Synthesis, characterization and thermoluminescence properties of LiCaPO4 phosphor for ionizing radiation dosimetry.

Many minerals and compounds show thermoluminescence (TL) properties but only a few of them can meet the requirements of an ideal dosimeter. Several phosphate materials have been studied for low-dose dosimetryin recent times. Among the various phosphates, ABPO4-type material shows interesting TL properties. In this study, an ABPO4-type (A = Lithium, B=Calcium) phosphor is synthesized using a modified solid-state diffusion method. Temperature is maintained below 800 °C in every step of phosphor preparation to obtain the pure phase of Lithium calcium phosphate (LiCaPO4). The purpose of this work is to synthesize LiCaPO4 using a simple method, examine its structural and luminescence properties in order to gain a deeper understanding of its TL characteristics. The general TL properties, such as TL glow curve, dose linearity, sensitivity, and fading, are investigated. Additionally, this study aims to determine various kinetic parameters through Glow Curve Deconvolution (GCD) method using the Origin Lab software together with the Chen model. XRD analysis confirmed the phase purity of the phosphor with a rhombohedral structure. Lattice parameters, unit cell volume, grain size, dislocated density, and microstrain were also calculated from XRD data. Raman analysis and Fourier Transform Infrared analysis were used to collect information about molecular bonds, vibrations, identity, and structure of the phosphor. To investigate TL properties and associated kinetic parameters, the phosphor was irradiated with 6.0 MV (photon energy) and 6.0 MeV (electron energy) from a linear accelerator for doses ranging from 0.5 Gy to 6.0 Gy. For both photon and electron energy, TL glow curves have two identical peaks near 200 °C and 240 °C.The TL glow curves for 0.5 Gy-6 Gy are deconvoluted, then fitted with the appropriate model and then calculated the kinetic parameters. Kinetic parameters such as geometric factor (µg), order of kinetics, activation energy (E), and frequency factor (s) are obtained from Chen's peak shape method. The dose against the TL intensity curve shows that the response is almost linear in the investigated dose range. For photon and electron energy, the phosphor is found to be the most sensitive at 2.0 Gy and 4.0 Gy, respectively. The phosphor shows a low fading and after 28 days of exposure, it shows a signal loss of better than 3%. The studied TL properties suggest the suitability of LiCaPO4 in radiation dosimetry and associated fields.

The impact of climate variables on marine fish production: an empirical evidence from Bangladesh based on autoregressive distributed lag (ARDL) approach.

Several studies have highlighted the significant impact of climate change on agriculture. However, there have been little empirical enquiries into the impact of climate change on marine fish production, particularly in Bangladesh. Hence, this study aims to investigate the impact of climate change on marine fish production in Bangladesh using data from 1961 to 2019. Data were obtained from the Food and Agriculture Organization, Bangladesh Meteorological Department, the World Development Indicators, and the National Oceanic and Atmospheric Administration. The autoregressive distributed lag (ARDL) model was used to describe the dynamic link between CO2 emissions, average temperature, Sea Surface Temperature (SST), rainfall, sunshine, wind and marine fish production. The ARDL approach to cointegration revealed that SST (ß = 0.258), rainfall (ß =0.297), and sunshine (ß =0.663) significantly influence marine fish production at 1% and 10% levels in the short run and at 1% level in the long run. The results also found that average temperature has a significant negative impact on fish production in both short and long runs. On the other hand, CO2 emissions have a negative impact on marine fish production in the short run. Specifically, for every 1% rise in CO2 emissions, marine fish production will decline by 0.11%. The findings of this study suggest that policymakers formulate better policy frameworks for climate change adaptation and sustainable management of marine fisheries at the national level. Research and development in Bangladesh's fisheries sector should also focus on marine fish species that can resist high sea surface temperatures, CO2 emissions, and average temperatures.

Photonic crystal fibre as a potential medium for radiotherapy dosimetry.

Present study concerns the key thermoluminescence (TL) properties of photonic crystal fibres (PCFs), seeking development of alternatively structured TL materials that are able to offer a advantages over existing passive dosimeters. In terms of their internal structure and light guiding properties the PCFs, collapsed and structured, differ significantly from that of conventional optical fibres. To investigate the dosimetric parameters of the PCFs use was made of a linear accelerator producing a 6 MV photon beam, delivering doses ranging from 0.5 Gy to 8 Gy. The parameters studied included TL response, linearity index, glow curves, relative sensitivity and TL signal fading, the results being compared against those obtained using TLD-100 chips. At 4 Gy photon dose the Ge-doped collapsed PCFs were found to provide a response 27 × that of structured PCF, also giving a TL yield similar to that of standard TLD-100 chips. Over post-irradiation periods of 15 and 30 days collapsed PCF TL signal fading were 8% and 17% respectively, with corresponding values of 37% and 64% for the structured PCF. Trapping parameters including the order of kinetics (b), activation energy (E) and frequency factor (s-1) were assessed with Chen's peak shape method. Lifetime of trapping centre was found to be (2.36 E+03) s and (9.03 E +01) s regarding the collapsed and structured PCF respectively with 6 Gy of photon beam. For the Ge-doped collapsed PCF, the high TL yield, sensitivity and low fading provide the basis of a highly promising system of TLD for radiotherapy applications.

Thermoluminescence characteristics of Ge-doped optical fibers with different dimensions for radiation dosimetry.

Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples ∼0.5cm length are annealed at temperature of 400°C for 1h period to standardize their sensitivities and background. Standard TLD-100 chips are also annealed for 1h at 400°C and subsequently 2h at 100°C to yield the highest sensitivity. TL responses of these fibers show linearity over a wide gamma radiation dose that is an important property for radiation dosimetry. Among all fibers used in this study, 100µm core diameter fiber provides highest response that is 2.6 times than that of smallest core (20µm core) optical fiber. These fiber-samples demonstrate better response than commercial multi-mode optical fiber and also provide low degree of fading about 20% over a period of fifteen days for gamma radiation. Effective atomic number (Zeff) is found in the range (13.25-13.69) which is higher than soft tissue (7.5) however within the range of human-bone (11.6-13.8). All the fibers can also be re-used several times as a detector after annealing. TL properties of the Ge-doped optical fibers indicate promising applications in ionizing radiation dosimetry.

Emergency peripartum hysterectomy in a tertiary care hospital in saudi arabia.

PURPOSE: Post-partum hemorrhage remains an important cause of significant maternal morbidity and mortality throughout the world. The objective of this study was to review the incidence, indications, predisposing factors, and associated complications of emergency peripartum hysterectomy. METHODS: This is a retrospective observational study done in a Tertiary Care Center, Riyadh, Saudi Arabia, between 1983 and 2006. Women who underwent emergency peripartum hysterectomy after cesarean delivery or following vaginal birth due to severe post-partum hemorrhage who did not respond to conservative treatment were included in the study. Data were abstracted from chart reviews. Descriptive analysis was carried out to summarize relevant variables. Primary outcomes included indications, risk factors, maternal morbidity, and mortality. RESULTS: There were 66 emergency peripartum hysterectomies among 155,857 deliveries, which yielded an incidence of 0.04 %. Prior cesarean delivery was present in 88 % of the patients; a majority of the patients were grandmultiparous, Para > 6 (65 %). The incidence of hysterectomy after cesarean delivery was much higher than after vaginal delivery (0.3 vs. 0.01 %). Common indications included placenta accreta (65 %), uterine atony (27 %), and uterine rupture (8 %). The majority of the study cohort (64 %) had undergone total hysterectomy. Post-operatively, 25 patients (38 %) developed DIC, 32 (48.5 %) had febrile illnesses, and 22 (33 %) experienced injury to the urinary tract. The maternal mortality in this study was 4.5 %. CONCLUSIONS: Hysterectomy for the control of obstetric hemorrhage is usually associated with significant mortality and morbidity. Prompt intervention to include peripartum hysterectomy may likely decrease the rate of maternal deaths and significant maternal morbidity.

Obstetric performance of a patient with multiple uterine and cervical fibroids and expectant management of retained placenta.

The aim of this case report is to describe the obstetric performance of a patient with multiple uterine and supravaginal cervical fibroids. A 36-year-old, gravida 3 para 0+2 with multiple uterine and cervical fibroids presented with inevitable abortion at 17 weeks gestation. She had a spontaneous rupture of membranes followed by expulsion of fetus as breech with entrapment of aftercoming head by a cervical fibroid. Oxytocin infusion and digital traction were able to deliver the fetus. The placenta, however, was trapped in the fundal area and could not be delivered under general anesthesia because of mechanical obstruction by the fibroid. Expectant management was successful in expulsion of the placenta within 7 days without complication.