Biomedical subjects
Publications and source records attributed to John Canning.
The inscription of type IIA fiber Bragg gratings in standard boron-codoped germanosilicate fiber has been demonstrated to show marked differences from that reported in the literature. These gratings were subjected to high temperatures, and their decay behavior was evaluated. Gratings resistant to heat up to 800 degrees C for a moderate length of time are demonstrated.
A novel grating-writing interferometer is demonstrated. This interferometer is compact, stable, and tunable well over 1000 nm and does not suffer from the inherent path-length differences that are present in other methods. It allows for high-quality gratings to be inscribed by preventing light from unwanted orders from affecting the fringe pattern. This technique is used to introduce a novel method of apodization based on removing the Fresnel end reflections in a grating. The experimental evidence proves the concept and shows that the technique is potentially useful for Bragg-grating inscription.
Poor healing of high-energy fractures is often associated with severe muscle damage. This may be partly due to the production, by the injured muscle, of inflammatory cytokines that somehow misdirect bone healing. In order to investigate this question, an animal model was established which embodies a controlled degree of muscle injury with a dose response to the energy absorbed, that can be characterised histologically. Using a custom crush jig, 60 CFLP mice had either 100 or 200 g masses dropped from a fixed height onto the quadriceps muscle, with mechanical measurement of the impact. Energy of impact was reliably and significantly different between the small and large impact conditions, though there was more variability when the large mass was used. Animals were sacrificed at day 2, 4, 8, 16, and 24 post-injury. Muscle histomorphometry at all time points and immunohistochemistry for IL-1beta, IL-6, and TNF-alpha up to day 8 were used as measures of muscle damage, inflammation and repair. Histological sections were analysed into areas of normal muscle fibres, damaged/regenerating muscle fibres and fibrous/inflammatory infiltrate. Early histological response was similar between the two groups; the large crush group displayed significantly greater areas of inflammatory infiltrate and damaged muscle at the later time points after day 8. In the large crush group, IL-1beta and IL-6 expression were significantly higher at day 2 and TNF-alpha was higher at day 8 when compared to the small crush group. The experiment demonstrated that more severe injury to muscle was reliably followed by increased inflammatory cytokine production and a greater degree of inflammation and fibrosis. Increased production of inflammatory cytokines such as TNF-alpha and IL-1beta in the damaged muscles may activate macrophages and recruit fibroblasts, promote scar formation and lead to delayed union or non-union of the adjacent fracture(s).
The principle of an antisymmetric grating coupler was recently proposed theoretically as a planar waveguide add-drop multiplexer. It has the potential to enhance significantly the functionality of an add-drop multiplexer based on grating-assisted coupling. Here we realize the concept experimentally in an all-fiber geometry. We show that conventional devices exhibit two high-reflection bands. In contrast, the antisymmetric grating coupler has only a single reflection band, thereby dramatically improving its filtering characteristics.
The intrinsic 244-nm photosensitivity of boron-codoped germanosilicate optical fibers is enhanced by 355-nm hypersensitization. Hypersensitization through standard polymer coating is also demonstrated.