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A laboratory ultracentrifuge. In chemistry, a Svedberg unit or svedberg (symbol S, sometimes Sv [a]) is a non-SI metric unit for sedimentation coefficients.The Svedberg unit offers a measure of a particle's size indirectly based on its sedimentation rate under acceleration (i.e. how fast a particle of given size and shape settles out of suspension). [1]
The sedimentation coefficient is typically dependent on the concentration of the solute (i.e. a macromolecular solute such as a protein). Despite 80+ years of study, there is not yet a consensus on the way to perfectly model this relationship while also taking into account all possible non-ideal terms to account for the diverse possible sizes, shapes, and densities of molecular solutes. [2]
The critical velocity for deposition, on the other hand, depends on the settling velocity, and that decreases with decreasing grainsize. The Hjulström curve shows that sand particles of a size around 0.1 mm require the lowest stream velocity to erode. The curve was expanded by Åke Sundborg in 1956.
Sedimentation depends on mass, shape, and partial specific volume of a macromolecule, as well as solvent density, rotor size and rate of rotation. The sedimentation velocity can be monitored during the experiment to calculate molecular weight. Values of sedimentation coefficient (S) can be calculated. Large values of S (faster sedimentation ...
The particles' settling velocity in centrifugation is a function of their size and shape, centrifugal acceleration, the volume fraction of solids present, the density difference between the particle and the liquid, and the viscosity. The most common application is the separation of solid from highly concentrated suspensions, which is used in ...
Sedimentation is the deposition of sediments. [1] It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity , centrifugal acceleration , or ...
Sedimentation equilibrium in a suspension of different particles, such as molecules, exists when the rate of transport of each material in any one direction due to sedimentation equals the rate of transport in the opposite direction due to diffusion. Sedimentation is due to an external force, such as gravity or centrifugal force in a centrifuge.
where = / has units of velocity and is called the Darcy velocity (or the specific discharge, filtration velocity, or superficial velocity). The pore or interstitial velocity v p x {\displaystyle v_{px}} is the average velocity of fluid molecules in the pores; it is related to the Darcy velocity and the porosity n {\displaystyle n} through the ...