No abstract

Implants, consisting of smooth Inox cylinders, were cemented into the lower femur and upper tibia of nine sheep to study the distal migration of polyethylene particles. Some implants had a titanium-bead porous coat at the proximal end. These were of three types: In the first type, the porous coat was covered with hydroxyapatite to obtain a bony seal; the second type was prepared for a polymethylmethacrylate seal; in the third type, the porous zone was surrounded by a 2-mm-thick space to allow the formation of a fibrous seal. Small polyethylene particles were injected into the knees once a week during the third and fourth months after implantation. The animals were euthanized 2 months later. Major longitudinal sections of the implants and the surrounding bone were examined under a polarized light microscope. Birefringent particles were counted at the cement-bone and cement-implant interfaces. Osteolysis was not observed. None of the seals significantly decreased the migration of particles around the cemented part of the implants. Particles were observed in cement fissures and vacuoles. They migrated at both interfaces and in the bone itself. They were visible in marrow spaces between bone trabeculae.

We report on the electro-optic and dielectric properties of optical switching devices based on poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes sandwiching a polymer-dispersed liquid crystal (PDLC) layer. We demonstrate that the frequency dependence of the driving electric field on the optical properties of these devices allows the fabrication of flexible bandpass light modulators. The (PEDOT:PSS) electrodes are characterized using UV-Vis, scanning electron microscopy, Raman, conductive atomic force microscopy, and linear four probe technique. The PEDOT:PSS/PDLC-based displays exhibit similar electro-optical performances to those of ITO-based devices. In addition, it can function as a bandpass light modulator. This behavior resulted from depolarization fields (Maxwell–Wagner–Sillars effects) occurring (i) at the polymer/LC interface (low frequency) and (ii) between nanometer-sized conductive PEDOT-rich domains and poorly conductive PSS-rich areas present in the bulk and at the surface of the electrode (high frequency).