Western Kentucky University
Department of Physics and Astronomy

Colloquium

WKU Physics Majors & Graduate

Department of Physics and Astronomy
Western Kentucky University

"Research Projects Updates"

August 28, 2017 @ 4:00 pm in TCCW 201

Abstract

Khomidkhodzha Kholikov
"Graphene Quantum Dot Synthesis using Nanosecond Laser Pulses"

A biocompatible photodynamic therapy agent that generates a high amount of singlet oxygen with high water dispersibility and excellent photostability is desirable. In this work, a graphene-based biomaterial which is a promising alternative to standard photosensitizers was produced. Methylene blue was used as a reference photosensitizer. Bacteria deactivation by methylene blue was shown to be inhibited inside human blood due to protein binding. Graphene quantum dots (GQDs) were synthesized by irradiating benzene and nickel oxide mixture using nanosecond laser pulses. The productivity of GQDs was investigated by changing laser power density and wavelength with respect to time. Characterization results show that GQDs with size less than 10 nm were successfully obtained. The results of these studies can potentially be used to develop therapies for the eradication of pathogens in open wounds, burns, or skin cancers. New therapies for these conditions are particularly needed when antibiotic-resistant infections are present.

Saidjafarzoda Ilhom
"Laser Shock Wave Assisted Patterning on NiTi Shape Memory Alloy Surfaces"

Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50(at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30 % was observed. Recovery ratio decreased and saturated at about 15 % when the amount of time and thus the well depth was increased. Laser induced shock wave propagation inside the material was simulated and showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were observed.

Stacy Hancock
"Characterization and Threat Assessment of Eight Potentially Hazardous Near Earth Asteroids"

I have undertaken the study of eight potentially hazardous asteroids identified in conjunction with NASA’s OSIRIS REX Mission and observed via the Target Asteroid Project as my master’s thesis in the Homeland Security Sciences program. This study will include a characterization of these asteroids’ orbits and physical characteristics as well as a threat assessment. Using images obtained by the target asteroid project, I will determine the brightness of the asteroid as a function of time, known as a light curve. Analysis of the light curve will provide information on the rotation period of the asteroid and its size. The physical structure of the asteroid will be modeled using light curve inversion techniques. Knowledge of the size, structure and composition of the asteroid are critical parameters in assessing the severity of the threat an asteroid poses. Using the determined characteristics for each target asteroid, risk assessment and impact scenario modeling will be done to determine the effects of an impact event specific to each target.