Particle repulsion

In a qualitative way, colloids are stable when they are electrically charged (we will not consider here the stability of hydrophilic colloids - gelatine, starch, proteins, macromolecules, biocolloids - where stability may be enhanced by steric arrangements and the affinity of organic functional groups to water). In a physical model of colloid stability particle repulsion due to electrostatic interaction is counteracted by attraction due to van der Waal interaction. The repulsion energy depends on the surface potential and its decrease in the diffuse part of the double layer the decay of the potential with distance is a function of the ionic strength (Fig. 3.2c and Fig. 

Impregnating a basic colloidal suspension (pH = 12) on alumina does not induce proton liberation, thus the pH is constant (Fig. 13.25b). The system keeps its initial properties, i.e. negative charges for alumina support and PdO particles. Repulsive interactions are created between the alumina surface and the PdO particles so that the particles deposited on the support are redispersed, and finally isolated from each other. 

Guyot-Hermann, A.M., and Ringard, J., Disintegration mechanisms of tablets eontaining starches. Hypothesis about the particle-particle repulsive force. Drug Dev. Ind. Pharm., 7 155-177 (1981). 

The partition function of the quantum gas can then be constructed from the single-particle repulsion partition function, qTep and the contribution of attraction, Q ... 

Because of the complexities involved, the mechanism of action of super disintegrants is not well understood. Some of the proposed mechanisms include water wick-ing, swelling, deformation recovery, particle repulsion, and heat of wetting. Water uptake is a necessary... 

Fig. 18. Free energy curve for crystallization of an 864-particle repulsive LJ system. EXEDOS simulations at T = 1.14 solid line, predicted free energy profile by reweighing T = 1.14 data to T = 1.03 dashed line, and EXEDOS simulations at T = 1.03 dot-dot-dashed line. From Chopra et al. [33]...

By adsorption onto particles they may greatly affect colloidal interaction forces between those particles. Repulsive forces may provide long-term stability against aggregation attractive forces may allow the formation of continuous networks. 

Aggregating Particles. Repulsive colloidal interaction forces between particles hardly affect sedimentation, but the effect of attractive forces can be very strong. Aggregates naturally sediment faster than single particles. Fractal aggregates containing N particles tend to move faster than... 

The unknown latex sample is injected and the centrifuge spun in the absence of flow to provide for the establishment of the particle equilibrium distribution (relaxation period). The density of the carrier solution, is determined. The flow is started and a fractogram is collected. The elution positions for the resolved components are determined and their sizes calculated corresponding to the observed retentions (no calibrations needed). The adsorption complex between a protein and one of the sample latices is formed. The above procedure is repeated using a buffer suitable for maintaining the coated particles in suspension and with an ionic strength such that particle repulsion is minimal during fractionation. The surface density of the adsorbed protein is calculated. 

In the full Hamiltonian the electron repulsion is exact , it is simply the sum of all the inter-particle repulsions. In the HF Hamiltonian this is replaced by Coulomb and exchange terms. The Coulomb term is simply the net average repulsion field due to all the electrons in the molecule and the exchange term removes the self-interaction term included in this average sum plus some further small corrections. 

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