Dissertation Defense Announcements

Mutations are a primary source of genetic variation and a major driving force in evolution by influencing survivability (fitness), genetic disease, and the development of complex traits such as antibiotic resistance. However, studying the mutation process is extremely challenging and time consuming, as most mutation rates lie between 1×10-11 to 1×10-9 mutations per site per generation. In my work, we have developed two major improvements in how we study the mutation process. First, we have developed a closed-system microfluidic platform that can be used to efficiently and rapidly measure mutation rates. This liquid-based platform overcomes many limitations of traditional growth methods, and can allow for the study of extremophiles or pathogens that cannot be grown on solid media. Second, we are studying mutations that drive collateral sensitivity (resistance from one antibiotic giving rise to sensitivity from another antibiotic) within Burkholderia multivorans patient isolates. Across 8 lineages involving 6 antibiotics, we identify mutations in Chemoreceptor CheD, DNA ligase D, and BON domain-containing proteins that are associated with antibiotic sensitivity. These proteins are known to repair double-stranded DNA breaks and control efflux pump function, providing a mechanistic approach for combatting antibiotic resistant strains using gene therapy.

In August 2019, The New York Times published what was said to be a “controversial” journalistic take on African American and American history. Written by Nikole Hannah-Jones, an awardee of the Pulitzer Prize and a MacArthur Genius Award, and her fellow journalists at The New York Times, The 1619 Project was intentionally published on the 400th anniversary of the arrival in Virginia of the first ships arriving in Virginia with enslaved Africans aboard (The New York Times, 2019). Although it has become one center of the United States political debate and rhetoric, the intent of The 1619 Project was not to further politicize the United States educational system. Rather, the intention was to present a compelling counternarrative to American history, but more importantly, African American history (The New York Times, 2019). However, because education within the United States is a politicized system, the work of Nikole Hannah-Jones and her colleagues has magnified the growing disconnect between a history of honest racial representation and its alignment with formal curriculum, standards, and education policy.
The purpose of this dissertation was to investigate how the formal social studies curriculum can become politicized by political actors and media. The New York Times’s The 1619 Project serves as a contemporary illustration of these dynamics. Through a multi-method approach using archival data and the Transcript: Ezra Klein Interviews Ta-Nehisi Coates and Nikole Hannah-Jones, the intent and media influence of The 1619 Project was examined situating the study within the theoretical frame of critical policy analysis using grounded theory methods to be analyzed through BlackCrit (Birk & Mills, 2015; Charmaz, 1996; Diem et al., 2014; Dumas & ross, 2016; King, 2018; Young & Diem, 2018).

Keywords: African American, The 1619 Project, representation, anti-Blackness, politics, political affiliation, education, Nikole Hannah-Jones, The New York Times, “controversial”

Antireflective structured surfaces (ARSS) are periodic, or random, distributions of three-dimensional nano-features fabricated directly on optical quality substrates, for the suppression of surface reflectivity from the dielectric boundary. Within the spectral band of efficient antireflective operation, the structures are sub-wavelength scale in crossectional diameter, and near-wavelength scale in height. As incident light passes from superstrate to substrate, the ARSS induce a synthetic index of refraction with a surface-average optical dielectric density, effectively matching the electromagnetic impedance on the surface separating the media, thus reducing Fresnel reflectivity. Published studies often model random ARSS as stratified homogenous dielectric layers, globally averaging the transverse feature distributions to a single optical index value per layer, and ignoring their distributed profiles.

In this work, the effects of pseudo-random deterministic transverse feature distributions within the ARSS and their antireflective properties were studied. Rigorous coupled wave analysis (RCWA) was used to compute the performance of periodic unit cell ARSS, superimposed on a binary-phase transmission grating as a function of the ARSS period, for TE and TM incident light polarization states, at normal angle of incidence. The results showed differences in performance between distinct ARSS distributions, despite their identical layer-averaged refractive index value. Sub-wavelength and near-wavelength scale unit-cell periodicities for ARSS with short autocorrelation lengths, show better overall anti-reflectivity performance, compared to less complicated feature distributions with comparable effective-permittivity layers. Numerical simulations for specific randomly distributed ARSS features correlated with anti-reflective performance efficiencies.

In parallel, the fabrication process of random anti-reflective structures (rARSS) was optimized for fused silica optical flats, and then applied to deterministic phase-diffusing diffractive optical elements (DOE) to suppress Fresnel reflections. The goal of the effort was to examine the effects of rARSS application on existing optical components. Four commercially available DOE, a 2D spot array generator, a 1D spot array, a controlled-angle illumination diffuser, and a discrete-phase profile diffractive lens, were used to investigate the effects of rARSS on 3-dimensional segmented-phase topographies. Three diffractive diffusers were measured over the entire equatorial plane of incidence using a scatterometer, to determine changes from the original design illumination pattern due to the presence of rARSS beyond a simple transmission enhancement. The diffractive lens was measured using a power detector and a beam profiler to compare the focal spots before and after addition of rARSS in transmission and reflection. The tests verified significant reduction of Fresnel reflections by the rARSS on the surface of the DOE, without altering their original performance efficiency. Finally, the non-deterministic scatter effects due to inherent roughness of the rARSS on segmented phase profiles was characterized by comparing scatterometer measurements of optical flats and near-wavelength scale binary-phase gratings. It is shown that scatter effects because of rARSS presence on optical flats and binary-phase gratings were negligible, indicating rARSS can be applied as an effective anti-reflection treatment to pre-fabricated optical surfaces with complex topography without degrading their performance.