Student Seminar at the Department of Physics and Applied Physics

Saba Fajors, a sophomore pursuing a BS in physics, will discuss, “Experimental Investigation of Viscous Damping Effects on Topologically Protected Edge Modes in a Macroscopic SSH Lattice.”

Abstract
In 2009, Dr. Prodan–theoretically–showed that the protein lattice forming microtubules supports a class of vibrational modes localized at its ends that are topologically protected, immune to the disorder that would ordinarily scatter them out of existence. Because microtubule growth and collapse is thought to originate at these same ends, and because this dynamic instability is the target of chemotherapy drugs such as Taxol, the proposal that topology gates the switch is of direct biological interest. That proof, however, assumed a lossless lattice; a real microtubule sits in viscous, crowded cytoplasm, and whether topological protection survives viscous drag has never been tested. This project addresses that gap with a macroscopic analog: an 11-resonator Su-Schrieffer-Heeger (SSH) chain built from matched, magnetically coupled spinners with alternating strong-weak coupling, whose geometry was first modeled in COMSOL Multiphysics. A Python-programmed video-tracking/analysis system takes the resonator’s position, oscillation frequency, and decay rate from recorded motion. After early attempts to seal the lattice inside a viscous fluid proved mechanically unrealistic, the experiment was redesigned around a small vane on a single arm dipping into an open cup of a viscous substance, a method that isolates viscous drag as the only variable change, with no contact and no seal. Ongoing work is to test against various viscous substances to test whether the protected edge mode maintains its frequency as drag increases, cross-validating against a PASCO string vibrator on the same resonator.

Gabriella Freire, a senior majoring in physics will discuss,”Particulate Matter (PM2.5) Collection at Varying Altitudes via Weather Balloon in the Bronx NY.”

Abstract
Particulate matter (PM2.5) is an air pollutant associated with significant environmental and health impacts, including asthma and cardiovascular disease. To investigate the relationship between altitude and PM2.5 concentration, a moored weather balloon system and a Raspberry Pi-based sensor package were developed to collect air quality data at altitudes up to 150 feet in the Fordham neighborhood of the Bronx. The balloon platform consisted of a 5.5 foot cloudbuster, three tether lines, a rapid deflation line, a payload package, and a reeling base. The sensor package integrated a PMS5003 particulate matter sensor, a BME280 environmental sensor, and an Adafruit GPS HAT encoded into a Python script logged data to a CSV file for subsequent analysis of altitude and concentration relationships. Data was collected over multiple days and results indicated little correlation between altitude and PM2.5 concentration levels within the 150 foot range tested. These findings suggest that altitude may be disregarded as a significant contributing factor in future low- altitude air quality studies, allowing future projects to prioritize spatial (longitudinal and latitudinal) data collection instead. Additional trials using the weather balloon system are planned to further validate this conclusion before altitude is fully excluded as a variable of interest.