diffusion coefficient

(redirected from Diffusion constant)
Also found in: Medical, Encyclopedia.

diffusion coefficient


diffusion constant

(General Physics) the rate at which a diffusing substance is transported between opposite faces of a unit cube of a system when there is unit concentration difference between them. Symbol: D Also called: diffusivity
Mentioned in ?
References in periodicals archive ?
One key drawback of this system is that the gold nanoparticles (~40 nm) increase the size and thus reduce the diffusion constant of the protein.
The values of intra-particle diffusion constant k id shown in Table-1 were attained from slopes of linear portions of plots.
The rate parameters were used to find the type of transport mechanism and diffusion constant. Conversely, the SR and rate constant ([k.sub.v]) values of the PHA gels varied randomly.
An extrapolation of the plot of quantity against time gives the time lag [t.sub.L] which is related to the diffusion constant by
Increasing vacancy concentration increases the diffusion constant and solubility of impurity up to [10.sup.20] [cm.sup.-3] [20-22].
where M(t) is the released drug amount at t, [M.sub.[infinity]] is the released drug amount after very large time intervals, tending to infinity, equal, in most cases, with the drug amount loaded into polymeric matrices, [K.sub.H] is the Higuchi diffusion constant, [K.sub.P] is the Korsmeyer-Peppas constant, an indicator of release rate, and n is an exponent that depends on the shape of the polymeric matrix and can indicate the drug release mechanism.
reported that atypical and malignant meningiomas tend to be markedly hyperintense on diffusion-weighted MR images and exhibit marked decreases in the diffusion constant ( D [sub]av) or apparent diffusion coefficient values when compared with normal brain parenchyma.[sup][17] Although atypical meningioma is diagnosed based on the histological criteria, if the radiological characteristics of a meningioma give the possible diagnosis of atypical meningioma before surgery, neurosurgeons should prepare to remove the tumor completely as possible as they can.
Similarly, the diffusion constant is related to the time evolution of the second moment of the distribution.
During homogenization process, effective diffusion constant and effective reaction rates as summarized in table- 2.
"Depending on the diffusion constant of an analyte, the system becomes equilibrated in a matter of minutes," says Wheeler, explaining that passive diffusion does all the work.
In true, it is an imaginary diffusion constant because there is no effective dislocation of matter in all directions (this is a single-particle description).
The purpose of this paper is to verify the unified form of DC conductivity and diffusion constant for translational-invariant hydrodynamics with a chemical potential, as a first step towards general formulae of transport coefficients of anisotropic and inhomogeneous hydrodynamics.

Full browser ?