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Thesis advisor: Heather T. Rowan-Kenyon / Rural undergraduates lag behind urban and suburban undergraduates across many measures of college success, even though they graduate from high school at a higher rate. While a small but growing body of research literature addresses the challenges and barriers rural students face during the college process, few, if any, studies have focused specifically on the experience of rural undergraduates who withdraw from college before completing a degree.This qualitative phenomenological study examines the experiences of rural, low-income, first-in-family undergraduates who stop out of college. Study participants (n=13) attended high school in different rural communities and geographic regions across the United States. After participating in an Upward Bound program during high school, they each enrolled in a two- or four-year, undergraduate degree program at an accredited, non-profit college or university and then withdrew prior to completing a degree. Following in the tradition of Edmund Husserl (1859-1938) and using the framework provided by Clark Moustakas (1994), I engaged study participants in open ended, semi-structured interviews. After those conversations, participants submitted independently recorded voice memos about their experience stopping out of college. The rural backgrounds of study participants manifested in many aspects of how and what they experienced when they withdrew from college. The phenomenon was described as an intense and devastating period of time, characterized by feelings of failure, shame, confusion, and disappointment. The distinct influence of rural families, communities, and schools shaped participants’ decisions before, during, and after their time at college. While the reasons students withdrew varied widely and may be similar to those of non-rural students, all participants perceived their rural background as deeply implicated in the stop-out experience. This study offers a new orientation on the topic of college stop-out among rural undergraduates and presents a working persistence model for this underserved student group. The three theoretical perspectives presented in this study – transcendental phenomenology, ecological systems theory, and community cultural wealth – expose broader meaning about both the objective and subjective qualities of the stop-out experience, adding a depth to findings that has broad implications for scholars and practitioners. This study concludes with practical insights for educators, policymakers, and institutions that serve rural undergraduates. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Lynch School of Education. / Discipline: Educational Leadership and Higher Education.

Historically, urban high school students encounter socioeconomic, educational, and systematic barriers in pursuit of college acceptance and admissions (VanTassel-Baska and Willis, 1987; Freedle, 2003; Dixon-Roman, Everson, and McArdle, 2013). These same hurdles are ever present for these students in their enrollment in SAT test then the SAT scores. Furthermore, urban students with learning and/or language differences are further disadvantaged by compounding variables of socioeconomics, disability, and access to resources. Given the significance of SAT scores in college admission, it is imperative that disadvantaged students from urban communities are provided proper support, guidance and instruction thought non-profit community organization that serve as college access conduits. This research study examine SAT Verbal prep offered through the Upward Bound program. SAT Verbal was offered through two instructional modes: teacher-led lecture or student-authored multimedia instruction. SAT Verbal instruction type was compared with a small sampling of students enrolled in Dual Enrollment to determine which SAT instruction increased scores beyond exposure to college level coursework. Three different groups were used in this pre-posttest design that utilized a combination of unique randomization and non-randomized group placements (n=101). Pre and posttest were analyzed with ANCOVAs to evaluate mean changes across the groups. Results indicate that students participating in high frequency academic vocabulary CAPs experienced a highly statistically signification casual effect of increasing scores on SAT Composite(p<.00) and SAT Verbal scores (p<.00). These results are even more pronounced in student groups with learning or language differences. Diverse students enrolled in multimedia instruction saw their SAT Composite scores increases (ELL=5.34%, IEP=18.12%) and SAT Verbal scores (ELL-3.67%, IEP 12.88%). These results support use of CAPS to address language, learning, access, and socio-economic issues that hinder urban students from high achievement on SAT, and ultimately college admission. / Special Education

<p> Non-homologous end joining (NHEJ) is the predominant mode of DNA double strand break (DSB) repair pathway in mammalian cells. At the heart of this repair pathway is Xrcc4-DNA ligase IV complex, which mediates ligation of the broken DNA strands. The C-terminal tandem BRCT repeats of human DNA ligase IV spanning residues 654-911 in complex with the functional fragment of Xrcc4 comprised of residues 1-203 were crystallized by the hanging drop vapour diffusion method at 20°C. Generation of single, well-packed, diffraction quality crystals suitable for structure determination involved usage of an Xrcc4 point mutant (A60E). Arriving at the crystallization condition included optimization of pH, variation of the precipitant concentration, investigation of the effects of small molecules, and alteration of the amount of crystal seed used as initial nuclei. A Crystal of selenomethionine-derived protein complex was grown using the above optimization steps and diffracted to 2.4 A resolution. Data processing revealed that the crystal belonged to space group P1 with unit cell dimensions a= 67.33 b = 86.00 c = 111.52; a= 67.37 ~ = 83.00 y = 74.56. The crystal structure of Xrcc4-DNA ligase IV complex was solved by single-wavelength anomalous diffraction using data collected at a wavelength of 0.9785A corresponding to peak energy. </p> <p> The structure maintains a 2:1 stoichiometry of Xrcc4 to the C-terminal domain of DNA ligase IV. The structure of the complex not only confirms the overall novel mode of interaction first observed in the 3.9 A structure of the yeast ortholog liflp-lig4p complex, but it also discloses additional key features such as the DNA binding surface of the complex and the striking conformational changes occurring within Xrcc4 upon interaction with DNA ligase IV. Together, the structural information procured forms an important basis for a better understanding of the mechanism involved in the NHEJ repair pathway. </p> / Thesis / Master of Science (MSc)

In the search for molecular species in the interstellar medium and extraterrestrial planetary atmospheres, theoretical methods continue to be an invaluable tool to astronomically minded chemists. Using state-of-the art methods, this doctoral work characterizes the electronically excited states of interstellar radicals, cations, and even rare anions and also predicts the gas phase fundamental vibrational frequencies of the cis and trans-HOCO radicals, as well as the cis-HOCO anion. First, open-shell coupled cluster methods of singles and doubles (CCSD) and singles and doubles with triples-inclusion (CC3) are tested on the C₂H and C₄H radicals. The significant double-excitation character, as well as the quartet multiplicity of some states yields inaccurate excitation energies and large spin contamination with CCSD. CC3 somewhat improves this for select states, but discrepancies between CC and multireference results for certain states exist and likely arise from the lack of spin adaptation in conventional spin-orbital CC. Next, coupled-cluster methods predict the presence of an excited state of the closed-shell allyl cation and its related H₂CCCHCH₂⁺ cousin at 443 nm near an unidentified laboratory peak at 442.9 nm which is also close to one of the largest unattributed interstellar absorption features. Additionally, the dipole moments, electron binding energies, and excited states of neutral radicals and corresponding closed-shell anions of interstellar interest are also computed. These are calibrated against experimental data for CH₂CN⁻ and CH₂CHO⁻. Since coupled cluster theory closely reproduces the known experimental data, dipole-bound excited states for eight previously unknown anions are predicted: CH2SiN⁻ , SiH₂CN⁻, CH₂SiHO⁻, SiN⁻, CCOH⁻, HCCO⁻, SiCCN⁻, and SiNC⁻. In addition, we predict the existence of one rare valence-bound excited state of CH₂SiN⁻ and also SiCCN⁻ as well as even rarer two valence-bound states of CCSiN⁻. Lastly, the reaction of CO + OH and its transient potential intermediate, the HOCO radical, may be responsible for the regeneration of CO₂ in the Martian atmosphere, but past spectroscopic observations have not produced a full gas-phase set of the fundamental vibrational frequencies of the HOCO radical. Using established, highly-accurate quantum chemical coupled cluster tech- niques and quartic force fields, all six fundamental vibrational frequencies for 1 ²A′ cis and trans-HOCO and 1 ¹A′ cis-HOCO⁻ are computed in the gas phase. / Ph. D.

This work addresses two primary topics related to vibrations in structures. The first topic is the use of a spatially distributed sensor network for localization of vibration events. I use a received signal strength (RSS) framework that presumes exponential energy decay with distance to the source. I derive the Cramér-Rao bound (CRB) for this parameter estimation problem, with the unknown parameters being source location, source intensity, and the energy dissipation rate. In this framework, I show that the CRB matches the variance of maximum likelihood estimators (MLEs) in more computationally expensive Monte Carlo trials. I also compare the CRB to the results of physical experiments to test the power of the CRB to predict spatial areas where MLEs show practical evidence of being ill-conditioned. Supported by this evidence, I recommend the CRB as a simple measure of localization accuracy, which may be used to optimize sensor layouts before installation. I demonstrate how this numerical optimization may be performed for some regions of interest with simple geometries. The second topic investigates modal vibrations of multi-body structures built from simple one-dimensional elements, with networks of elastic strings as the primary example. I introduce a method of using a nonlinear eigenvalue problem (NLEVP) to express boundary conditions of the vibrating elements so that the (infinitely many) eigenvalues of the full structure are the eigenvalues of the finite-dimensional NLEVP. The mode shapes of the structure can then be recovered in analytic form (not as a discretization) from the corresponding eigenvectors of the NLEVP. I show some advantages of this method over dynamic stiffness matrices, which is another NLEVP framework for modal analysis. In numerical experiments, I test several contour integration solvers for NLEVPs on sample problems generated from string networks. / Doctor of Philosophy / This work deals with two primary topics related to vibrations in structures. The first topic is the use of vibration sensors to detect movement or impact and to estimate the location of the detected event. Sensors that are close to the event will record a larger amount of energy than the sensors that are farther away, so comparing the signals of several sensors can approximately establish the event location. In this way, vibration sensors might be used to monitor activity in a building without the use of intrusive cameras. The accuracy of location estimates can be greatly affected by the relative positions of the sensors and the event. Generally, location estimates tend to be most accurate if the sensors closely surround the event, and less accurate if the event is outside of the sensor zone. These principles are useful, but not precise. Given a framework for how event energy and noise are picked up by the sensors, the Cramér-Rao bound (CRB) is a formula for the achievable accuracy of location estimates. I demonstrate that the CRB is usefully similar to the location estimate accuracy from experimental data collected from a volunteer walking through a sensor-rigged hallway. I then show how CRB computations may be used to find an optimal arrangement of sensors. The match between the CRB and the accuracy of the experiments suggests that the sensor layout that optimizes the CRB will also provide accurate location estimates in a real building. The other main topic is how the vibrations of a structure can be understood through the structure's natural vibration frequencies and corresponding vibration shapes, called the "modes" of the structure. I connect vibration modes to the abstract framework of "nonlinear eigenvalue problems" (NLEVPs). An NLEVP is a square matrix-valued function for which one wants to find the inputs that make the matrix singular. But these singular matrices are usually isolated---% distributed among the infinitely many matrices of the NLEVP in places that are difficult to predict. After discussing NLEVPs in general and some methods for solving them, I show how the vibration modes of certain structures can be represented by the solutions of NLEVPs. The structures I analyze are multi-body structures that are made of simple interconnected pieces, such as elastic strings strung together into a spider web. Once a multi-body structure has been cast into the NLEVP form, an NLEVP solver can be used to find the vibration modes. Finally, I demonstrate that this method can be computationally faster than many traditional modal analysis techniques.

Information Technology (IT) jobs are in demand in the United States and rural Appalachian communities are attracting IT businesses. The need to fill IT jobs creates a workforce opportunity for these communities where students have limited access to academic and career resources. The Upward Bound and Talent Search programs respond to the academic and career needs of disadvantaged students and aim to educate students about high skills jobs but little is known about interest in IT careers among middle and high school students in rural Appalachia. This study validates models of IT career interest and parental support of IT careers in girls and boys enrolled in Upward Bound or Talent Search in rural communities in Virginia using the theoretical framework of self-authorship. The theory of self-authorship explores the development of meaning-making in individuals and offers a context-specific way to study interest in IT careers. Results indicate interest in IT careers but the path to IT career interest is different among girls and boys. Girls are relying on others for career advice more often than boys and there is direct association between the information sources and interest in IT careers. Parental support is important in IT career interest for both girls and boys. Other important variables indicating an interest in IT careers are computer use and positive attitudes toward IT workers. Receiving information from sources such as parents, teachers, counselors, and friends is especially important to girls. Findings from this study can be used to inform practices and policies for Upward Bound and Talent Search. / Ph. D.