Publications

A marine section from Um Sohryngkew riverbasin, in Meghalaya,  have been studied for serach of fullerenes and associated carbon polymorphs .  This section is known for Ir-enrichment with an order of magnitude enhancement of Ir and Os, accompanied by unambiguous extinction of planktonic foraminifera, is found in a cm thicklimonitic clay layer in this section..Peak iridium concentration is found to be 13 ng/g. Os/Ir andNi/Ir are estimated to be 0.37 and 196000 respectively.  We reported here the first observation of C60 fullerenes and nano-diamonds in in the iridium-rich Cretaceous-Palaeogene (K-Pg) boundary layer from the Um-Sohryngkew river section of Meghalaya.

Book review on the book written by Professor Jagdish Sinha as a part of History of Science program of Indian National Science Academy, in which I serve as a council member. The reprint is attached herewith for ready reference.

In this study, the evaluation of carbonaceous fine particulate matter (C-PM) was conducted using the SAFAR-India regional model. Two emission inventories were utilized: the newly developed SAFAR inventory and the global EDGAR-HTAP inventory, both for the year 2018. The simulation aimed to capture the seasonal and spatial patterns of black carbon (BC) and organic carbon (OC) concentrations. To validate model results, surface meteorological parameters, and C-PM concentrations were compared with the MERRA reanalysis data for the Indian region. Model simulated surface C-PM concentration with SAFAR emission inventory is found to be slightly overestimated (1.10), whereas simulated results with EDGAR emission inventory is significantly underestimated as compared to MERRA data. Model-simulated meteorological parameters showed a better correlation with MERRA reanalysis. Simulated geographical patterns of seasonal mean C-PM with SAFAR emission inventory exhibit quite a better comparison with MERRA reanalysis as against EDGAR simulated results. However, some differences in the present results are visible, particularly over the IGP region, as compared to MERRA data, but they are mainly attributed to a significant difference in the special resolution of present results (much finer) as compared to coarser MERRA data. In the Indo-Gangetic Plain (IGP) region, the concentration of BCSF and OCSF (BC and OC with SAFAR emission, respectively) show the peak during the winter, followed by the post-monsoon season. Although the correlation coefficients of hourly time series of surface BCSF and OCSF concentrations with MERRA over India are high (0.92 and 0.88), the poor RMSE, is attributed mainly to different scales of resolution. The model simulated BC, and OC concentrations with SAFAR emission input capture the pattern of spatial distribution reasonably well. The present evolution of BC and OC will help to better quantify their impact on climate and atmospheric conditions over the Indian region.

The transition trajectory of India's two-wheeler (2W) vehicle segment is studied using a sequential modelling framework for projecting sub-segment-wise 2W fleet, energy demand, and associated CO2 emissions. Road density per capita was identified as a more significant explanatory variable than GDP per capita in estimating 2W fleet size in India. The elasticity method was used to evaluate the 2W vehicle saturation level based on five different indirect parameters. It was found that population density had the highest impact (48%), followed by urbanization (31%) and adult population share (16%). The impact of the total cost of ownership was negligible. The mean 2W vehicle saturation level was calculated to be 314 while the ownership was found to be 207, 265, and 297 vehicles per 1000 people by 2030, 2040, and 2050, respectively. Scooters were found to be leading the e-transition of 2Ws but a successful e-transition of India's 2Ws would not be achieved without transitioning the motorcycles. Two motorcycle clusters were identified that offer economies of scale towards e-transitioning. Closer scrutiny of six plausible e-transition scenarios showed that a 50% penetration of E−2Ws is unattainable before 2045. The biggest obstacle in achieving high E−2W penetration in India would be the limited capacity to supply indigenously produced vehicles. A high import dependence on battery technology and critical raw materials would limit the energy transition and diversification of the Indian road transport sector. India should follow the mass adoption-driven diffusion pathway in the short-to-medium term and the affordability-constraint diffusion pathway in the long term to achieve the best results in terms of reduction in energy demand and associated emissions for the 2W segment. The gains from the e-transition of the road transport sector would not be substantial without a simultaneous transition in the country's electricity generation mix away from coal-based thermal power.

This study evaluates the performance of the vertical cylindrical annular reactor configuration, considering innovative radial airflow configurations. From a detailed parametric study, the most suitable reactor geometry and flow arrangement have been identified based on standard performance metrics.

This work suggests a mechanism for development of drug resistance in epilepsy patients, when the post-synaptic neurons express non-standard ALPHA4 proteins in the synaptic GABARA receptor. The structural details can be useful in developing drugs effective against resistant epilepsy.