Yazar "Paraskevopoulos, Konstantinos M." seçeneğine göre listele

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    The 110°C Thermoluminescence peak as a probe in bioactivity study of the 58S sol-gel bioactive glass
    (Trans Tech Publications Ltd, 2011-11-06) Polymeris, George S.; Goudouri, Ourania Menti; Paraskevopoulos, Konstantinos M.; Kitis, George
    Results of the present study provide strong indications towards the effective application of the 110°C Thermoluminescence (TL) peak in discriminating between different bioactive responses for the case of the 58S bioactive glass. The in vitro bioactivity of this glass in the form of powder in SBF solution was tested for various immersion times, ranging between 0 and 6 days. This TL peak is ubiquitously present in all 58S samples, for all immersion times. The intensity of the 110°C TL peak was proven to be very sensitive to the different bioactive responses, indicating a strongly decreasing pattern with increasing immersion time in SBF, easily identifying thus the loss of silica. This loss is reflected to the decrease of the 110°C TL peak intensity, which appears to be fast even for the shorter immersion times. The 110°C TL glow peak intensity and sensitization could also be yielding a time scale regarding the beginning of some among the several stages included in the bioactivity sequence.
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    Thermoluminescence as a probe in bioactivity studies; the case of 58S sol-gel bioactive glass
    (IOP Publishing Ltd, 2011-10-05) Polymeris, George S.; Goudouri, Ourania Menti; Kontonasaki, Eleana; Paraskevopoulos, Konstantinos M.; Tsirliganis, Nestor C.; Kitis, George
    The formation of a carbonated hydroxyapatite (HCAp) layer on the surface of bioactive materials is the main reaction that takes place upon their immersion in physiological fluids. To date, all techniques used for the identification of this HCAp formation are rather time consuming and not well suited to detailed and rapid monitoring of changes in the bioactivity response of the material. The aim of this work is to explore the possibility of using thermoluminescence (TL) for the discrimination between different bioactive responses in the case of the 58S bioactive glass. Results provided strong indications that the 110 degrees C TL peak of quartz can be used effectively in the study of the bioactive behaviour of 58S bioactive glass, since it is unambiguously present in all samples and does not require deconvolution analysis. Furthermore, the intensity of the 110 degrees C TL peak is proven to be very sensitive to the different bioactive responses, identifying the loss of silica which takes place at the first stages of the sequence. The discontinuities of the 110 degrees C TL peak intensity plot versus immersion time at 8 and 1440 min provide experimental indications regarding the timescale for both the beginning of amorphous CaP formation as well as the end of crystalline hydroxyl-apatite formation respectively, while the spike in the sensitization of the 110 degrees C TL peak, which was observed for immersion times ranging between 20 and 40 min, could be an experimental feature indicating the beginning of the crystalline HCAp formation.
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    TL and OSL response of turquoise for dosimetric application
    (University of Aegean, 2010) Subedi, Bhagawan; Afouxenidis, Dimitrios; Polymeris, George S.; Tsirliganis, Nestor C.; Paraskevopoulos, Konstantinos M.; Kitis, George
    Turquoise is one of the amongst first gem stones used in jewelry and possessing cultural value since 2000 BC (at least). This work attempts characterize this stone scientifically using both thermally (TL) and optically stimulated luminescence (OSL) techniques. The experimental investigation included 1) the study of the natural TL and OSL signals, 2) the reproducibility of TL sensitivity over repeated irradiation and TL readout cycles, 3) dependence of sensitivity on annealing temperatures and 4) the TL and OSL dose response curves. The potential use of the TL and OSL techniques in determination of provenance, accidental dosimetry and probably to authenticity and dating purposes are then discussed.