TL-SDA: A designed toolkit for the deconvolution analysis of thermoluminescence glow curves.

In the present study, a graphical user interface (GUI) toolkit has been developed to analyze the thermoluminescence (TL) glow-curve and evaluate the trapping parameters using TL expression based on the one-trap one-recombination model. The basic idea of the deconvolution analysis in the developed toolkit is based on performing a sequence of successful fits, where the information provided by each fit is used by the next fit until the deconvolution of the entire glow curve approaches an optimum solution. The starting values and ranges of the fitting parameters can be controlled and adjusted to improve the deconvolution analysis of complex structure glow curves. The designed toolkit is also supported by the background-subtraction option to improve the analysis at low irradiation dose levels. The expanded uncertainty at the 95 % confidence level of the fitted trapping parameters is also provided. All the evaluations performed using the designed toolkit are allowed to be extracted into an Excel spreadsheet. The TL-SDA toolkit can be freely downloaded from: TLSDA_v1 - File Exchange - MATLAB Central (https://www.mathworks.com/matlabcentral/fileexchange/154136-tlsda_v1-1).

Stimulated luminescence; Analysis of complex signals and fitting of dose response curves using analytical expressions based on the Lambert W function implemented in a commercial spreadsheet.

Thermoluminescence (TL) and optically stimulated luminescence (CW-OSL, LM-OSL) are widely used by the scientific community in different applications. In order for the information of a glow or decay curve to be used correctly, the deconvolution of the corresponding curve is essential. Nowadays, there are plethora of deconvolution methods with none of them being dominant and universal. Recently, researchers created some new analytical equations for the TL, CW-OSL and the LM-OSL phenomena, based on the Lambert W function, with the use of a single master equation, as well as some new dose response curves based on a) the simple One Trap One Recombination (OTOR) model and b) the more complex Two Traps One Recombination (TTOR) model. The main aim of the study is to recreate these five expressions in different Excel spreadsheets, for a more practical use. The first step is the creation of a computational code of the Lambert W function in VBA at Excel. After that aim is achieved, five spreadsheets were created, namely the TL deconvolution, the CW-OSL deconvolution, the LM-OSL deconvolution, the OTOR model Dose response and the TTOR Dose response. In order to run some tests using these spreadsheets, four different sets of experimental data originated from different sources were used each time, with the calculated values being compared to the literature. In the end, the present study provides some notes and discussion about the applications of the newly created deconvolution spreadsheets.

Influence of scatter data and temperature lag on the analysis of thermoluminescence glow peak: A Monte Carlo simulation study.

The effects of the scattering data that might appear at the low radiation doses and the temperature lag that might occur between the heater pan and the detector on the thermoluminescence (TL) glow-curve have been addressed. The scattering data were mathematically induced in the TL glow curve using the Monte Carlo (MC) algorithm. While the phenomenon of the temperature lag has been simulated, assuming an exponential function. The deconvolution analysis has been carried out by TL expressions based on a presumed kinetics order value in comparison with the general-order kinetics equation. It has been found that even though the glow peak is known to obey the first- or second-order kinetics model, using the general-order kinetics equation in the deconvolution analysis is better than using the corresponding model equation.

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.

Association of antiviral therapy with reduced disease progression in chronic Hepatitis B patients: Results from a nation-wide cohort study.

BACKGROUND AND AIMS: Although effective treatment in terms of inducing virological and biochemical response for chronic hepatitis B (CHB) is available, its effect on the clinical course of the disease has not yet been accurately estimated. Objective of this study was to evaluate the effect of antiviral therapy and its type [interferon +/- nucleos(t)ide analogs (NAs) vs. NAs] on the occurrence of a clinical event (liver decompensation, liver transplant, hepatocellular carcinoma and death from a liver-related cause) in CHB patients. METHODS: The study population was derived from the HEPNET-Greece, a nationwide cohort study aimed to evaluate the current epidemiological course of viral hepatitis. To account for time-dependent confounding, Cox marginal structural models were used to analyze data. RESULTS: Thirty out of 2,125 eligible patients experienced a clinical event during their follow-up. When comparing treated to untreated individuals, the hazard ratio (HR) for a clinical event was 0.39 (95% CI: 0.16-0.98; p =0.044) in the whole sample, whereas there were indications of a more intense effect in the subgroup of patients with cirrhosis at presentation (HR =0.16, 95% CI: 0.02-1.21; p =0.075). The effect of Interferon initiated treatment was not significantly different of that of NAs. There was some evidence, albeit not statistically significant, of a protective treatment effect on hepatocellular carcinoma development (HCC). CONCLUSIONS: Data from observational studies can provide useful inference, provided they are analyzed appropriately. The current study has shown that the available treatment options for CHB offer a significant clinical benefit to CHB infected individuals. Hippokratia 2016, 20(3): 214-221.

The deconvolution of thermoluminescence glow-curves using general expressions derived from the one trap-one recombination (OTOR) level model.

The new developed thermoluminescence (TL) glow-peak expressions derived from the one trap-one recombination (OTOR) level model were used to analyze the TL glow-curves recorded with linear and exponential heating function profiles under various experimental conditions. The results showed that these expressions can, accurately, analyze the TL glow-curves even with the overlapped glow-peaks. Low values of R=An/Am were reported for glow-peaks in different TL materials. A glow-peak with the possibility of An>Am was also pointed out.

Computerised curve deconvolution of TL/OSL curves using a popular spreadsheet program.

This paper exploits the possibility of using commercial software for thermoluminescence and optically stimulated luminescence curve deconvolution analysis. The widely used software package Microsoft Excel, with the Solver utility has been used to perform deconvolution analysis to both experimental and reference glow curves resulted from the GLOw Curve ANalysis INtercomparison project. The simple interface of this programme combined with the powerful Solver utility, allows the analysis of complex stimulated luminescence curves into their components and the evaluation of the associated luminescence parameters.

Thermoluminescence and optically stimulated luminescence properties of natural barytes.

Heavy, baryte-loaded, concrete is commonly used as radiation shielding material around high energy particle accelerators. Concrete samples received from a shielding block located at CERN cite contain many crystalline inclusions which were identified as barytes by X-ray diffraction analysis and separated by their color, classified as white, orange and green. Basic properties of thermoluminescence (TL) and optically stimulated luminescence (OSL) signals of these barytes samples such as thermal and optical stability, repeatability and mainly the linearity of both their luminescence responses were investigated as a function of beta dose. These results are also discussed regarding detailed investigation on the correlation between TL and OSL signals and their implications for retrospective dosimetry.

Natural course of treated and untreated chronic HCV infection: results of the nationwide Hepnet.Greece cohort study.

BACKGROUND: Interferon (IFN-alpha)-based regimens have been used with varying success in the treatment of chronic hepatitis C (CHC) for over two decades. The effect of such treatments on the natural course of CHC has been evaluated in small clinical trials with conflicting results. AIM: To investigate the natural course of IFNalpha-based-treated and untreated patients with CHC by analysing data from the HEPNET.GREECE study. METHODS: We retrospectively analysed 1738 patients from 25 Greek Centres (median age 40.1; males 57.6%; cirrhosis 9.2%), 734 untreated and 993 treated with IFNalpha-based regimens [44.7% sustained viral response (SVR)], followed-up for median 25.2 and 46.8 months, respectively. RESULTS: During follow-up, 48 patients developed liver decompensation and 24 HCC. Older age was significantly related to disease progression (HR = 2.6 per 10 years of increasing age). Stratified by baseline cirrhosis, Cox analysis showed that patients with SVR, but not without SVR, had significantly lower hazard for events compared with nontreated patients (HR = 0.16; P < 0.001), whereas the detrimental effect of older age remained highly significant. Separate group analysis demonstrated that in cirrhosis, the beneficial effect of treatment was evident even without SVR. Treatment effect interacted significantly with age, indicating that older patients, mainly noncirrhotic, gained the most benefit. CONCLUSIONS: IFNalpha-based treatment does alter the natural course of CHC. A protective effect is mostly present in patients with SVR, but older patients, at higher risk of events, gain the greatest benefit. In established cirrhosis, treatment carries a protective effect even among those without SVR.

A short course of preoperative radiotherapy improves prognosis of operable rectal carcinoma: a case control study.

BACKGROUND/AIMS: Randomized Swedish studies demonstrate the efficacy of a 5-fraction course of preoperative radiotherapy for rectal carcinoma. The present study evaluates the results in a single Greek institution over a 10-year period, with a similar regimen. METHODOLOGY: During the period of 1995-2000, 150 consecutive patients with Dukes' B or C rectal cancer were matched to receive preoperative radiotherapy (Group I) or not (Group II). Seventy-five patients received pelvic radiotherapy of 2500cGY/5 fractions, followed by surgery within one week. Radiotherapy was delivered through 4 portals, with the patient lying in the prone position. A CT scan was used to define treatment volume. The 5-fraction course was used for lesions that seemed readily resectable. Patients in both groups received adjuvant chemotherapy. Local recurrence, disease-free interval and 5-year survival were evaluated and analyzed. RESULTS: The disease-free interval was significantly longer in Group I (p < 0.0005). This benefit was mainly due to a significantly lower incidence of local recurrence in Group I (9/75, 12%) compared with Group II (30/75, 40%) (p < 0.0005). The incidence of distant metastases was not significantly different between the 2 groups. The 5-year survival for all patients, who underwent "curative" surgery was significantly higher in Group I (77.3%) as compared to Group II (39%), (p < 0.0005). CONCLUSIONS: Patients with resectable rectal cancer who received 2500cGy/5 fractions preoperative radiotherapy to the pelvis had excellent local control of disease, longer disease-free interval and higher 5-year survival than patients who did not. These patients were able to undergo sphincter preserving surgery and adjuvant chemotherapy.

Case series of transpancreatic septotomy as precutting technique for difficult bile duct cannulation.

BACKGROUND AND STUDY AIMS: Transpancreatic septotomy can be used instead of other precut techniques to facilitate bile duct cannulation after multiple failed attempts. Within the framework of a prospective randomized study on pentoxifylline, precut cases were retrospectively analyzed. PATIENTS AND METHODS: Of 320 endoscopic retrograde cholangiopancreatographies (ERCPs) in 306 patients with various indications who had a naïve papilla, 34 cases of transpancreatic septotomy were identified and compared with 15 needle-knife sphincterotomies; six patients had received both techniques for bile duct access. Complications were defined according to consensus criteria. RESULTS: In the 55 patients in whom precutting techniques were employed, the use of both techniques alone or in combination resulted in a final common bile duct cannulation rate of 81.8%. Five patients developed complications (9.1%). Of the two cases of pancreatitis (3.6%), one was mild and one severe (combined group). Of the three cases with hemorrhage, one was mild (transpancreatic septotomy) and two severe (needle knife). In patients who underwent conventional pull-type sphincterotomy (n = 242), 6.2% developed complications (nine pancreatitis and six hemorrhage). CONCLUSION: In cases of difficult bile duct cannulation, transpancreatic septotomy seems to be a safe alternative to needle-knife precutting with reasonable success rates. It should be studied in prospective randomized trials.

European evidence based consensus on the diagnosis and management of Crohn's disease: current management.

This second section of the European Crohn's and Colitis Organisation (ECCO) Consensus on the management of Crohn's disease concerns treatment of active disease, maintenance of medically induced remission, and surgery. The first section on definitions and diagnosis includes the aims and methods of the consensus, as well as sections on diagnosis, pathology, and classification of Crohn's disease. The third section on special situations in Crohn's disease includes postoperative recurrence, fistulating disease, paediatrics, pregnancy, psychosomatics, extraintestinal manifestations, and alternative therapy for Crohn's disease.

Molecular epidemiology of hepatitis C virus (HCV) in Greece: temporal trends in HCV genotype-specific incidence and molecular characterization of genotype 4 isolates.

This study aimed to estimate the overall HCV genotype distribution and to reconstruct the HCV genotype-specific incidence in Greece during the recent decades. It also focused at the identification of genotype 4 subtype variability in Greek isolates. A total of 1686 chronically infected HCV patients with detectable serum HCV RNA by RT-PCR, belonging to different risk groups were studied. Amplified products from the 5'-noncoding region were typed using a commercially available assay based on the reverse hybridization principle. The HCV genotype-specific incidence was estimated using a previously described back calculation method. HCV genotype 1 was the most prevalent (46.9%) followed by genotype 3 (28.1%), 4 (13.2%), 2 (6.9%) and 5 (0.4%). A high prevalence of genotype 1 (66.3%) in haemophilia patients was recorded whereas HCV genotype 3 was found mainly among patients infected by I.V. drug use (58.2%). Data on the temporal patterns of HCV genotype-specific incidence in Greece revealed a moderate increase (1.3-1.6 times) for genotypes 1 and 4, and a decrease (1.5 times) for genotype 2 from 1970 to 1990, whereas there was a sharp (13-fold) increase for genotype 3. The molecular characterization of 41 genotype 4 HCV isolates belonging to various risk groups revealed that, subtype 4a was the most frequently detected (78%). Phylogenetic comparison of the Greek 4a isolates with all HCV-4a isolates reported worldwide so far revealed a topology which does not discriminate Greek isolates from the others. HCV-4 does not represent a recent introduction in Greece.

Thermoluminescence properties of Chile Guajillo paprika Mexicano.

The thermoluminescence properties of the inorganic dust extracted from the Chile Guajillo (paprika) Mexicano, were studied in order to verify the possibility of using the TL technique to discriminate between irradiated and non irradiated peppers. The inorganic dust was found to consist of quartz 60%, albite (NaAlSi(3)O(8)) 30%, and ortose (KAlSi(3)O(8)) 10%. Its thermoluminescence dose response covers the wide dose range of 1 Gy--10 kGy, which was attributed mainly to feldspars. Its high sensitivity and its stability over 10 irradiation-readout cycles allow the application of a single grain--single aliquot regeneration dosimetry in Chile Guajillo (paprika). Evaluations based on trapping parameters show that thermal fading at room temperature for glow-peaks above 180 degrees C, is not a problem in the dosimetry of paprika.

Computerised glow curve deconvolution using general and mixed order kinetics.

Some accurate glow curve fitting functions for general and mixed order kinetics glow peaks are proposed and discussed. These mathematical expressions are used together with peak search and non-linear minimisation algorithms in order to provide a fast glow curve deconvolution for those materials which cannot be well fitted using first order kinetics. To test the accuracy of the proposed method. the result of the fitting of synthetic glow curves is compared with the original data giving negligible errors for values of parameters currently found in TL materials.

On the possibility of using commercial software packages for thermoluminescence glow curve deconvolution analysis.

This paper explores the possibility of using commercial software for thermoluminescence glow curve deconvolution (GCD) analysis. The program PEAKFIT has been used to perform GCD analysis of complex glow curves of quartz and dosimetric materials. First-order TL peaks were represented successfully using the Weibull distribution function. Second-order and general-order TL peaks were represented accurately by using the Logistic asymmetric functions with varying symmetry parameters. Analytical expressions were derived for determining the energy E from the parameters of the Logistic asymmetric functions. The accuracy of these analytical expressions for E was tested for a wide variety of kinetic parameters and was found to be comparable to the commonly used expressions in the TL literature. The effectiveness of fit of the analytical functions used here was tested using the figure of merit (FOM) and was found to be comparable to the accuracy of recently published GCD expressions for first- and general-order kinetics.

Mapping of the thermal neutron distribution in the lead block assembly of the PS-211 experiment at CERN, using thermoluminescence and nuclear track detectors.

The main purpose of the TARC (Transmutation by Adiabatic Resonance Crossing) experiment (PS-211), was to demonstrate the possibility to destroy efficiently Long-Lived Fission Fragments (LLFF) in Accelerator Driven Systems (ADS). The experimental set-up which consisted of a lead block with dimensions 3.3 x 3.3 x 3 m3, was installed in a CERN Proton Synchrotron (PS) beam line. The proton beam at 2.5 GeV/c and 3.5 GeV/c, was incident in the centre of the lead block assembly producing neutrons via spallation reactions. In this study, neutron flux measurements are presented in the lead block assembly using thermoluminescence and nuclear track detectors. The results are in good agreement with Monte Carlo calculations as well as with the results of the other methods used in the framework of the TARC experiment.

Detailed kinetic study of the thermoluminescence glow curve of synthetic quartz.

A detailed kinetic analysis has been performed of the thermoluminescence (TL) glow curve of high purity synthetic quartz. The kinetic parameters of the glow peak at 110 degrees C were evaluated for doses ranging from 0.1 Gy to 100 Gy using glow curve deconvolution (GCD), initial rise, variable heating ratc and phosphorescence decay methods. All the methods gave results that agree within the experimental errors.