Samples were taken from the archeological excavation site, which was at the backs of the Side Antique Theatre. Samples were taken from under the base rock in this area. Polymineral fine grains were ...examined to determine the ages of the sediments. Samples gathered from the Side Antique Theatre were investigated through using the SAR method. Firstly, one part of the samples were evaluated by using conventional IRSL reading head model of (ELSEC-9010) which is infrared (880A-80 nm) stimulation source with Schott BG39 filter. The IRSL age dating with feldspar minerals, gives a number of overestimated or underestimated age values as a result. A new reading head was proposed with the following configuration attachments for overestimation of equivalent dose rates. Measurements were done with this newly designed red laser stimulating reading head which works with Elsec 9010 OSL age dating system. SAR measurements were performed by (650A-10 nm) red laser light source with two Schott BG3 filters. With usage of the new designed reading head; closer results were obtained in comparision with the Antique Theatrea2s expected age range. Fading rates were taken into consideration and these corrections were also handled for true age results.
Purpose
Diabetic retinopathy (DR) is the major cause of blindness in the working‐age population. With an increasing number of diabetic patients worldwide, automated screening tools become ...indispensable. Recent progress in machine learning and image analysis enables efficient automated screening.
Methods
DreamUp Vision uses state‐of the art technology based on deep‐learning. Our algorithm was trained on over 70,000 labeled retinal images. Images were graded by ophthalmologists as follows: 0 (no retinopathy), 1 (mild non proliferative DR), 2 (moderate non proliferative DR), 3 (severe non proliferative DR) and 4 (proliferative retinopathy). Each patient in the dataset is represented by two images of left and right eyes. Grading is done for each eye image separately. Our algorithm performs quick and reliable detection of anomalies in retinal images, diagnoses their stage of diabetic retinopathy and provides the location of the anomalies detected in the pictures. We consider a patient as referable if the DR stage is between 2 and 4, otherwise we consider the patient as non‐referable. We evaluate our model on over 10,000 fundus images from 5,000 patients taken from the Kaggle DR Detection Challenge dataset, provided by California Healthcare Foundation.
Results
Our algorithm achieves an area under the receiver operating characteristic curve AUROC of 0.946 with 96.2% sensitivity (95% CI: 95.8–96.5) and 66.6% specificity (95% CI: 65.7–67.5) for identifying referable DR on the Kaggle dataset.
Conclusions
The performances we have obtained enable a reliable automated DR screening. As the amount of available labeled data grows and given our technology's ability to learn from labeled images, we believe that significant performance improvement can be achieved. The same process can be applied to the detection of other eye diseases as well.
According to standard delocalized kinetic models of thermoluminescence (TL), when an irradiated sample is held at a high temperature T, the isothermal TL signal will decay with a characteristic ...thermal decay constant λ which depends strongly on the temperature T. This prediction of standard delocalized kinetic theory is investigated in this paper by studying two TL dosimeters, MgB4O7:Dy, Na and LiB4O7:Cu, In (hereafter MBO and LBO correspondingly). In the case of LBO it was found that the thermal decay constant λ of the main dosimetric TL peak follows exactly the predictions of standard delocalized kinetic theory. Furthermore, the thermal activation energy of the main peak evaluated by the isothermal decay method is in full agreement with values obtained from initial rise and glow curve fitting methods. However, in the case of MBO it was found that the thermal decay constant λ varies little with the isothermal decay temperature T. In order to explain these unusual results for MBO, the TL glow curves and isothermal decay curves were analyzed using analytical expressions derived recently from a radiative tunneling recombination model. Based on the different behavior of the two TL dosimeters, it is suggested that the isothermal decay of TL at high temperatures can be used to discriminate between radiative delocalized recombination and radiative localized recombination processes.
•Isothermal decay of TL in MgB4O7:Dy, Na and LiB4O7:Cu, In is studied.•The TL of LiB4O7:Cu, In is due to delocalized transitions.•The TL of MgB4O7:Dy, Na is due to tunneling transitions.•Recent TL expressions for delocalized and localized transitions are used to explain the results.
In the present work, pre-dosed α-quartz is investigated towards its effective applications in retrospective dosimetry and dating as a reference material. The purpose of the study is to find tentative ...correlations between Thermoluminescence (TL) (high temperature TL (HTTL) peaks), Optically Stimulated Luminescence (OSL) (both continuous wave (CW) and linear modulated (LM)) and Electron Paramagnetic Resonance (EPR). The present work indicates a triple correlation between the fast CW-OSL component and certain peaks of LM-OSL and TL signals, while all these luminescence entities are attributed to the EPR signal with g-value (Landé splitting factor) at 1.9975 called C2EPR. The present study provides experimental evidence that (i) one TL peak might be the source for more than two LM-OSL components and (ii) even two different TL peaks can contribute to the same OSL component. Furthermore, on the EPR signal, besides the well established Ge center, another un-identified component has been resolved.
The aim of this study is to determine the thermoluminescence (TL) kinetic parameters, including the activation energy (E), frequency factor (s) and order of kinetics (b), for the traps of silver and ...gadolinium co-doped lithium tetraborate (Li2B4O7:Ag,Gd) phosphor. Four different experimental techniques were applied, including Fractional Glow Technique (FGT), Computerized Glow Curve Deconvolution (CGCD), as well as both Isothermal TL (ITL) and Optically Stimulated Luminescence (OSL) measurements at various stimulation temperatures. The TL glow curve of the phosphor was determined to be composed of two single peaks with delocalization temperatures around 80 °C and 360 °C with a heating rate of 2 °C/s after 10 Gy beta dose. Moreover, a composite TL signal is observed within the temperature region between 110 °C and 320 °C. Both the deconvolution analysis as well as the FGT partially indicates that this composite signal consists of two overlapping TL glow peaks along with a satellite TL peak of suppressed intensity. The reusability of the phosphor was studied up to 20 experimental cycles using beta dose values of 0.5, 5 and 10 Gy to support the FGT procedure. The plot of activation energy vs measured temperature yielded a smooth continuum, with the presence of three not so prominent plateau regions. On the contrary, the CGCD analysis indicated the presence of five TL peaks with increasing activation energy values ranging between 0.63 and 1.56 eV. The ITL results indicate that for the constituents of the composite TL signal within 110 °C and 320 °C, the activation energy is less than 0.5 eV, while the corresponding OSL results of the same signal indicate an activation energy value of 0.83 eV. Based on the results of the present study, (a) the continuum shape of the E vs Tfin plot of the FGT analysis and (b) the behavior of the normalized ITL decay curves provide adequate arguments for the existence of a tunneling recombination pathway in the phosphor. The argumentation is also supported by recent related literature.
Although naturally occurring luminescence materials such as quartz and feldspars are generally used for radiation dosimetry and dating, natural borates may also stand as a promising material for ...dosimetry and dating. We report thermoluminescence (TL) and optically stimulated luminescence (OSL) of one of the most abundant boron minerals in Turkey namely, ulexite (NaCaB5O6(OH)6·5H2O). An X-ray diffraction (XRD) analysis confirmed that the sample has triclinic crystal structure and contains 40.55% of B, 5.92% of Na2O, 12.3% of CaO. A thermogravimetric analysis indicates two stages of dehydration within 60–160 °C, 160–250 °C and dehydroxylation within 260–580 °C. Analysis of TL glow curves using fractional glow and deconvolution reveal that there are four glow peaks at 154, 211, 273 and 327 °C in the glow curve of ulexite. All the glow peaks follow a non-first order kinetics. The activation energies of the traps are estimated from the fractional glow curves as 0.72, 0.93, 1.16 and 1.28 eV and that evaluated from the deconvolution analysis as 0.76, 0.83, 0.96 and 1.27 eV. The lifetimes of these traps are estimated within 1.55 days–3.6 × 104 years. The radiation dose responses of the TL peaks are supra-linear between 8 Gy and 1024 Gy. OSL decay curve of ulexite consists a fast, a medium and a slow component with recombination lifetimes of (0.63 ± 0.08), (7.51 ± 0.71), (93.49 ± 3.62) s respectively. The fast OSL component obeyed first order, whereas medium and slow components obeyed general order of kinetics. The dose response of the medium and slow OSL components showed a sub-linearity from 64 Gy to 4096 Gy whereas the fast component showed linear response between 8 and 4096 Gy.
•TL and OSL of ulexite collected from Kırka, Eskişehir, Turkey have been reported.•There are four electron traps of activation energy = 0.72, 0.93, 1.16 and 1.28 eV.•Lifetimes of the electron traps are estimated around 1.55 days to 3.6 × 104 years.•OSL curve of ulexite consists a fast (C1), medium (C2) and a slow (C3) component.•Dose response of C1 is linear (8‒4096Gy) but that of C2, C3 sub-linear (64‒4096Gy).
We report structural, chemical composition, thermal decomposition and stimulated luminescence properties of a colemanite-rich borate (Ca2B6O11•5H2O) mineral collected from Kırka, Eskişehir region of ...Turkey. X-ray diffraction shows that the colemanite phase has a monoclinic crystal structure. Further, Raman spectroscopic analysis reveals that the sample contains 45.83% of B and 17.93% of CaO. Thermogravimetric analysis indicates that there is removal of hydroxyl groups followed by explosive release of water from the sample at temperature below 200 °C. The sample produces thermoluminescence (TL) and optically stimulated luminescence (OSL) following beta irradiation. A TL glow curve measured at 1 °C/s consists of five glow peaks at ∼145, 175, 215, 267 and 322 °C. The activation energy associated with the peaks are ∼0.73, 0.77, 0.83, 0.90 and 1.19 eV respectively and the frequency factors are ∼106 ‒ 108 s−1. The lifetimes of the traps at room temperature are estimated to be ∼1.42 days to 2.33 × 104 years. The peaks at ∼175, 215 and 267 °C show supralinear dose response between 32 and 16000 Gy whereas the ones at ∼145 and 322 °C show supralinearity between 32 and 2048 Gy. Analysis of the OSL decay curve shows that the decay curve has a ‘fast’-, ‘medium’- and a ‘slow’ component. The dose response of the fast component is found to be linear within 2–4096 Gy and that of the medium- and slow components are found to be superlinear between 2 Gy and 4096 Gy.
•XRD, Raman, TGA, TL and OSL of a colemanite-rich borate mineral have been reported.•The sample contains 45.83% of B and 17.93% of CaO.•TL measured at 1 °C/s produces five glow peaks at ∼145, 175, 215, 267 and 322 °C.•There are five electron traps (E = 0.73, 0.77, 0.83, 0.90 and 1.19 eV).•OSL decay curve of the sample consists a fast-, medium- and slow-components.
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.
•Combined OSL and IRSL measurements on 4 different cases of naturally occurring minerals were performed.•IRSL depletes partially the fast OSL components.•The selection of number and type of components of both IRSL and OSL signals was justified.•Structural characterization is possible using de-convolution results.
Durango apatite is a material that exhibits very strong athermal fading (AF) of luminescence signal. In this study, the EPR signals of natural Durango apatite in various different grain dimensions ...(ball milled for various durations up to 48 h and microscale grain size) were studied. The obtained EPR signal at room temperature yielded three different components with g values 2.0534 (hole center), 2.0398 (hole center) and 1.9920 (electron center). These components were observed for the reference grain size fraction of 100–180 μm; however, prolonged ball milling erases the two hole centers. The behaviour of all obtained components was investigated by step annealing processes (a) between room temperature and 400 °C in steps of 25 °C for 5 min and (b) between 400 °C and 1100 °C, in steps of 100 °C for 1 h. The EPR component with g value 1.9918 was almost totally removed until 1100 °C, while those with g values 2.0534, 2.0398 were erased after annealing at 500 °C and 400 °C respectively. The fading of EPR components was investigated for each ball milling (BM) and microscale grain size independently, at different storage times between 0 and 1000 min. Based on the results of fading and step annealing studies, the EPR component with g value 2.0398 could be directly correlated to the main dosimetric TL trap, while the component with g value 1.9920 appears to be responsible for TA – OSL signal for microscale grain size apatite, corresponding thus to a very deep trap. The behaviour of remnant EPR signal versus storage time could be successfully described by equations based on quantum mechanical tunnelling mechanism.
•EPR signal of Durango apatite (grain size fraction of 100–180 μm) yields three different components at RT.•After ball milling, only one EPR component is monitored; the other two disappear.•EPR component with g = 1.9920 could be correlated to VDTs, as the origins of TA – OSL signal, based on thermal cleaning and athermal fading results.•EPR component with g = 2.0398 could be correlated to the main dosimetric TL trap.
A rapidly decaying curve shape, similar to the conventional optically stimulated luminescence (OSL) curve, is observed when thermally assisted (TA –) OSL signal from quartz is measured at a steady ...elevated temperature. In some cases, a peculiar shape consisting of one flat signal is yielded. The effects of thermal assistance and dose applied on the features of this peculiar type of curve were studied using quartz samples collected from Anatolia, Turkey. The results indicated the absence of the initial rapidly decaying part of the conventional OSL for this peculiar curve of TA-OSL for all stimulation temperature and dose ranges attributed within this work. The intensity of the flat decay curve signal was observed to be dependent on both stimulation temperatures and doses. It was demonstrated that for this specific signal, thermally assisting activation energy of almost 1 eV stands as a prevalent feature, indicating that this TA – OSL signal with flat shape originates from very deep traps with activation energy under the conduction band of the order of 3 eV. This suggests that such a trap could provide signal with adequate stability for dating back to a million years, or even more. The dose response linearity for high attributed doses strongly supports the application of Single Aliquot Regenerative TA – OSL for equivalent dose estimations. However, the high recuperation values, of the order of 30%, indicating possible underestimation of the equivalent doses, along with recycling ratio values of around 1.25, stand as drawbacks that limit the use of such TA – OSL signal in single aliquot regenerative protocols for equivalent dose estimations.
•TA – OSL signal with a flat curve shape, without a rapidly decaying component was measured at steady elevated temperatures from quartz.•Thermally assisting activation energy of almost 1 eV stands as a prevalent feature.•Flat TA – OSL originates from VDT with activation energy under the conduction band of the order of 3 eV.•Dose response linearity for high attributed doses strongly supports the application of SAR TA – OSL protocols.•High recycling ratio and recuperation values are drawbacks for widespread SAR TA – OSL applications.
