Particle size and shape effects in medical syringe needles: experiments and simulations for polymer microparticle injection.

Injection of polymeric microparticles is the final step in the drug delivery process. Experience has shown that blockage of the syringe mechanism can be a problem under certain conditions leading to poor control of the final product. Particle size and shape are postulated to be significant factors.

Cooperation versus competition in a mass emergency evacuation: a new laboratory simulation and a new theoretical model.

Virtual reality technology is argued to be suitable to the simulation study of mass evacuation behavior, because of the practical and ethical constraints in researching this field. This article describes three studies in which a new virtual reality paradigm was used, in which participants had to escape from a burning underground rail station. Study 1 was carried out in an immersion laboratory and demonstrated that collective identification in the crowd was enhanced by the (shared) threat embodied in emergency itself.

Formation of stable clusters in colloidal suspensions.

The experimental evidence and theoretical explanations of stable cluster formation in colloidal suspensions are reviewed. The clusters form in the intermediate range between a stable suspension built up by singlets and the irreversible coagulation or gelation of the suspension. The stable clusters develop as a result of a balance between competing short range attraction and long range repulsion between colloidal particles or due to reversible flocculation in the shallow secondary potential well.

Colloidal dynamics: influence of diffusion, inertia and colloidal forces on cluster formation.

Computer simulations of colloidal suspensions are discussed. The simulations are based on the Langevin equations, pairwise interaction between colloidal particles and take into account Brownian, hydrodynamic and colloidal forces. Comparison of two models, one taking into account inertial term in Langevin equation and another based on diffusional approximation proposed in [D.

Interaction forces between colloidal particles in liquid: theory and experiment.

The interaction forces acting between colloidal particles in suspensions play an important part in determining the properties of a variety of materials, the behaviour of a range of industrial and environmental processes. Below we briefly review the theories of the colloidal forces between particles and surfaces including London-van der Waals forces, electrical double layer forces, solvation forces, hydrophobic forces and steric forces. In the framework of Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, theoretical predictions of total interparticle interaction forces are discussed.