Publications

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R&D Areas/Projects

• Atmospheric aerosols and nanoparticles: Modification of regional air quality, the radiation balance and climate. Atmospheric aerosols are gaseous dispersions of ultrafine particles (black carbon, organic compounds, ions, minerals), which interact with radiation, and modify cloud structure and precipitation patterns. Recent observational studies conducted under ISRO-Geosphere Biosphere Program point to large spatial and temporal variability of surface and elevated aerosols over the Indian subcontinent, the contribution of both local emissions and long-range transport, especially of dust, and regionally specific aerosol chemistry, potentially mediated by dust aerosols. We conduct atmospheric simulation studies with a state-of-the-science model: the global general circulation model of the Laboratoire de Meteorologie Dynamique (LMD-ZT). The models include a detailed treatment of gas and aerosol chemistry, deposition and wet removal processes. Emissions for these models have been developed in our group's emissions modelling activity and reflect fuel composition, technology use and pollution control in current practice. Scientific issues being addressed include the following:

   

• 1.Role of seasonal meteorology in modulating variations in aerosol spatial and temporal distributions.
• 2.Influence of long-range transport on regional aerosol loadings over India.
• 3.Atmospheric chemical state in response to emission perturbations.
• 4.Radiative and climate effects of aerosols, including alteration in rainfall patterns, using measured regionally representative aerosol optical parameters.
• Matrix factorization and trajectory based receptor models for air pollution source identification Identification of sources and geographical regions contributing to pollutants over large spatial scales is mathematically challenging. Receptor models like positive matrix factorization (PMF) cast pollutant source-receptor relationships as X = GF + E, where X is a measured pollutant elemental concentration matrix, F is the source composition matrix or relative abundance of different pollutants in emissions from given sources, and G is the source contribution matrix or amount of material contributed by each source. Optimization of the solution uses matrix rotations and target factor shaping approaches. Identification of probable aerosol source locations or transport pathways using ensembles of air back trajectories, is done through calculation of a potential source contribution function (PSCF). PMF and PSCF calculations are being applied to pollutant time-series field data from recent measurement campaigns in the Indian regions, to understand regional source-receptor relationships. Campaigns include the ISRO-Geosphere Biosphere Program based land campaign to study aerosols, trace gases and their influence on fog formation during wintertime in the Indo-Gangetic plain and shipborne campaigns in the Arabian Sea and Bay of Bengal.
• Aerosol routes for the synthesis and pulmonary delivery of nanoparticle drugs. The direct administration of drugs into the lung through inhalation therapy has advantages including immediate effect and smaller dose requirement than oral administration. Using nanosized vesicles synthesized from phospholipids as drug encapsulating agents, offers the advantage of biocompatibility with the lung surfactant. Design of aerosolization systems must address prevention of structural damage to such particles to preserve their drug payload. Engineering particles with tailored aerodynamic size distribution is needed to target deposition with high efficiency in the alveolar lung. Approaches include the following:
• 1.Studies of the stability and size distribution of lipid vesicles synthesized from a variety of precursors, examining process conditions like pH, stabilizing agents and others, which affect vesicle size and wall strength. Evaluation of suitability for drug encapsulation.
• 2.Identification of factors leading to structure alteration and rupture of vesicles during aerosolization using nebulizer technologies. Synthesis of vesicles with enhanced stability.
• 3.Characterization methods include aerodynamic size distribution measurements using inertial impaction and electrical mobility classification and laser scattering techniques, and imaging with TEM / cryo-TEM and confocal microscopy.
• 4.Design of systems for inhalation delivery based on electrospray and vibrating orifice aerosol generation technologies.
• 5.Computational modelling is planned of the transport and deposition of drug aerosols through aerosol delivery devices and the human lung.

PhD TA Topics