Dr. Pawan Gupta

Dr. Pawan Gupta

  • RSCH AST, EARTH SCIENCES REMOTE SENS
  • NASA/GSFC
  • Huntsville , AL 35812
  • Employer: NASA
  • Brief Bio

    Dr. Gupta is currently a research scientist – earth sciences in Biospheric Sciences Laboratory at NASA's Goddard Space Flight Center. He co-leads NASA's AERONET Program. He has been leading and managing NASA's ARSET Air Quality team for more than ten years now. Dr. Gupta has led the development of more than 50 in-person and online training for ARSET and other NASA programs. He collaborates with the larger global earth science community on training and research. Previously, Dr. Gupta served as the portfolio manager for SERVIR's Applied Science Team. He managed more than 20 research projects spread out across multiple applied science research areas and operational in more than 30 countries. He has experience working with stakeholders, including US government agencies, state and local agencies, non-profit and private sectors, and international agencies (World Bank, WHO). Dr. Gupta's research expertise includes remote sensing methods, data product development, validation, and application development. He has also published more than 50 peer-reviewed research studies focusing on satellite algorithms, air quality, climate, statistical modeling, and machine learning and data fusion techniques. Dr. Gupta is the principal investigator on NASA-funded research projects. He is currently a member of NASA's multiple missions and science teams, including MODIS and VIIRS, NASA's citizen science, Making Earth System Data Records for Use in Research Environments (MEaSUREs), and the Health and Air Quality Applied Science Team (HAQAST). Dr. Gupta is also the lead for a HAQAST tiger team funded by NASA to integrate satellite data into EPA's AirNow air quality monitoring system. Dr. Gupta manages and leads this team, including researchers from multiple agencies, academia, and private sectors, including NOAA and US EPA.

    Research Interests

    Atmospheric Aerosols


    Satellite Remote Sesning of Aerosols & Clouds


    Satellite Remote Sensing of Air Pollution & Air Quality


    Climate Change


    Earth Radiation Budget


    Multi Sensor Data Fusion


    Current Projects

    Applied Remote Sensing Training (ARSET) Program

     http://arset.gsfc.nasa.gov/airquality

    AERONET - AErosol RObotic NETwork

    https://aeronet.gsfc.nasa.gov/

    Positions/Employment

    5/2010 - Present

    Research Scientist

    Universities Space Research Association, NASA Goddard Space Flight Center

    Selected Publications

    Refereed

    Sathe, Y., P. Gupta, M. Bawase, et al. L. Lamsal, F. Patadia, and S. Thipse. 2020. "Surface and Satellite Observations of Air Pollution in India during COVID-19 Lockdown: Implication to Air Quality." Sustainable Cities and Society, 102688 [10.1016/j.scs.2020.102688]

    Remer, L. A., R. C. Levy, S. Mattoo, et al. D. Tanré, P. Gupta, Y. Shi, V. Sawyer, L. A. Munchak, Y. Zhou, M. Kim, C. Ichoku, F. Patadia, R.-R. Li, S. Gassó, R. G. Kleidman, and B. N. Holben. 2020. "The Dark Target Algorithm for Observing the Global Aerosol System: Past, Present, and Future." Remote Sensing, 12 (18): 2900 (In Press) [10.3390/rs12182900]

    Gupta, P., L. A. Remer, F. Patadia, R. C. Levy, and S. A. Christopher. 2020. "High-Resolution Gridded Level 3 Aerosol Optical Depth Data from MODIS." Remote Sensing, 12 (17): 2847 (In Press) [10.3390/rs12172847]

    Gupta, P., P. Doraiswamy, R. Levy, et al. O. Pikelnaya, J. Maibach, B. Feenstra, A. Polidori, F. Kiros, and K. C. Mills. 2018. "Impact of California Fires on Local and Regional Air Quality: The Role of a Low-Cost Sensor Network and Satellite Observations." GeoHealth, [10.1029/2018gh000136]

    Gupta, P., L. A. Remer, R. C. Levy, and S. Mattoo. 2018. "Validation of MODIS 3 km land aerosol optical depth from NASA's EOS Terra and Aqua missions." Atmospheric Measurement Techniques, 11 (5): 3145-3159 [10.5194/amt-11-3145-2018]

    Jethva, H., D. Chand, O. Torres, et al. P. Gupta, A. Lyapustin, and F. Patadia. 2018. "Agricultural Burning and Air Quality over Northern India: A Synergistic Analysis using NASA’s A-train Satellite Data and Ground Measurements." Aerosol and Air Quality Research, 18 (7): 1756-1773 [10.4209/aaqr.2017.12.0583]

    Sherman, J. P., P. Gupta, R. C. Levy, and P. J. Sherman. 2016. "An Evaluation of MODIS-Retrieved Aerosol Optical Depth over a Mountainous AERONET Site in the Southeastern US." Aerosol Air Qual. Res., 16 (12): 3243-3255 [10.4209/aaqr.2015.09.0568]

    Gupta, P., R. C. Levy, S. Mattoo, L. A. Remer, and L. A. Munchak. 2016. "A surface reflectance scheme for retrieving aerosol optical depth over urban surfaces in MODIS Dark Target retrieval algorithm." Atmospheric Measurement Techniques, 9 (7): 3293-3308 [10.5194/amt-9-3293-2016]

    Gupta, P., J. Joiner, A. Vasilkov, and P. K. Bhartia. 2016. "Top-of-the-atmosphere shortwave flux estimation from satellite observations: an empirical neural network approach applied with data from the A-train constellation." Atmospheric Measurement Techniques, 9 (7): 2813-2826 [10.5194/amt-9-2813-2016]

    Naeger, A. R., P. Gupta, B. T. Zavodsky, and K. M. McGrath. 2016. "Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth composites." Atmospheric Measurement Techniques, 9 (6): 2463-2482 [10.5194/amt-9-2463-2016]

    Sinha, P., P. Gupta, D. Kaskaoutis, et al. L. Sahu, N. Nagendra, R. K. Manchanda, Y. B. Kumar, and S. Sreenivasan. 2015. "Estimation of particulate matter from satellite- and ground-based observations over Hyderabad, India." International Journal of Remote Sensing, 36 (24): 6192-6213 [10.1080/01431161.2015.1112929]

    Xiong, X., L. Chen, Y. Liu, U. Cortesi, and P. Gupta. 2015. "Satellite Observation of Atmospheric Compositions for Air Quality and Climate Study." Advances in Meteorology, 2015: 1-2 [10.1155/2015/932012]

    Naeger, A. R., P. Gupta, B. Zavodsky, and K. M. McGrath. 2015. "Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth retrievals." Atmospheric Measurement Techniques Discussions, 8 (10): 10319-10360 [10.5194/amtd-8-10319-2015]

    Aher, G. R., G. V. Pawar, P. Gupta, and P. C. Devara. 2014. "Effect of major dust storm on optical, physical, and radiative properties of aerosols over coastal and urban environments in Western India." International Journal of Remote Sensing, 35 (3): 871-903 [10.1080/01431161.2013.873153]

    Duncan, B. N., A. I. Prados, L. Lamsal, et al. Y. Liu, D. Streets, P. Gupta, E. Hilsenrath, R. A. Kahn, J. E. Nielsen, A. Beyersdorf, S. Burton, A. Fiore, J. Fishman, D. Henze, C. Hostetler, N. A. Krotkov, P. Lee, M. Lin, S. Pawson, G. Pfister, K. E. Pickering, R. B. Pierce, Y. Yoshida, and L. Ziemba. 2014. "Satellite data of atmospheric pollution for U.S. air quality applications: Examples of applications, summary of data end-user resources, answers to FAQs, and common mistakes to avoid." Atmospheric Environment, 94: 647-662 [10.1016/j.atmosenv.2014.05.061]

    Gupta, P., M. Khan, A. M. Da Silva, and F. Patadia. 2013. "MODIS aerosol optical depth observations over urban areas in Pakistan: Quantity and quality of the data for air quality monitoring." Atmospheric Pollution Research, 4 (1): 43-52 [10.5094/APR.2013.005]

    Joiner, J., A. P. Vasilkov, P. Gupta, et al. P. K. Bhartia, P. Veefkind, M. Sneep, J. D. Haan, I. Polonsky, and R. Spurr. 2012. "Fast simulators for satellite cloud optical centroid pressure retrievals; evaluation of OMI cloud retrievals." Atmospheric Measurement Techniques, 5 (3): 529-545 [Full Text (Link)] [10.5194/amt-5-529-2012]

    Kaskaoutis, D. G., R. A. Kahn, P. Gupta, A. Jayaraman, and A. Bartzokas. 2012. "Desert Dust Properties, Modelling, and Monitoring." Advances in Meteorology, 2012 (483632): 1-2 [10.1155/2012/483632]

    Kaskaoutis, D. G., A. K. Prasad, P. G. Kosmopoulos, et al. P. R. Sinha, S. K. Kharol, P. Gupta, H. M. El-Askary, and M. Kafatos. 2012. "Synergistic Use of Remote Sensing and Modeling for Tracing Dust Storms in the Mediterranean." Advances in Meteorology, 2012 (Article ID 861026): 1-14 [10.1155/2012/861026]

    Rashki, A., C. J. Kaskaoutis, C. J. Kaskaoutis, et al. C. J. Kaskaoutis, P. Eriksson, M. Qiang, and P. Gupta. 2012. "Dust storms and their horizontal dust loading in the Sistan region, Iran." Aeolian Research, 5: 51-62 [10.1016/j.aeolia.2011.12.001]

    Christopher, S., P. Gupta, B. Johnson, and J. Haywood. 2011. "Multi-sensor satellite remote sensing of dust aerosols over North Africa during GERBILS." Q.J.R. Meteorol. Soc., 137 (658): 1168-1178 [10.1002/qj.863]

    Haywood, B., T. Johnson, S. R. Osborne, et al. A. Baran, M. Brooks, S. F. Milton, J. Mulcahy, D. Walters, R. Allan, M. Woodage, A. Klaver, P. Formenti, H. E. Brindley, S. Christopher, and P. Gupta. 2011. "Motivation, rationale and key results from the GERBILS Saharan dust measurement campaign." Q.J.R. Meteorol. Soc., 137 (658): 1106-1116 [10.1002/qj.797]

    Gupta, P., and S. A. Christopher. 2009. "Particulate matter air quality assessment using integrated surface, satellite, and meteorological products: 2. A neural network approach." Journal of Geophysical Research: Atmospheres, 114 (D20): [10.1029/2008JD011496]

    Gupta, P., and S. A. Christopher. 2009. "Particulate matter air quality assessment using integrated surface, satellite, and meteorological products: Multiple regression approach." JGR, [DOI 10.1029/2008JD011496]

    Gupta, P., and S. A. Christopher. 2008. "An evaluation of Terra-MODIS sampling for monthly and annual particulate matter air quality assessment over the Southeastern United States." Atmospheric Environment, 42 (26): [doi:10.1016/j.atmosenv.2008.04.044]

    Patadia, F., P. Gupta, S. A. Christopher, and J. S. Reid. 2008. "A Multisensor satellite-based assessment of biomass burning aerosol radiative impact over Amazonia." Journal of Geophysical Research, 113 (D12): [10.1029/2007JD009486]

    Gupta, P., and S. A. Christopher. 2008. "Seven year particulate matter air quality assessment from surface and satellite measurements." Atmos. Chem. Phys., 8: [doi:10.5194/acp-8-3311-2008]

    Patadia, F., P. Gupta, and S. A. Christopher. 2008. "First observational estimates of global clear sky shortwave aerosol direct radiative effect over land." Geophys. Res. Lett, 35 (4): L04810 [10.1029/2007GL032314]

    Gupta, P., F. Patadia, and S. A. Christopher. 2008. "Multisensor Data Product Fusion for Aerosol Research." IEEE Trans. Geosci. Remote Sensing, 46 (5): 1407-1415 [10.1109/TGRS.2008.916087]

    Douglass, A. R., R. S. Stolarski, M. R. Schoeberl, et al. C. H. Jackman, P. Gupta, P. Newman, E. L. Fleming, J. E. Nielsen, and E. L. Fleming. 2008. "Relationship of loss, mean age of air and the distribution of CFCs to stratospheric circulation and implications for atmospheric lifetimes." J. Geophys. Res., 113 (D14): D14309 [10.1029/2007JD009575]

    Gupta, P., S. A. Christopher, M. A. Box, and G. A. Box. 2007. "Multi year satellite remote sensing of particulate matter air quality over Sydney, Australia." IJRS, 28 (20): [10.1080/01431160701241738]

    Gupta, P., S. A. Christopher, J. Wang, et al. R. Gehrig, Y. C. Lee, and N. Kumar. 2006. "Satellite remote sensing of particulate matter and air quality assessment over global cities." Atmospheric Environment, 40 (30): [doi:10.1016/j.atmosenv.2006.03.016]

    Brief Bio

    Dr. Gupta is currently a research scientist – earth sciences in Biospheric Sciences Laboratory at NASA's Goddard Space Flight Center. He co-leads NASA's AERONET Program. He has been leading and managing NASA's ARSET Air Quality team for more than ten years now. Dr. Gupta has led the development of more than 50 in-person and online training for ARSET and other NASA programs. He collaborates with the larger global earth science community on training and research. Previously, Dr. Gupta served as the portfolio manager for SERVIR's Applied Science Team. He managed more than 20 research projects spread out across multiple applied science research areas and operational in more than 30 countries. He has experience working with stakeholders, including US government agencies, state and local agencies, non-profit and private sectors, and international agencies (World Bank, WHO). Dr. Gupta's research expertise includes remote sensing methods, data product development, validation, and application development. He has also published more than 50 peer-reviewed research studies focusing on satellite algorithms, air quality, climate, statistical modeling, and machine learning and data fusion techniques. Dr. Gupta is the principal investigator on NASA-funded research projects. He is currently a member of NASA's multiple missions and science teams, including MODIS and VIIRS, NASA's citizen science, Making Earth System Data Records for Use in Research Environments (MEaSUREs), and the Health and Air Quality Applied Science Team (HAQAST). Dr. Gupta is also the lead for a HAQAST tiger team funded by NASA to integrate satellite data into EPA's AirNow air quality monitoring system. Dr. Gupta manages and leads this team, including researchers from multiple agencies, academia, and private sectors, including NOAA and US EPA.

    Selected Publications

    Refereed

    Sathe, Y., P. Gupta, M. Bawase, et al. L. Lamsal, F. Patadia, and S. Thipse. 2020. "Surface and Satellite Observations of Air Pollution in India during COVID-19 Lockdown: Implication to Air Quality." Sustainable Cities and Society 102688 [10.1016/j.scs.2020.102688]

    Remer, L. A., R. C. Levy, S. Mattoo, et al. D. Tanré, P. Gupta, Y. Shi, V. Sawyer, L. A. Munchak, Y. Zhou, M. Kim, C. Ichoku, F. Patadia, R.-R. Li, S. Gassó, R. G. Kleidman, and B. N. Holben. 2020. "The Dark Target Algorithm for Observing the Global Aerosol System: Past, Present, and Future." Remote Sensing (In Press) 12 (18): 2900 [10.3390/rs12182900]

    Gupta, P., L. A. Remer, F. Patadia, R. C. Levy, and S. A. Christopher. 2020. "High-Resolution Gridded Level 3 Aerosol Optical Depth Data from MODIS." Remote Sensing (In Press) 12 (17): 2847 [10.3390/rs12172847]

    Gupta, P., P. Doraiswamy, R. Levy, et al. O. Pikelnaya, J. Maibach, B. Feenstra, A. Polidori, F. Kiros, and K. C. Mills. 2018. "Impact of California Fires on Local and Regional Air Quality: The Role of a Low-Cost Sensor Network and Satellite Observations." GeoHealth [10.1029/2018gh000136]

    Gupta, P., L. A. Remer, R. C. Levy, and S. Mattoo. 2018. "Validation of MODIS 3 km land aerosol optical depth from NASA's EOS Terra and Aqua missions." Atmospheric Measurement Techniques 11 (5): 3145-3159 [10.5194/amt-11-3145-2018]

    Jethva, H., D. Chand, O. Torres, et al. P. Gupta, A. Lyapustin, and F. Patadia. 2018. "Agricultural Burning and Air Quality over Northern India: A Synergistic Analysis using NASA’s A-train Satellite Data and Ground Measurements." Aerosol and Air Quality Research 18 (7): 1756-1773 [10.4209/aaqr.2017.12.0583]

    Sherman, J. P., P. Gupta, R. C. Levy, and P. J. Sherman. 2016. "An Evaluation of MODIS-Retrieved Aerosol Optical Depth over a Mountainous AERONET Site in the Southeastern US." Aerosol Air Qual. Res. 16 (12): 3243-3255 [10.4209/aaqr.2015.09.0568]

    Gupta, P., R. C. Levy, S. Mattoo, L. A. Remer, and L. A. Munchak. 2016. "A surface reflectance scheme for retrieving aerosol optical depth over urban surfaces in MODIS Dark Target retrieval algorithm." Atmospheric Measurement Techniques 9 (7): 3293-3308 [10.5194/amt-9-3293-2016]

    Gupta, P., J. Joiner, A. Vasilkov, and P. K. Bhartia. 2016. "Top-of-the-atmosphere shortwave flux estimation from satellite observations: an empirical neural network approach applied with data from the A-train constellation." Atmospheric Measurement Techniques 9 (7): 2813-2826 [10.5194/amt-9-2813-2016]

    Naeger, A. R., P. Gupta, B. T. Zavodsky, and K. M. McGrath. 2016. "Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth composites." Atmospheric Measurement Techniques 9 (6): 2463-2482 [10.5194/amt-9-2463-2016]

    Sinha, P., P. Gupta, D. Kaskaoutis, et al. L. Sahu, N. Nagendra, R. K. Manchanda, Y. B. Kumar, and S. Sreenivasan. 2015. "Estimation of particulate matter from satellite- and ground-based observations over Hyderabad, India." International Journal of Remote Sensing 36 (24): 6192-6213 [10.1080/01431161.2015.1112929]

    Xiong, X., L. Chen, Y. Liu, U. Cortesi, and P. Gupta. 2015. "Satellite Observation of Atmospheric Compositions for Air Quality and Climate Study." Advances in Meteorology 2015 1-2 [10.1155/2015/932012]

    Naeger, A. R., P. Gupta, B. Zavodsky, and K. M. McGrath. 2015. "Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth retrievals." Atmospheric Measurement Techniques Discussions 8 (10): 10319-10360 [10.5194/amtd-8-10319-2015]

    Aher, G. R., G. V. Pawar, P. Gupta, and P. C. Devara. 2014. "Effect of major dust storm on optical, physical, and radiative properties of aerosols over coastal and urban environments in Western India." International Journal of Remote Sensing 35 (3): 871-903 [10.1080/01431161.2013.873153]

    Duncan, B. N., A. I. Prados, L. Lamsal, et al. Y. Liu, D. Streets, P. Gupta, E. Hilsenrath, R. A. Kahn, J. E. Nielsen, A. Beyersdorf, S. Burton, A. Fiore, J. Fishman, D. Henze, C. Hostetler, N. A. Krotkov, P. Lee, M. Lin, S. Pawson, G. Pfister, K. E. Pickering, R. B. Pierce, Y. Yoshida, and L. Ziemba. 2014. "Satellite data of atmospheric pollution for U.S. air quality applications: Examples of applications, summary of data end-user resources, answers to FAQs, and common mistakes to avoid." Atmospheric Environment 94 647-662 [10.1016/j.atmosenv.2014.05.061]

    Gupta, P., M. Khan, A. M. Da Silva, and F. Patadia. 2013. "MODIS aerosol optical depth observations over urban areas in Pakistan: Quantity and quality of the data for air quality monitoring." Atmospheric Pollution Research 4 (1): 43-52 [10.5094/APR.2013.005]

    Joiner, J., A. P. Vasilkov, P. Gupta, et al. P. K. Bhartia, P. Veefkind, M. Sneep, J. D. Haan, I. Polonsky, and R. Spurr. 2012. "Fast simulators for satellite cloud optical centroid pressure retrievals; evaluation of OMI cloud retrievals." Atmospheric Measurement Techniques 5 (3): 529-545 [Full Text (Link)] [10.5194/amt-5-529-2012]

    Kaskaoutis, D. G., R. A. Kahn, P. Gupta, A. Jayaraman, and A. Bartzokas. 2012. "Desert Dust Properties, Modelling, and Monitoring." Advances in Meteorology 2012 (483632): 1-2 [10.1155/2012/483632]

    Kaskaoutis, D. G., A. K. Prasad, P. G. Kosmopoulos, et al. P. R. Sinha, S. K. Kharol, P. Gupta, H. M. El-Askary, and M. Kafatos. 2012. "Synergistic Use of Remote Sensing and Modeling for Tracing Dust Storms in the Mediterranean." Advances in Meteorology 2012 (Article ID 861026): 1-14 [10.1155/2012/861026]

    Rashki, A., C. J. Kaskaoutis, C. J. Kaskaoutis, et al. C. J. Kaskaoutis, P. Eriksson, M. Qiang, and P. Gupta. 2012. "Dust storms and their horizontal dust loading in the Sistan region, Iran." Aeolian Research 5 51-62 [10.1016/j.aeolia.2011.12.001]

    Christopher, S., P. Gupta, B. Johnson, and J. Haywood. 2011. "Multi-sensor satellite remote sensing of dust aerosols over North Africa during GERBILS." Q.J.R. Meteorol. Soc. 137 (658): 1168-1178 [10.1002/qj.863]

    Haywood, B., T. Johnson, S. R. Osborne, et al. A. Baran, M. Brooks, S. F. Milton, J. Mulcahy, D. Walters, R. Allan, M. Woodage, A. Klaver, P. Formenti, H. E. Brindley, S. Christopher, and P. Gupta. 2011. "Motivation, rationale and key results from the GERBILS Saharan dust measurement campaign." Q.J.R. Meteorol. Soc. 137 (658): 1106-1116 [10.1002/qj.797]

    Gupta, P., and S. A. Christopher. 2009. "Particulate matter air quality assessment using integrated surface, satellite, and meteorological products: 2. A neural network approach." Journal of Geophysical Research: Atmospheres 114 (D20): [10.1029/2008JD011496]

    Gupta, P., and S. A. Christopher. 2009. "Particulate matter air quality assessment using integrated surface, satellite, and meteorological products: Multiple regression approach." JGR [DOI 10.1029/2008JD011496]

    Gupta, P., and S. A. Christopher. 2008. "An evaluation of Terra-MODIS sampling for monthly and annual particulate matter air quality assessment over the Southeastern United States." Atmospheric Environment 42 (26): [doi:10.1016/j.atmosenv.2008.04.044]

    Patadia, F., P. Gupta, S. A. Christopher, and J. S. Reid. 2008. "A Multisensor satellite-based assessment of biomass burning aerosol radiative impact over Amazonia." Journal of Geophysical Research 113 (D12): [10.1029/2007JD009486]

    Gupta, P., and S. A. Christopher. 2008. "Seven year particulate matter air quality assessment from surface and satellite measurements." Atmos. Chem. Phys. 8 [doi:10.5194/acp-8-3311-2008]

    Patadia, F., P. Gupta, and S. A. Christopher. 2008. "First observational estimates of global clear sky shortwave aerosol direct radiative effect over land." Geophys. Res. Lett 35 (4): L04810 [10.1029/2007GL032314]

    Gupta, P., F. Patadia, and S. A. Christopher. 2008. "Multisensor Data Product Fusion for Aerosol Research." IEEE Trans. Geosci. Remote Sensing 46 (5): 1407-1415 [10.1109/TGRS.2008.916087]

    Douglass, A. R., R. S. Stolarski, M. R. Schoeberl, et al. C. H. Jackman, P. Gupta, P. Newman, E. L. Fleming, J. E. Nielsen, and E. L. Fleming. 2008. "Relationship of loss, mean age of air and the distribution of CFCs to stratospheric circulation and implications for atmospheric lifetimes." J. Geophys. Res. 113 (D14): D14309 [10.1029/2007JD009575]

    Gupta, P., S. A. Christopher, M. A. Box, and G. A. Box. 2007. "Multi year satellite remote sensing of particulate matter air quality over Sydney, Australia." IJRS 28 (20): [10.1080/01431160701241738]

    Gupta, P., S. A. Christopher, J. Wang, et al. R. Gehrig, Y. C. Lee, and N. Kumar. 2006. "Satellite remote sensing of particulate matter and air quality assessment over global cities." Atmospheric Environment 40 (30): [doi:10.1016/j.atmosenv.2006.03.016]

                                                                                                                                                                                            
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