Accounting for local capillary effects in two-phase flows with relaxed surface tension formulation in enriched finite elements

This paper introduces a numerical method able to deal with a general bi-fluid model integrating capillary actions. The method relies first on the precise computation of the surface tension force. Considering a mathematical transformation of the surface tension virtual work, the regularity required for the solution on the evolving curved interface is weakened, and the mechanical equilibrium of the triple line can be enforced as a natural condition. Consequently, contact angles of the liquid over the solid phase result naturally from this equilibrium. Second, for an exhaustive representation of capillary actions, pressure jumps across the interface must be accounted for. A pressure enrichment strategy is used to properly compute the discontinuities in both pressure and gradient fields. The resulting method is shown to predict nicely static contact angles for some test cases, and is evaluated on complex 3D cases.     

Osteoblast culture on bioerodible polymers: studies of initial cell adhesion and spread

The development of systems for the growth of osteoblasts on bioerodible polymeric matrices was explored. Three classes of bioerodible polymers were studied as possible matrix supports for osteoblast growth: the poly(anhydrides), poly(phosphazenes) and poly(lactic acid/glycolic acid) copolymers. Neonatal calvarial cells from Sprague–Dawley rats were seeded onto polymer disks at a density of 1 × 10⁴ cells/cm². Initial attachment and spreading, rate of growth and morphology were determined, and retention of osteoblast-like phenotype was assessed through measurements of alkaline phosphatase activity in the presence and absence of 1,25(OH)₂ vitamin D3. All results were considered relative to tissue culture polystyrene. Cells were found to attach to all polymers at 8 hr post-seeding. By 24 hr, cell numbers on all polymers were found to be decreased, except for poly(lactic acid/glycolic acid). Rat calvarial osteoblasts seeded on poly-(lactic acid/glycolic acid) reached confluency and retained their phenotype. Successful construction of viable osteoblast–bioerodible polymer composite materials, as presented in our study, may find their usefulness as grafts for atrophic non-unions of bone, for healing craniofacial and other defects and for use as prosthetic implants or coatings. Composite systems of osteoblast cultures may also find their usefulness in furthering our understanding of bone differentiation, maturation and metabolism in a matrix environment.