STATEMENT OF PROBLEM As a physical property, wear resistance of the materials used in the fabrication of orthodontic retainers play a significant role in the stability and long term use of the appliances. OBJECTIVES To evaluate the wear resistance of two commonly used materials for orthodontic retainers: Acropars OP, i.e. a polymethyl methacrylate based material, and 3A-GS060, i.e. a polyethy...

We have prepared films of polymethyl .methacrylate in which fullerenes (a mixture of C,, and C,,) are uniformly embedded. By performing both degenerate four-wave mixing experiments and h-radiance-dependent transmission measurements with nanosecond laser pulses of 608nm wavelength, the third-order nonlinear optical susceptibility of these films is determined to be of the order of 10-l’ esu. This...

For revision knee surgery with uncontained tibial bone defects, the authors report the containment of compacted morsellized allograft using metal-wire mesh, followed by implantation of a cemented total knee prosthesis. This method is comparable to the "impaction grafting technique" described for revision hip surgery and could be an alternative to metal wedges, augmented components, custom-made ...

The efficiency of nonequilibrium electron trapping by capture centers in alkali halide crystals, quartz, and polymethyl-methacrylate exposed to an intense electron beam with a beam current density of about 20 A/cm 2 is studied. The trapped charge is estimated from the amount of irradiation-induced electrification of high-resistivity materials. It is shown that traps having captured thermalized ...

We demonstrated the fabrication of Fresnel zone plates with a 75 nm minimum feature size and circular gratings with a 20 nm minimum linewidth in polymethyl methacrylate using nanoimprint lithography, and in metals by means of a lift-off technique. Observation of sharp Moiré patterns indicated the high fidelity of nanoimprint lithography in pattern duplication. Our results showed that nanoimprin...