Knowledge of atmospheric particle size distributions (PSDs) is important for understanding a variety of atmospheric components, such as characteristics of aerosol light scattering and absorption, influence of aerosol chemical components in aerosol optical properties. Here, an analytical method has been implied to size segregated aerosol particles of the continental, rural, urban and marine region for finding the variability of aerosol size distribution at different background locations. Different techniques are used for measuring the absorption and scattering of aerosol particles and in this study measurement of aerosol absorption coefficient is explained based on filter techniques, in which size segregated aerosol particles of diameters less than diameter of 1 micrometer and 10 micrometer are collected by using a two-stage high flow non-rotating Micro-Orifice Uniform Cascade Impactor (MOUDI). These filter samples are used for reflectance techniques where monochromatic and integrating reflecting spheres are used for measuring the light absorption coefficient. The absorption coefficient can be used to determine the single scattering albedo (SSA) and are used to specify the chemical components of aerosol particles. SSA of aerosol particles different background locations are presented in this study by using previously published research data in Peer Reviewed Journals. Comparing SSA with size segregated particle concentration, seasonal variability of aerosol optical properties of different locations of different surroundings are investigated for local aerosol source.
*Rudra Aryal was born in Palpa. He has received his Ph.D. degree in Physics from the University of Miami, Florida, USA and his M.Sc. and B.Sc. degrees in Physics from Tribhuvan University, Kritipur and Trichandra College Kathmandu, Nepal. He is a former joint secretary of Nepal Physical Society (2000-2002/ 2002-2004). Currently, he is Professor of Physics at Franklin Pierce University, New Hampshire USA. His research focuses on air pollution especially on the interaction of solar radiation with surface level and column integrated atmospheric pollutant (aerosol) particles.
Date: 14 January, 2019
29 Poush, 2076
The need for efficient energy utilization is driving research to harvest waste-heat, which is ubiquitous, abundant, and free. Thermal harvesting is a promising method for capturing freely available heat and converting it to a more usable form, such as electrical energy. Thermal harvesting for low power electronic devices using ferroelectric materials is one of the emerging areas of research because they possess spontaneous polarization and exhibit excellent piezoelectric as well as pyroelectric coefficients. These materials are unique as they only sense time-dependent temperature change to generate electric power. We have grown lead-free BaZr0.2Ti0.8O3 (BZT)/ Ba0.7Ca0.3TiO3 (BCT) epitaxial heterostructures on SrRuO3 (SRO) buffered SrTiO3 (STO) single crystal substrate by optimized pulsed laser deposition (PLD) technique and studied the structural, dielectric, ferroelectric, and pyroelectric properties. Our multilayer heterostructure exhibits very low leakage current and well-saturated polarization versus electric field (P-E) loops with high saturation and low remnant polarization. Finally, we have developed a thin-film device, which demonstrates huge pyroelectric current in response to small temperature fluctuation. This finding suggests that the lead-free relaxor-ferroelectric thin films may be competitive with thermoelectric materials for low-grade thermal harvesting.
*Amrit Sharma is a PhD. candidate at Material Science and Engineering Department of Norfolk State University, Norfolk, Virginia - USA
Date: 02 January, 2019
17 Poush, 2076
Recent neuroimaging studies on musical improvisation have identified brain regions and networks involved during musical improvisation, which provides an excellent paradigm for understanding human creative cognition. Despite some previous studies on structural brain differences between musician and nonmusician, whether and how the underlying white matter microstructure reflects the neural activity and connectivity pattern is not clearly understood. In this study, we investigated the relationship between the white matter diffusion properties and functional connectivity from functional and diffusion magnetic resonance imaging (MRI) of 20 advanced level jazz improvisers. We found that musical improvisation compared with prelearned melody is characterisedby higher regional activity in left frontal and motor areas, including Broca's area, dorsolateral prefrontal cortex, lateral premotor cortex, suppplementary motor area and right cerebellum, and lower functional connectivity in number and strength among these regions. We further investigated the white matter diffusion properties, especially the anisotropic measures for fibers crossing brain areas that showed higher activation during musical improvisation and compared the findings with non-musicians. We observed the advanced jazz improvisers had higher quantitative anisotropy (QA) for fiber crossing in brain areas and fiber tracts connecting those brain areas. These findings suggest the variation in white matter properties has behavioral consequences that reflect the neural basis of creative expertise, especially the frontal-motor connectivity.
*Kiran Dhakal is a PhD. candidate and Brain & Behavior Fellow at neurophysics lab of Georgia State University, USA.
Date: 16 December, 2019
30 Mangsir, 2076