Deshan Liu

Anisotropic indentation morphology and hardness of natural ivory

Abstract An investigation of the orientation dependence of indentation morphology and microhardness is reported for natural ivory samples. Indentations exhibit rather different behavior in the three orthogonal planes related to the cylindrical geometry of the tusk, i.e., in the transverse, radial and circumferential planes. For instance, under a load of 50 g, the hardness value in the circumferential plane is about 25% larger than that in the radial plane. This mechanical property may be explained in terms of the special microarchitecture of the hydroxyapatite-like crystals and the collagen fibers in this biological tissue.

Immobilization of aminoglycosidic aminocyclitols antibiotic onto soap-free poly(MMA-EA-AA) latex particles

Monodispersed soap-free poly(MMA-EA-AA) latex particles with surface carboxyl groups were synthesized by emulsion polymerization of methyl methacrylate (MMA), ethyl acrylate (EA) and acrylic acid (AA) in aqueous medium, and streptomycin sulfate (SMS) was immobilized onto these particles using three different methods. A model experiment was designed to test the feasibility of the reaction between the carboxyl groups of polymer and the amino groups of the medicine. The covalent coupling between the latex particles and the medicine was confirmed by XPS. Results showed that the medicine molecules were located on the particle surface after immobilization, and the coupling efficiency of SMS in pre-adsorption method was higher than that in direct method. The highest coupling efficiency of this medicine was achieved using the spacer-arm method. It was demonstrated that the immobilized medicine had similar antimicrobial activity as the free form using Escherichia coli as an evaluating organism.