Star clusters have been incredibly useful tools for studying the history of the Milky Way because they allow us to determine relative ages based on their chemical abundances. However, most stars are not in clusters, and current methods used to determine ages for individual stars produce substantial uncertainties. A new age method enabled by the precise photometry data of the NASA Kepler satellite is asteroseismology. Asteroseismology allows us to probe the internal structure of stars that are affected by age and composition. This research aims to calibrate the relationships between age, chemical abundances, and asteroseismology by analyzing data of stars in star clusters, which provide an independent measure of the stars' ages. This project aims to expand upon the currently used age and chemical abundance range and triple the number of open star clusters used to calibrate the asteroseismic age-mass-chemical abundance relation. We have combined asteroseismology data for stars in clusters within the Kepler 2 campaign fields with uniformly determined follow-up spectroscopic abundances from observations from the MMT.

Micro- and nano-scale ZnO particles are known to inhibit the growth of bacteria. Though this phenomenon has been vigorously studied, the fundamental mechanisms driving this action remain unknown. Mechanisms proposed by other studies include: the production of reactive oxide species, release of zinc ions, damage to the cell wall due to interactions with ZnO surfaces, and the inhibition of enzymes. ZnO surface defects serve as reaction sites for the processes driving these bactericidal interactions. Additionally, through MIC assays, we found antibacterial action of microparticles to be comparable to that of nanoscale particles. This confirms that antibacterial action of ZnO is rooted in surface-surface interactions between bacteria and ZnO. Therefore, our studies focus on ZnO surface charge dynamics and surface defects using surface photovoltage methods. Surface photovoltage experiments were performed on commercial grade ZnO nanoparticles and hydrothermally grown ZnO microcrystals in conjunction with antibacterial assays to elucidate the surface and near-surface charge dynamics associated with antibacterial processes of the ZnO surfaces.

With the advent of graphene, there has been an interest in utilizing this material and its derivative, graphene oxide (GO) for novel applications in nanodevices such as bio and gas sensors, solid-state supercapacitors and solar cells. Although GO exhibits lower conductivity and structural stability, it possesses an energy band gap that enables fluorescence emission in the visible/near infrared leading to a plethora of optoelectronic applications. In order to allow fine-tuning of its optical properties in the device geometry, new physical techniques are required that, unlike existing chemical approaches, yield substantial alteration of GO structure. Such a desired new technique is one that is electronically controlled and leads to reversible changes in GO optoelectronic properties. In this work, we for the first time investigate the methods to controllably alter the optical response of GO with the electric field and provide theoretical modeling of the electric field-induced changes. Field-dependent GO emission is studied in bulk GO/polyvinylpyrrolidone films with up to 6% reversible decrease under 1.6 V µm−1 electric fields. On an individual flake level, a more substantial over 50% quenching is achieved for select GO flakes in a polymeric matrix between interdigitated microelectrodes subject to two orders of magnitude higher fields. This effect is modeled on a single exciton level by utilizing Wentzel, Kremer, and Brillouin approximation for electron escape from the exciton potential well. In an aqueous suspension at low fields, GO flakes exhibit electrophoretic migration, indicating a degree of charge separation and a possibility of manipulating GO materials on a single-flake level to assemble electric field-controlled microelectronics. As a result of this work, we suggest the potential of varying the optical and electronic properties of GO via the electric field for the advancement and control over its optoelectronic device applications.

The Smith Cloud is a fast-travelling gas cloud that is currently hurtling towards the Milky Way galaxy at about 170,000 miles per hour. If the cloud is able to reach the Galactic plane, it has the potential to supply the Milky Way with at least 2 million suns worth of gas. This gas can be used to make new stars, planets, and even meatballs. In this project, we use observations taken with the Hubble Space Telescope and the Green Bank Telescope. We fit our spectroscopic observations with line profiles to quantify the amount of gas and its motions. We then take measurements of the low- and high-ionization species of two small cloud fragments that lie adjacent to the main body of this large gas cloud. This enables us to constrain the processes that impact the Smith Cloud as it traverses the Galactic halo. Our investigation could provide great insight on how galaxies capture the gas that they use to form stars and planets.

Intrinsic and extrinsic motivation satisfy biological needs or desires. Behavior that is intrinsically motivated is not followed by any apparent reward, except for the behavior itself. Behavior that is extrinsically motivated is followed a separate, observable reward. The overjustification hypothesis states that after engaging in behavior as a means to an extrinsic reward, there will be a reduction in one’s intrinsic motivation to engage the behavior. The current study observed whether the overjusitification effect occurs in rats when using lever pressing as a measure of intrinsic motivation. For all rats, intrinsic motivation was measured in Phase 1 by the number of lever presses made by each rat in the absence of any observable reward. In Phase 2, one group continued to lever press without reward (Control), while the other group received a sucrose pellet (extrinsic reward) for each lever press. Lever pressing in the absence of reward (intrinsically motivated) was again measured in Phase 3. The extrinsic reward group emitted more lever pressing in the sessions at the start of Phase 3. Lever pressing decreased thereafter, but stabilized at a higher rate than the control group. The groups were then switched before Phase 2 was repeated. The overjustification effect was not observed in our study, but rather, reinforcement protected the response from habituation.