Evaluation of the effects of stress concentrations on plates using granular micromechanics

This work is dedicated to the study of the effect of stress concentrations in plates induced by notches and holes using a Granular Micromechanics (GM) model. To this end, three structural configurations were analyzed: an intact plate, a plate with a central circular hole, and a plate with two notches. For comparison of the mechanical response of these plates, the radii of the hole and the notches are taken the same. The material behavior of the plates is described through the multiscale GM constitutive law. The equations of this model are formulated based on the mechanical properties of the grains, the grain-pair interactions and the relative movement of the grains. So the identification of the material parameters needs only the determination of the grains’ properties and grain-pair interactions. This micromechanics-based model has been implemented into the finite element code Abaqus/Explicit through a Vectorized User MATerial (VUMAT) subroutine. The model is applied to study the plates under uniaxial and biaxial loadings. This study aims to assess the pertinence of applying the GM model to structural analysis and show the influence of the two geometrical imperfections on the overall behavior of the structure. It has been found that the model can describe the behavior of plates under tension and compression loadings. Moreover, the effects of a hole and notches on the behavior and failure of the granular-made plates are captured

The use of nano polymeric self-assemblies based on novel amphiphilic polymers for oral hydrophobic drug delivery

To investigate the use of nano self-assemblies formed by polyallylamine (PAA) modified with 5 or 10% mole fluorenylmethoxy carbonyl (Fmoc(5)/(10)), dimethylamino-1-naphthalenesulfonyl (Dansyl(5)/(10)) and 5% mole cholesteryl group (Ch(5)) for oral hydrophobic drug delivery. Propofol, griseofulvin and prednisolone were loaded into amphiphilic PAAs. Particle size and morphology of drug-loaded self-assemblies were determined using photon correlation spectroscopy and transmission electron microscopy. Solubilising capacity, in vitro drug release and formulation stability were analysed by HPLC, and in vitro biocompatibility studies (haemolysis and cytotoxicity) were carried out on bovine erythrocytes and Caco-2 cells, respectively. Dansyl(10) and Ch(5) griseofulvin formulations were administered intra-gastrically to rats, and drug plasma levels were analysed by HPLC. Drug-encapsulated self-assemblies typically have hydrodynamic size of 300-400 nm. Dansyl(10) exhibited universal drug solubiliser property and had significantly improved prednisolone, griseofulvin and propofol solubility by 145, 557 and 224-fold, respectively. Fmoc polymers resulted in modest drug solubility improvement. These polymers were non-haemolytic, did not enhance cytotoxicity compared to unmodified PAA, and demonstrated significant increase in griseofulvin plasma concentration compared to griseofulvin in water after oral administration. Ch(5) and Dansyl(10) showed promising potential as nano-carriers for oral hydrophobic drug deliver