Ghost particle method

The excess chemiccil potential is thus determined from the average of exp[—lT (r )/fe In ensembles other than the canonical ensemble the expressions for the excess chem potential are slightly different. The ghost particle does not remain in the system and the system is unaffected by the procedure. To achieve statistically significant results m Widom insertion moves may be required. However, practical difficulties are encounte when applying the Widom insertion method to dense fluids and/or to systems contain molecules, because the proportion of insertions that give rise to low values of y f, dramatically. This is because it is difficult to find a hole of the appropriate size and sha... 

At liquid-like densities, the configurational-bias ghost particle approach is reliable only for chain molecules of intermediate length [71]. This limitation can be partially overcome by applying other techniques, such as the method of expanded ensembles. 

Cells containing Hb-F are densely stained with erythrosln and cells with Hb-A appear as ghost cells Intermediate cells are stained more or less pink. Reticulocytes with Hb-A sometimes resemble Intermediate cells and may also show some Intracellular granulation. Inclusion bodies are visible In eluted cells as compact particles of differing sizes. Figure 10 gives some examples. The method Is Ideally suited to demonstrate the presence of newborn red cells In the maternal circulation. The method Is also widely used for the evaluation of the distribution of Hb-F within red cells mainly to differentiate between the HPFH condition and the 3 or 36 thalassemias. Evaluation of F cell smears In such cases Is difficult the term "equal distribution" usually Indicates the presence of Hb-F In each red cell but not necessarily In the same amount. 

A limited number of studies have been carried out on more concentrated systems using variations of the traditional electrophoretic method, e.g., the tracer and mass-transport methods. Reed and Morrison (35) have shown that, for d.c. fields, even in highly concentrated systems, the hydrodynamic and electrostatic interactions cancel one another when the double layers are thin, and the only effect which must be taken into account is the reverse flow of fluid displaced by the moving particles. Zukoski and Sav-ille (3 6), using red blood cells mixed with ghosts, have verified that this is so and that the d.c. mobility, of a concentrated system of volume fiaction d> is given by the simple relation ... 

One of the first approaches employed to impose a non-slip boundary condition at an external wall or at a moving object in a MFC solvent was to use ghost or wall particles [36,81]. In other mesoscale methods such as LB, no-slip conditions are modeled using the bounce-back rule the velocity of the particle is inverted from v to -V when it intersects a wall. For planar walls which coincide with the boundaries of the collision cells, the same procedure can be used in MFC. However, the walls will generally not coincide with, or even be parallel to, the cell walls. Furthermore, for small mean free paths, where a shift of the cell lattice is required to guarantee Galilean invariance, partially occupied boundary cells are unavoidable, even in the simplest flow geometries. 

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