Component-resolved bleaching correlation between OSL and IRSL signals in various geological materials.

The primary aim of the present study includes establishing a qualitative as well as quantitative correlation between OSL and IRSL signals in various materials of geological origin, by investigating the influence of the IR stimulation to the OSL signal. The materials which are the subject of the present study include one K-feldspar belonging to the group of microcline, two different grain size fractions of Durango apatite at the edge of the nano-scale and gypsum. A two-step stimulation protocol was applied, including an exposure of the irradiated sample to infrared stimulation for various time and a subsequent continuous wave OSL using blue light. In the framework of a component-resolved analysis, the IRSL decay curves were fitted using analytical equations describing the localized tunneling recombination model; the subsequent OSL decay curves were also fitted using a linear superposition of analytical expressions describing both delocalized and localized recombination processes. The selection of number and type of components in the latter case is also elaborated, based on the physical meaningfulness of the de-convolution results.

Bioactivity characterization of 45S5 bioglass using TL, OSL and EPR: Comparison with the case of 58S sol-gel bioactive glass.

The current work exploits the effective application of thermoluminescence (TL), optically stimulated luminescence (OSL) and the possibility of applying Electron Paramagnetic Resonance (EPR) for the discrimination between different bioactive responses in the case of the 45S5 bioactive glass (SiO2 45, Na2O 24.5, CaO 24.5, P2O5 6 in wt%), which was synthesized through melting process. These techniques are suggested mainly due to their low spectroscopic detection thresholds. The original 45S5 in grain size range of 20-40µm was immersed in the Simulated Body Fluid (SBF) for various different immersion times ranging over one week. In this work the 110°C TL peak, a specific OSL component and the EPR signal at g=2.013 ascribed to oxygen hole center (OHC) are used due to their sensitivity to the different bioactive responses. For all luminescence and EPR components, the intensity plot versus immersion time yields sharp discontinuities, resulting in effective probes regarding the timescale for both the beginning as well as the end of the procedure of the crystalline HCAp formation respectively. On the contrary to the smooth decreasing pattern of both luminescence entities, the peak to peak amplitude of the EPR signal indicates an initial increase for the initial 16min of immersion, followed by a further decrease throughout the immersion time duration. The discontinuities monitored for both sensitivity of TL, OSL and EPR, in conjunction with the discontinuities monitored for the sensitization of TL and OSL, when plotted versus immersion time, provide an individual time scale for each one of the chemical reactions involved in the five steps of the aforementioned procedure. According to the authors' best knowledge, scarce characterization techniques could provide this time scale frame, while it is the first time that such an application of OSL and EPR is attempted. Finally, the bioactive response of the 45S5 bioglass was compared with that of the 58S sol-gel bioactive glass, in terms of the timescale of these five stages required for the final formation of the HCAp. The techniques of luminescence and EPR which take advantage of trapped charges are proposed as alternative cheap and prompt effective techniques towards discrimination between different bioactive responses in bioactive glasses.

Calculation of radiation dose to the lens of the eye using Monte Carlo simulation.

The radiation dose to the lens of the eye of patients undergoing diagnostic and interventional radiological procedures of the lacrimal drainage system has been calculated using a Monte Carlo technique. The technique has also been suggested for the retrospective estimation of the lens dose: when applied to individual patients, good correlation is obtained. In such study, data is required for image acquisition frame numbers and fluoro on-time, mean exposure values for these parameters, and the ratio of lens-to-air dose (viz, the head factor, HF) derived for a standard adult head.

Lens of the eye: radiation dose in balloon dacryocystoplasty.

PURPOSE: To evaluate the absorbed radiation dose to the lens of the eye, which is the critical organ in the primary beam during fluoroscopically guided transluminal balloon dilation of the lacrimal drainage system (balloon dacryocystoplasty) for obstructive epiphora and to evaluate the possibility of deterministic radiation effect on the lens. MATERIALS AND METHODS: The radiation dose to the lens of the eye during balloon dacryocystoplasty (which includes pre- and postintervention dacryocystography) was measured in 10 consecutive patients by using thermoluminescent dosimeters on the lids of both eyes as close as possible to the lenses. A C-arm angiographic unit coupled with a digital imaging system was used, with similar exposure and geometric parameters in all cases. RESULTS: The mean radiation dose to the lens of the treated eye was 4.6 mGy +/- 2.2 (dose range, 1.9-9.1 mGy) and to that of the untreated eye was 38.5 mGy +/- 17.5 (dose range, 14.7-67.8 mGy). CONCLUSION: The lens of the untreated eye receives a higher dose than that of the treated eye because of its closer proximity to the x-ray tube in a lateral projection. In the lens, even the highest measured radiation dose (67.8 mGy) still was well below the deterministic threshold for lens opacity and cataract formation.