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The drug apparent permeability (P app) is calculated by normalizing the drug flux (j) over the initial concentration of the API in the donor compartment (c 0) as: Equation 2: = / Dimensionally, the P app represents a velocity, and it is normally expressed in cm/sec. The highest is the permeability, the highest is expected to be the ...
A practical unit for permeability is the darcy (d), or more commonly the millidarcy (md) (1 d ≈ 10 −12 m 2). The name honors the French Engineer Henry Darcy who first described the flow of water through sand filters for potable water supply. Permeability values for most materials commonly range typically from a fraction to several thousand ...
This is a very important mechanism in biology where fluids inside a blood vessel need to be regulated and controlled. Permeation can occur through most materials including metals, ceramics and polymers. However, the permeability of metals is much lower than that of ceramics and polymers due to their crystal structure and porosity.
This explains the duality in Darcy's law as a governing equation and a defining equation for absolute permeability. The non-linearity of the material derivative in balance equations in general, and the complexities of Cauchy's momentum equation and Navier-Stokes equation makes the basic equations in classical mechanics exposed to establishing ...
Permeability is a measure of how easily an ion can cross the membrane. It is normally measured as the (electrical) conductance and the unit, siemens, corresponds to 1 C·s −1 ·V −1, that is one coulomb per second per volt of potential. So, in a resting membrane, while the driving force for potassium is low, its permeability is very high.
In cellular biology, membrane transport refers to the collection of mechanisms that regulate the passage of solutes such as ions and small molecules through biological membranes, which are lipid bilayers that contain proteins embedded in them. The regulation of passage through the membrane is due to selective membrane permeability – a ...
Differences in vascular permeability between normal tissue and a tumor. Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules (drugs, nutrients, water, ions) or even whole cells (lymphocytes on their way to the site of inflammation) in and out of the vessel.
Permeability (earth sciences), a measure of the ability of a material (such as rocks) to transmit fluids Relative permeability, in multiphase flow in porous media; Permeability (foundry sand), a test of the venting characteristics of a rammed foundry sand; Hydraulic conductivity, the permeability of soil for water