Isopycnic point

Centrifuge at 400 g for 30 min in a swing-out rotor. Cells distribute to their isopycnic points, creating bands representing normal, dead and apoptotic cells. 

A superposition of data is shown in fig. 9 for samples boiled 1 hour which contain 36 % by weight water. Here the region of the scattering maximun has been explored. In this case the isopycnic point was determined to correspond to a concentration of 25 % H20/75 % D20. 

Density. The difference in density between the two hquid phases in eqiiilibrium affects the countercurrent flow rates that can be achieved in extrac tion equipment as well as the coalescence rates. The density difference decreases to zero at a plait point, but in some systems it can become zero at an intermediate solute concentration (isopycnic, or twin-density tie line) and can invert the phases at higher concentrations. Differential types of extractors cannot cross such a solute concentration, but mixer-settlers can. 

As mentioned earlier, the physical properties of a liquid mixture near a UCST have many similarities to those of a (liquid + gas) mixture at the critical point. For example, the coefficient of expansion and the compressibility of the mixture become infinite at the UCST. If one has a solution with a composition near that of the UCEP, at a temperature above the UCST, and cools it, critical opalescence occurs. This is followed, upon further cooling, by a cloudy mixture that does not settle into two phases because the densities of the two liquids are the same at the UCEP. Further cooling results in a density difference and separation into two phases occurs. Examples are known of systems in which the densities of the two phases change in such a way that at a temperature well below the UCST. the solutions connected by the tie-line again have the same density.bb When this occurs, one of the phases separates into a shapeless mass or blob that remains suspended in the second phase. The tie-lines connecting these phases have been called isopycnics (constant density). Isopycnics usually occur only at a specific temperature. Either heating or cooling the mixture results in density differences between the two equilibrium phases, and separation into layers occurs. 

Isopycnal A fine on a chart or map that connects points of constant seawater density. 

Associated with the new cmin class of profiles, we would find steady-state methods such as isoelectric focusing, isopycnic sedimentation, and some related methods that have been proposed [14]. The unique ability of these methods to separate mixtures into many zones or bands is related to the fact that the minimum for each component is found at a different point in space. 

At this point, the variables C and u are now used to connote the average (macroscopic) tracer concentration and velocity, respectively, and the overbar is dropped for convenience. Implicit in this formulation is the belief that fundamentally Lagrangian (particle) dispersion can be modeled as a continuum Eulerian phenomenon in a fashion analogous to the Fickian formulation of molecular transport by Brownian motion. This is a useful fiction for simple modeling exercises, but must be used with caution (see the next section on isopycnal diffusion). 

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