This is a past event.

Please join physics graduate students, Alan Larson and Mahsa Najafi for their presentations on Thursday, January 22 at 4 PM - Fisher Hall 139.

Alan Larson (Advisor: Ranjit Pati)

First-principles insights into structure–property relationships in engineered nanocomposites for nutrient delivery

Phosphorus (P) is an essential macronutrient for plant growth, yet nearly half of the agricultural soils worldwide are deficient in P. With an increase of food demand throughout the world, there is a need for the development of advanced fertilizer materials capable of delivering P efficiently and directly to the roots of the plants. To address this challenge, our experimental collaborators developed a novel nanocomposite slow-release fertilizer involving biochar (BC), attapulgite clay (ATP) and KH2PO4. In this work, we explained the observed slow release mechanism by investigating the underlying structure-property relationship using first principles Density Functional Theory (DFT). We carried out DFT calculations for two composite formulations and demonstrated that for certain composite formulations a slow release of phosphorus is possible.

Mahsa Najafi (Advisor: Petra Huentemeyer)

Improved Analysis of a TeV Halo Candidate from the HAWC observatory

TeV halos are extended regions of gamma-ray emission powered by high-energy electrons and positrons that escape from pulsar wind nebulae (PWNe) and diffuse through the surrounding medium. They are interesting because they suggest that particle transport near some pulsars can be much slower than expected, with important implications for how cosmic rays propagate through the Galaxy. In this talk, I present an updated study of a TeV halo candidate in the crowded region around PSR J1928+1746 using data from the High-Altitude Water Cherenkov (HAWC) Observatory. Compared to our earlier analysis, we now have substantially more exposure and improved event-selection cuts to better distinguish gamma-ray–like air showers from the far more numerous cosmic-ray background. This leads to cleaner sky maps and more stable source modeling. With these improvements, we can better disentangle overlapping TeV structures in the field and reduce confusion from nearby sources and diffuse Galactic emission. I will also show how the main extended emission associated with the TeV halo candidate remains remarkably stable in position, spectrum, and overall shape. This strengthens the case that the dominant component is a real, persistent physical source rather than an artifact of limited statistics or imperfect background modeling.