Browsing by Author "Harland, CL"

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    The application of synchrotron radiation induced X-ray emission in the measurement of zinc and lead in Wistar rat ameloblasts
    (Elsevier, 2007-10) Arora, M; Kennedy, BJ; Ryan, CG; Boadle, RA; Walker, DM; Harland, CL; Lai, B; Cai, ZH; Vogt, S; Zoellner, H; Chan, SWY
    The development of analytical techniques for the measurement of trace elements in cellular compartments of developing teeth remains an important methodological issue in dental research. Recent advances in third generation synchrotron facilities have provided high brilliance X-ray sources that can be effectively used to study trace element distributions in small spatial regions with low detection limits. The present study describes for the first time the application of synchrotron radiation induced X-ray emission (SRIXE) in measuring the distribution of zinc and lead in the ameloblasts of developing Wistar rat teeth. Wistar rats were fed a standard rat diet, containing the normal dietary requirements of zinc, ad libitum and exposed to 100ppm of lead in drinking water. Resin embedded sections of first mandibular molars were analysed using a 13.3keV incident monochromatic X-ray beam focussed to a 0.2μm spot. Characteristic X-rays arising from the entire thickness of the sample were measured using an energy dispersive detector for quantitative analysis of elemental concentrations. The results showed that intranuclear concentrations of zinc were greater than levels in the cytoplasm. Furthermore, nuclear and cytoplasmic concentrations of zinc in the maturation stage (742±27 and 424±25ppm, respectively) were significantly higher than the zinc levels observed in the nucleus and cytoplasm of presecretory stage ameloblasts (132±10 and 109±10ppm, respectively) (p<0.05). A clear lead signal above the background was not detected in the ameloblasts and lead concentrations could only be reliably measured in the developing enamel. Overall, SRIXE was an effective method of studying the spatial distribution of zinc in the cells of developing teeth and offered a unique combination of sub-micron spatial resolution and parts-per-million detection limits (0.8–1 and 0.6–1ppm for zinc and lead, respectively). © 2007, Elsevier Ltd.
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    Exchange bias in a columnar nanocrystalline Ni80Fe20/CoO thin film
    (The American Physical Society, 2007-12-28) van Lierop, J; Southern, BW; Lin, KW; Guo, ZY; Harland, CL; Rosenberg, RA; Freeland, JW
    The effects of interfacial coupling at the boundary of ferromagnetic and antiferromagnetic components in a nanoscale columnar-structured thin film of Ni80Fe20/CoO have been examined. Field-cooling the film results in very different temperature dependences of the enhanced coercivity and exchange-bias shift of the hysteresis loop. The exchange-bias temperature dependence is well described by thermal fluctuations of the interfacial spins while the coercivity temperature dependence indicates that single-domain-like columns are being coherently rotated by the thermal fluctuations of the interface spins. Furthermore, only a portion of the spins in the antiferromagnetic layer seem to be associated with the spin coupling that results in exchange bias. X-ray magnetic resonant scattering measurements show clearly the presence of canted Co interfacial moments that provide a local field which enables exchange bias at a significantly higher temperature than the onset of an enhanced coercivity. © 2007, American Physical Society