No abstract

A study on the extrusion of microcellular polystyrene foams at different foaming temperatures was carried out using CO, as the foaming agent. The contraction flow in the extrusion die was simulated with FLUENT computational fluid dynamics code at two temperatures (1 50°C and 175°C) to predict pressure and temperature profiles in the die. The location of nucleation onset was determined based on the pressure profile and equilibrium solubility. The relative importance of pressure and temperature in determining the nucleation rate was compared using calculations based on classical homogeneous nucleation theory. Experimentally, the effects of die temperature (i.e., the foaming temperature) on the pressure profile in the die. cell size, cell density, and cell morphology were investigated at different screw rotation speeds (10 -30 rpm). Experimental results were compared with simulations to gain insight into the foaming process. Although the foaming temperature was found to be less significant than the pressure drop or the pressure drop rate in deciding the cell size and cell density, it affects the cell morphology dramatically. Open and closed cell structures can be generated by changing the foaming temperature. Microcellular foams of PS (with cell sizes smaller than 10 +m and cell densities greater than lo9 cells/cm3) are created experimentally when the die temperature is 160°C. the pressure drop through the die is greater than 16 MPa, and the pressure drop rate is higher than lo9 Pa/sec.

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This study investigates coaxial electrohydrodynamic spraying (electrospray for short) as a novel, rapid, real time and single-step method to produce oligodeoxynucleotide (ODN) encapsulated lipoplex nanoparticles for either intravenous injection or, potentially, pulmonary delivery. Using a coaxial needle setup, we produced G3139 (oblimerson sodium, or Genasense) encapsulated lipoplex nanoparticles, and investigated the effects of production parameters on nanoparticle size and structure. Careful control of production parameters yielded lipoplex nanoparticles 190 +/- 39 nm in diameter with unilamellar structure and 90 +/- 6% encapsulation efficiency of G3139. Both nontargeted and transferrin-targeted G3139 lipoplex nanoparticles were efficiently delivered to K562 cells and downregulated the bcl-2 protein expression by 34 +/- 6% and 57 +/- 3% respectively.