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Permeability (spatial And Transport Planning)}
Permeability, permeable, and semipermeable may refer to: Chemistry * Drug permeability *Semipermeable membrane, a membrane which will allow certain molecules or ions to pass through it by diffusion *Vascular permeability, the movement of fluids and molecules between the vascular and extravascular compartments *Permeation of a gas or vapor through a solid substance Earth and soil science *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 Electromagnetism *Permeability (electromagnetism), the degree of magnetization of a material in response to a magnetic field **Vacuum permeability, permeability of free space or magnetic constant, a physical constant, the value of magnetic permeability in a classical vacuum Veh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drug Permeability
In medicinal chemistry, Drug Permeability is an empirical parameter that indicates how quickly a chemical entity or an active pharmaceutical ingredient crosses a biological membrane or another biological barrier to become bioavailable in the body. Drug permeability, together with drug aqueous solubility are the two parameters that define the fate of the active ingredient after oral administration and ultimately define its bioavailability. When drug permeability is empirically measured ''in vitro'', it is generally called apparent permeability (Papp) as its absolute value varies according to the method selected for its measurement. Papp is measured ''in vitro'' utilizing cellular based barriers such as the Caco-2 model or utilizing artificial biomimetic barriers, such as the Parallel Artificial Membrane Permeation Assay (PAMPA) or the PermeaPad. All these methods are built on an acceptor compartment (from 0.2 up to several mL according to the method uses) where the drug solution is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semipermeable Membrane
Semipermeable membrane is a type of synthetic or biologic, polymeric membrane that allows certain molecules or ions to pass through it by osmosis. The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry. How the membrane is constructed to be selective in its permeability will determine the rate and the permeability. Many natural and synthetic materials which are rather thick are also semipermeable. One example of this is the thin film on the inside of an egg. Biological membranes are selectively permeable, with the passage of molecules controlled by facilitated diffusion, passive transport or active transport regulated by proteins embedded in the membrane. Biological membranes Phospholipid bilayer A phospholipid bilayer is an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vascular Permeability
Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the permeability of a blood vessel wall–in other words, the blood vessel wall's capacity to allow for the flow of small molecules (such as drugs, nutrients, water, or ions) or even whole cells (such as lymphocytes on their way to a site of inflammation) in and out of the vessel. Blood vessel walls are lined by a single layer of endothelial cells. The gaps between endothelial cells (cell junctions) are strictly regulated depending on the type and physiological state of the tissue. There are several techniques to measure vascular permeability to certain molecules. For instance, the cannulation of a single microvessel with a micropipette: the microvessel is perfused with a certain pressure, occluded downstream, and then the velocity of some cells will be related to the permeability.Michel, C. C., Mason, J. C., Curry, F. E. & Tooke, J. E. Development of Landis Techn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permeation
In physics and engineering, permeation (also called imbuing) is the penetration of a wikt:permeate#English, permeate (a fluid such as a liquid, gas, or vapor) through a solid. It is directly related to the concentration gradient of the permeate, a material's intrinsic permeability, and the materials' mass diffusivity. Permeation is modeled by equations such as Fick's laws of diffusion, and can be measured using tools such as a minipermeameter. Description The process of permeation involves the diffusion of molecules, called the permeant, through a membrane or interface. Permeation works through diffusion; the permeant will move from high concentration to low concentration across the interface. A material can be semipermeable, with the presence of a semipermeable membrane. Only molecules or ions with certain properties will be able to diffuse across such a membrane. This is a very important mechanism in biology where fluids inside a blood vessel need to be regulated and controlle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permeability (earth Sciences)
In fluid mechanics, materials science and Earth sciences, the permeability of porous media (often, a rock or soil) is a measure of the ability for fluids (gas or liquid) to flow through the media; it is commonly symbolized as ''k''. Fluids can more easily flow through a material with high permeability than one with low permeability. The permeability of a medium is related to the '' porosity'', but also to the shapes of the pores in the medium and their level of connectedness. Fluid flows can also be influenced in different lithological settings by brittle deformation of rocks in fault zones; the mechanisms by which this occurs are the subject of fault zone hydrogeology. Permeability is also affected by the pressure inside a material. The SI unit for permeability is the square metre (m2). A practical unit for permeability is the '' darcy'' (d), or more commonly the ''millidarcy'' (md) The name honors the French Engineer Henry Darcy who first described the flow of wat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relative Permeability
In multiphase flow in porous media, the relative permeability of a Phase (matter), phase is a dimensionless measure of the effective Permeability (Earth sciences), permeability of that phase. It is the ratio of the effective permeability of that phase to the absolute permeability. It can be viewed as an adaptation of Darcy's law to multiphase flow. Formulation For two-phase flow in porous media given steady-state conditions, we can write :q_i = -\frac \nabla P_i \qquad \text \quad i=1,2 where q_i is the Mass flux, flux, \nabla P_i is the pressure drop, \mu_i is the viscosity. The subscript i indicates that the parameters are for phase i. k_i is here the phase permeability (i.e., the effective permeability of phase i), as observed through the equation above. Relative permeability, k_, for phase i is then defined from k_i = k_k, as :k_ = k_i / k where k is the permeability of the porous medium in single-phase flow, i.e., the absolute permeability. Relative permeability must b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permeability (foundry Sand)
Permeability is a property of foundry sand with respect to how well the sand can vent, ''i.e.'' how well gases pass through the sand. And in other words, permeability is the property by which we can know the ability of material to transmit fluid/gases. The permeability is commonly tested to see if it is correct for the casting conditions. Affecting factors The grain size, shape and distribution of the foundry sand, the type and quantity of bonding materials, the density to which the sand is rammed, and the percentage of moisture used for tempering the sand are important factors in regulating the degree of permeability. Significance An increase in permeability usually indicates a more open structure in the rammed sand, and if the increase continues, it will lead to penetration-type defects and rough castings. A decrease in permeability indicates tighter packing and could lead to blows and pinholes. Testing procedure * On a prepared mould surface as a sample, permeability can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
