A novel approach for estimation of aboveground biomass of a carbon-rich mangrove site in India.

Mangroves can play a crucial part in climate change mitigation policies due to their high carbon-storing capacity. However, the carbon sequestration potential of Indian mangroves generally remained unexplored to date. In this study, multi-temporal Sentinel-1 and 2 data-derived variables were used to estimate the AGB of a tropical carbon-rich mangrove forest of India. Ensemble prediction of multiple machine learning algorithms, including Random Forest (RF), Gradient Boosted Model (GBM), and Extreme Gradient Boosting (XGB), were used for AGB prediction. The multi-temporal dataset was used in two different ways to find the most suitable method of using them. The results of the analysis showed that the modeling field measured AGB with individual date data values results in estimates with root mean square errors (RMSE) ranging from 149.242 t/ha for XGB to 151.149 t/ha for the RF. Modeling AGB with the average and percentile metrics of the multi-temporal image stack improves the prediction accuracy of AGB, with RMSE ranging from 81.882 t/ha for the XGB to 74.493 t/ha for the RF. The AGB modeling using ensemble prediction showed further improvement in accuracy with an RMSE of 72.864 t/ha and normalized RMSE of 11.38%. In this study, the intra-seasonal variation of Sentinel-1 and 2 data for mangrove ecosystems was explored for the first time. The variations in remotely sensed variables could be attributed mainly to soil moisture availability and rainfall in the mangrove ecosystem. The efficiency of Sentinel-1 and 2 data-derived variables and ensemble prediction of machine learning models for Indian mangroves were also explored for the first time. The methodologies established in this study can be used in the future for accurate prediction and repeated monitoring of AGB for mangrove ecosystems.

Water quality assessment of the Ganges River during COVID-19 lockdown.

Ganges River water quality was assessed to record the changes due to the nation-wide pandemic lockdown. Satellite-based (Sentinel-2) water quality analysis before and during lockdown was performed for seven selected locations spread across the entire stretch of the Ganges (Rishikesh-Dimond Harbour). Results revealed that due to the lockdown, the water quality of the Ganges improved with reference to specific water quality parameters, but the improvements were region specific. Along the entire stretch of Ganges, only the Haridwar site showed improvement to an extent of being potable as per the threshold set by the Central Pollution Control Board, New Delhi, India. A 55% decline in turbidity at that site during the lockdown was attributed to the abrupt halt in pilgrimage activities. Absorption by chromophoric dissolved organic matter which is an indicator of organic pollution declined all along the Ganges stretch with a maximum decline at the downstream location of Diamond Harbour. Restricted discharge of industrial effluent, urban pollution, sewage from hotels, lodges, and spiritual dwellings along the Ganges are some of the reasons behind such declines. No significant change in the geographic trend of chlorophyll-a was observed. The findings of this study highlight the importance of regular monitoring of the changes in the Ganges water quality using Sentinel-2 data to further isolate the anthropogenic impact, as India continues the phase-wise opening amidst the pandemic.

Study of thermoluminescence (TL) and optically stimulated luminescence (OSL) from α-keratin protein found in human hairs and nails: potential use in radiation dosimetry.

The thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of human nails and hairs containing α-keratin proteins have been investigated. For the present studies, black hairs and finger nails were selectively collected from individuals with ages between 25 and 35 years. The collected hairs/nails were cut to a size of < 1 mm and cleaned with distilled water to remove dirt and other potential physical sources of contamination. All samples were optically beached with 470 nm of LED light at 60 mW/cm(2) intensity and irradiated by a (60)Co γ source. The hair and nail samples showed overlapping multiple TL glow peaks in the temperature range from 70 to 210 ° C. Continuous wave (CW)-OSL measurements of hair samples at a wavelength of 470 nm showed the presence of two distinct OSL components with photoionization cross section (PIC) values of about 1.65 × 10(-18) cm(2) and about 3.48 × 10(-19) cm(2), while measurements of nail samples showed PIC values of about 6.98 × 10(-18) cm(2) and about 8.7 × 10(-19) cm(2), respectively. This difference in PIC values for hair and nail samples from the same individual is attributed to different arrangement of α-keratin protein concentrations in the samples. The OSL sensitivity was found to vary ± 5 times among nail and hair samples from different individuals, with significant fading (60% in 11 h) at room temperature. The remaining signal (after fading) can be useful for dose estimation when a highly sensitive OSL reader is used. In the absorbed dose range of 100 mGy-100 Gy, both the TL and OSL signals of hair and nail samples showed linear dose dependence. The results obtained in the present study suggest that OSL using hair and nail samples may provide a supplementary method of dose estimation in radiological and nuclear emergencies.

OSL and thermally assisted OSL response in dental enamel for its possible application in retrospective dosimetry.

Dental enamel was studied for its thermoluminescence (TL) and optically stimulated luminescence (OSL) defects. The TL studies showed a wide glow curve with multiple peaks. The thermally assisted OSL (TA-OSL) studies showed that the integrated TA-OSL and thus OSL signal increases with readout temperature between 100 and 250 °C, due to the temperature dependence of OSL. The thermally assisted energy E A associated with this increase is found to be 0.21 ± 0.015 eV. On the other hand, the signal intensity decreases with temperature between 260 and 450 °C. This decrease could be due to depletion of OSL active traps or possible thermal quenching. The increase of the OSL signal at increased temperature can be used to enhance the sensitivity of dental enamel for ex vivo measurements in retrospective dosimetry. The emission and excitation spectra of its luminescence centers were studied by photoluminescence and were found to be at 412 and 324 nm, respectively. It was found to possess multiple OSL active traps having closely lying photoionization cross sections characterized by continuous wave OSL and nonlinear OSL methods. The investigated dental enamel samples showed a linear OSL dose response up to 500 Gy. The dose threshold was found to be 100 mGy using a highly sensitive compact OSL reader with blue LED (470 nm) stimulation.

DEVELOPMENT OF OPTICALLY STIMULATED LUMINESCENCE BADGE READER SYSTEM FOR INDIVIDUAL MONITORING OF RADIATION WORKERS.

A new Optically Stimulated Luminescence Badge Reader (OSBARE-1) system has been designed and developed for application in the individual monitoring dosimetry. This badge reader system utilizes the 470-nm light of a blue LED for CW-OSL readout with the help of PMT photon counting module. The developed reader system can process four element 24 OSLD cards within 25 min. These four-element OSLD card consists of the Teflon embedded indigenously developed dosimetric grade α-Al2O3:C phosphor. The minimum measurable dose (MMD) was found to be ~26 µGy for these OSLD cards with reproducibility of ~1.12%. The various operational parameters such as variation in the dark counts, OSL scattering background counts and reproducibility have been studied in detailed for this reader system. The dosimetric studies performed on this developed reader system found to have a great potential for the OSLD-based large-scale personnel monitoring program for the radiation workers.

Complete eversion and prolapse of bladder following pulling out of a Foley catheter concurrent with uterine prolapse.

Complete eversion and transurethral prolapse of the urinary bladder is rare. We report a case of complete eversion and prolapse of bladder that occurred due to self pulling out of an indwelling Foley catheter in a 72-year-old woman. She presented with retention of urine concurrent with complete uterine procidentia. An indwelling Foley catheter was given to relieve the retention. The senile lady pulled out the catheter resulting in complete transurethral prolapse with bladder eversion. Under injection Midazolam sedation and with application of xylocain jelly the prolapsed bladder could be reduced manually back through the urethra. Definite corrective surgery was done later for the uterine prolapse.

Na2SiF6:Cu,P: a new OSL phosphor for the radiation dosimetric applications.

A new Cu,P-doped, sodium fluorosilicate-based optically stimulated luminescence (OSL) phosphor is developed. This phosphor shows good OSL properties, and the sensitivity is comparable with that of the commercial Al(2)O(3):C (Landauer, Inc.) phosphor. For the luminescence averaged over initial 1 s, blue-stimulated luminescence and green-stimulated luminescence sensitivities were found to be 0.76 and 3.8 times, respectively, of Al(2)O(3):C (Landauer, Inc.) with 28 % of post-irradiation fading in 3 days and nil thereafter. The simple preparation procedure, fast decay, very good sensitivity and moderate fading will make this phosphor suitable for radiation dosimetry, using OSL.