Colloids plasma

Table 9.3. Some colloidal plasma volume expanders currently in therapeutic use. In addition to these, albumin and plasma protein fraction may also be used...

Alternatively, colloidal plasma expanders (Table 9.3) are used. When administered at appropriate concentrations, they exert an osmotic pressure similar to that of plasma protein, hence vascular volume and blood pressure are maintained. The major disadvantages of colloidal therapy include its relatively high cost, and the risk of prompting a hypersensitivity reaction. Determined elforts to develop blood substitutes were initiated in 1985 by the US military, concerned about the issue of blood supply to future battlefields. 

Apart from colloidal plasma expanders crystalloid (electrolyte) fluids are used in certain clinical conditions. 

Laxenaire MC, Charpentier C, Feldman L. Reactions anaphylactoides aux substituts colloidaux du plasma incidence, facteurs de risque, mecanismes. Enquete prospective multicentrique frangaise. Groupe franqais d Etude de la Tolerance des Substituts Plasmatiques. [Anaphylactoid reactions to colloid plasma substitutes incidence, risk factors, mechanisms. A French multicenter prospective study.] Ann Fr Anesth Reanim 1994 13(3) 301-10. 

Starch derivatives are relatively safer in terms of adverse reactions than other colloid plasma substitutes, but there is an incidence of anaphylactic reactions of 4-6 per million. 

The simplest approach conventionally employed to describe the grain screening in colloidal plasmas is the Debye-Hiickel (DH) approximation, or, its modification for the case of the grain of finite size, the DLVO theory [6,7], The DH approximation represents the version of Poisson-Boltzmann (PB) approach linearized with respect to the effective potential based on the assumption that the system is in the state of thermodynamical equilibrium. The DH theory yields the effective interparticle interaction in the form of the so-called Yukawa potential which constitutes the basis for the Yukawa model. 

Extensive molecular dynamics and Monte Carlo (MC) computer simulations performed for the Yukawa system (YS) [8-10] indicate that the latter provides a possibility for qualitative explanation of formation of condensed state in colloidal plasmas. However, it is clear that the accurate description of grain screening in colloidal plasmas requires more accurate approaches. Let us point out some important issues which should be first of all taken into account. 

It is clear that the above phenomenon of nonlinear screening is of importance for structural properties of colloidal plasmas. Its effect on the phase diagram for charged colloidal suspension can be illustrated on the basis of the model of effective intergrain forces in the following way. 

As mentioned above, the basic reference systems of colloidal plasmas based on the notion of effective interaction is the Yukawa system with the interparticle effective potential given by... 

Figure 3. Melting curves for colloidal plasmas in Z — A plane. Solid line v 5 10-2 long dashes v = 5 10 3 short dashes v 5 10 4. Nonlinear screening effects in shifting the melting curves to higher values of asymmetry Z at small packing fractions.

A more accurate description of the structure of colloidal plasmas can be obtained by means of MC computer simulations based on the microscopic model of asymmetric two-component plasmas (TCP). As shown above, the nonlinear grain screening obtained within PB theory has the direct analogue in the MC simulations with the microscopic description of plasma background, the phenomenon of plasma condensation near grain surface. This suggests that the above phenomenon should manifest itself in MC simulations of asymmetric two-component plasmas affecting its structural properties as well. 

Thus, we see that the properties of screening of high-Z impurities in colloidal plasmas may considerably vary depending on the physical processes in the plasma background. 

D yachkov, L. G. 2005a. Screening of macroions in colloidal plasmas Accurate analytical solution of the Poisson-Boltzmann equation. Physics Letters A 340, no. 5-6 440-448. 

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