other differentiable groupings. The analysis of diffusion gradients has applications in many sciences and technologies, as described for the following contexts:
*
Double diffusive convection, in which density differences, often reflecting temperature differences, affect fluid flows
*
Diffusion MRI
Diffusion-weighted magnetic resonance imaging (DWI or DW-MRI) is the use of specific MRI sequences as well as software that generates images from the resulting data that uses the diffusion of water molecules to generate contrast (vision), contrast ...
, which visualizes tissues on the basis of diffusion gradients of various molecules, especially water molecules
*
Immunodiffusion, which can use diffusion rate differentials to separate multiple immune complex species
Broad-concept articles
Diffusion