A CFD-based approach to study the deposition and distribution behaviour of 212Pb in a calibration chamber.

Among the several aspects of decay products behavior, deposition is of special significance because of its prominent role in the activity removal from the environment, which eventually results in the occurrence of decay product disequilibrium with the parent gas. This point is particularly important in case of thoron dosimetry where thoron progeny 212Pb accounts for the most of the radiological dose. The deposition depends on the size distribution of decay products and the structure of air turbulence at the air-surface interface. In the present work, the effect of varying air-flow (fan speed) and aerosol count median diameter (CMD) was studied on the deposition and distribution profile of 212Pb using computational fluid dynamics (CFD). The simulations have been carried out in a cubical calibration chamber of volume 8 m3, facilitated at RP&AD, BARC. Simulated results showed that the increase of total depositional loss rate of attached fraction of 212Pb due to increase of the fan speed was significant for CMD up to 400 nm, beyond which this effect started becoming less prominent with increasing diameter. Besides, a minimum of the total depositional loss rate curve was seen to be shifted to the higher CMD with increase of the fan speed. CFD results were found to be in good agreement with experimental observations obtained in the controlled conditions with thoron source.

A CFD-based approach to optimize operating parameters of a flow-through scintillation cell for measurement of 220Rn in indoor environments.

The measurements and monitoring of 222Rn/220Rn have been of emerging interest in occupational environments particularly in radium/thorium handling facilities and environments with monazite deposits for the inhalation dosimetry. The performance of a flow-through Lucas scintillation cell (LSC) for long run 220Rn measurements, depends upon the exact distribution pattern of 220Rn and its decay products in the LSC which can vary with the design of inlet path and flow rates. In this work, the CFD technique has been used to study the concentration profiles of 220Rn and its decay products in LSC for varying flow rates and inlet needle lengths. The variation of alpha production efficiency (ηα) is computed and analyzed for each case; aiming to select the best operating range of parameters for the optimum performance of LSC for 220Rn measurements. It is seen that LSC can be operated in the flow rate ranging from 0.6 to 1 lpm with inlet needle length varying from 22.5 to 45 mm for improved sensitivity.

Correction: Particle removal from air by face masks made from Sterilization Wraps: Effectiveness and Reusability.

[This corrects the article DOI: 10.1371/journal.pone.0240398.].

Particle removal from air by face masks made from Sterilization Wraps: Effectiveness and Reusability.

Wearing face masks is highly recommended to prevent SARS-CoV-2 transmission in health care workers and for the general public. The demand for high quality face masks has seen an upsurge in the recent times, leading to exploration of alternative economic and easily available options, without compromising on the quality. Particle removal from air in terms of capture efficiency of the filter media or the face mask is a crucial parameter for testing and quality assurance. Short-term reusability of the face masks is also an important aspect as the demand for masks will potentially outstrip the supply in future. Sterilization Wraps, which are used to wrap sterile surgical instruments, have shown a promising performance in terms of removal of particles from air. In this study, we evaluate the particle filtration characteristics of face masks made of 2 different metric weights [45 and 60 gram per square metre (GSM)] respectively, using locally available Sterilization Wraps. The aerosol filtration characteristics were also studied after sterilisation by different techniques such as heat with 50% humidity (thermal treatment), ethylene oxide (ETO), steam and radiation dose of 30kGy. We found that 60 GSM face mask had particle capture efficiency of 94% for total particles greater than 0.3 microns and this capture efficiency was maintained even after sterilisation with ETO and thermal treatment. The cost of producing these masks was 30 US cents/mask at our institute. Our study suggests that sterilization wrap material made of non-woven polypropylene spunbond-meltblown-spunbond (SMS) fibres could be an appropriate readily available inexpensive material for making face masks or N95 respirators.

A data driven epidemic model to analyse the lockdown effect and predict the course of COVID-19 progress in India.

We propose a data driven epidemic model using the real data on the infection, recovery and death cases for the analysis of COVID-19 progression in India. The model assumes continuation of existing control measures such as lockdown and quarantines, the suspected and confirmed cases and does not consider the scenario of 2nd surge of the epidemic due to any reason. The model is arrived after least square fitting of epidemic behaviour model based on theoretical formulation to the real data of cumulative infection cases reported between 24 March 2020 and 30May 2020. The predictive capability of the model has been validated with real data of infection cases reported during June 1-10, 2020. A detailed analysis of model predictions in terms of future trend of COVID-19 progress individually in 18 states of India and India as a whole has been attempted. Infection rate in India, as a whole, is continuously decreasing with time and has reached 3 times lower than the initial infection rate after 6 weeks of lock down suggesting the effectiveness of the lockdown in containing the epidemic. Results suggest that India, as a whole, could see the peak and end of the epidemic in the month of July 2020 and March 2021 respectively as per the current trend in the data. Active infected cases in India may touch 2 lakhs or little above at the peak time and total infected cases may reach over 19 lakhs as per current trend. State-wise results have been discussed in the manuscript. However, the prediction may deviate particularly for longer dates, as assumptions of model cannot be met always in a real scenario. In view of this, a real time application (COV-IND Predictor) has been developed which automatically syncs the latest data from the national COVID19 dash board on daily basis and updates the model input parameters and predictions instantaneously. This real time application can be accessed from the link: https://docs.google.com/spreadsheets/d/1fCwgnQ-dz4J0YWVDHUcbEW1423wOJjdEXm8TqJDWNAk/edit?usp=sharing and can serve as a practical tool for policy makers to track peak time and maximum active infected cases based on latest trend in data for medical readiness and taking epidemic management decisions.

Multifaceted applications of pre-mature chromosome condensation in radiation biodosimetry.

BACKGROUND: Biodosimetry with persistent cytogenetic indicators in peripheral blood lymphocytes (PBLs) plays crucial role in regulatory/medical management of individuals overexposed to radiation. Conventional methods require ∼48 h culture and have limited dose range (0.1-5Gy) applications due to checkpoint arrest/poor stimulation. G0-Phase Premature chromosome condensation (G0-PCC) allows chromosome aberration analysis within hours after blood collection. Due to high skill demand, applications of G0-PCC were not very well explored and being re-visited worldwide. Among all aberrations, analysis of excess chromosomal fragments is quickest. Radiation dose response curve for the fragments has been reported. PURPOSE: In present study, excess fragment analysis has been addressed in detail, in addition to validation of radiation dose response curve, gender variation in the response, dose dependent repair kinetics, minimum detection limit (MDL), duration and accuracy of final dose estimation with 5blindfolded, ex vivo irradiated samples have been studied. In extension, feasibility of multiparametric dosimetry with Fluorescent in situ hybridization (FISH) based endpoints were qualitatively explored. MATERIAL AND METHODS: PBLs were exposed to Gamma-Radiation and G0-PCC was performed at different time points. Decay kinetics and dose response curve were established. Gender Variation of the frequency of the fragments was assessed at 0, 2 and 4 Gy. FISH was performed with G0-PCC applying centromere probe, whole chromosome paints, multi-color FISH and multi-color banding probes. RESULTS: Radiation response curve for fragments was found to be linear (Slope 1.09 ± 0.031 Gy-1). Background frequency as well as dose response did not show significant gender bias. Based on variation in background frequency of fragments MDL was calculated to be ∼0.3 Gy. Kinetics of fragment tested at 0, 4, 8, 16 and 24 h showed exponential decay pattern from 0 to 8 h and without further decay. Final dose estimation of five samples was completed within 13 man-hours. Dicentric chromosomes, translocations, insertions and breaks were identifiable in combination with centromere FISH and WCP. Advanced methods employing multicolor FISH and multi-color banding were also demonstrated with PCC spreads. CONCLUSION: G0-PCC, can be useful tool for high dose biodosimetry with quick assessment of fragment frequency. Further, it holds potential for multi-parametric dosimetry in combination with FISH.

Unexplored aspects of unipolar ionizer characteristics in context of indoor air cleaning.

Indoor air pollution affects human health via acute and chronic exposure. Traditionally, filter systems have been used for indoor air cleaning; however, issues like filter life and routine maintenance remain associated with their operation. Ionizers are emerging as a potential candidate for indoor air cleaning. A major part of previous studies intended to "project ionizers as air cleaners" focus on particle removal in different conditions. But indices representing charge effects have not been given due attention. This study focuses on the measurement of spatial profile of ion concentration and aerosol current around a single ionizer and a circular array of five ionizers. The distribution of ion concentration around the system/array was found to be isotropic in the absence of ventilation. Aerosol current values under ionizer action have been measured for the first time. Results obtained from this work could be instrumental for the design of future ionizer systems with improved efficacy.

Cyto-genotoxicity assessment of potential radioprotector, 3,3'-diselenodipropionic acid (DSePA) in Chinese Hamster Ovary (CHO) cells and human peripheral blood lymphocytes.

Our previous study showed that 3,3'-diselenodipropionic acid (DSePA), a simple, stable, and water-soluble organoselenium exhibiting glutathione peroxidase (GPx)-like activity offered good radioprotection under in vitro and in vivo conditions. Herein, we investigated the anti-genotoxic effect of DSePA in model cellular systems such as Chinese Hamster Ovary (CHO) cell line and human peripheral lymphocytes after exposure to γ-radiation. The measurements on the induction of γ-H2AX foci and micronuclei frequency in the cell nuclei indicated that pretreatment with DSePA significantly prevented the radiation induced DNA damage or genotoxicity and subsequent cytotoxicity without exerting its own toxicity. The maximum protective effect of DSePA was seen at a pre-treatment concentration of 3 µg/ml. The mechanistic investigations in CHO cells revealed that DSePA pretreatment prevented the radiation induced ROS generation, lipid peroxidation and subsequent apoptosis in these cells. Further, it was seen to augment the mRNA expressions of GPx2 significantly and GPx4 marginally without causing much change in the total GPx activity after radiation exposure. These results suggested the roles of GPx2 and GPx4 in DSePA mediated radioprotection. In conclusion our results confirm the nongenotoxic nature of the DSePA and validate its radioprotective efficacy and mechanisms of action in model cellular systems.