Thesis advisor: Margaret . Lombe / The present study is situated at the intersection of the topics of migration and mothering; it seeks to examine the complexities around mothering in conditions of violence, precariousness, institutional neglect and mobility across borders. In particular, it documents the pre-migration, transit and post-migration experiences of 17 Central American mothers who have crossed the US-Mexico border with their children since 2014, and are resettling in the Boston area while they wait resolution of their asylum claims. By analyzing participants’ narratives, collected through in depth semi-structured interviews, the study explores (a) mothers’ exposure to traumatic events and human rights abuses transnationally; (b) mothers’ practices to survive and support their children under difficult conditions; (c) and the association of maternal experiences and practices with maternal mental health. The study documents how the unjust conditions in which these mothers parent their children—violence, precariousness and institutional neglect— contribute to difficult maternal practices—such as decisions to leave children behind or to risk taking children across borders—and unjust mental health outcomes for mothers. Some mothers in the study reported high levels of anxiety, depression and PTSD, related to contextual experiences and challenging maternal practices. Based on these findings and feminist theories, the study presents a gender sensitive theoretical framework to guide scholarship and practice with asylum-seeking mothers traveling with some of their children across borders. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Social Work. / Discipline: Social Work.

Thesis advisor: C. Patrick Proctor / Schools, districts, and states are at a time of transition from the federal No Child Left Behind Act (NCLB) to The Every Student Succeeds Act (ESSA) and this change comes alongside evolving state policy landscapes. Since NCLB and the epoch of English-only education in Massachusetts, which ended after the passage of the Language Opportunity for Our Kids (LOOK) Act in 2017, have been shown to have a primarily negative impact on emergent bilingual students, a historically marginalized group of learners, there is a need for educators and researchers to understand how educators are comprehending and responding to policy changes. Yet processes of policy interpretation and implementation are often not straightforward and many factors from the location of an organization to an individual’s role, connections, and prior professional experiences (Burch & Spillane, 2005; Spillane, 1998) can impact policy understandings and implementation. The purpose of this qualitative dissertation was to understand how educational leaders interpreted and responded to ESSA and the LOOK Act in Massachusetts. Utilizing sensemaking theory as a theoretical framework (Spillane, Reiser, & Reimer, 2002), analysis of 17 participant interviews as well as state documents demonstrated that district, state, school, and organizational leaders were optimistic about the educational future of bilingual children in Massachusetts. They viewed the LOOK Act as offering needed flexibility for designing educational programs, as better aligning with participants’ beliefs about bilingualism and language learning, and as potentially facilitating the increased engagement of bilingual families as stakeholders with a voice. Educational leaders understood ESSA in relation to how they understood NCLB. They also viewed ESSA primarily as a compliance mandate. Participants responded to ESSA and LOOK by defending their intentional focus on the immediate: the policies, initiatives, and practices that aligned with their beliefs about what is best for bilingual students. These priorities included reconceptualizing programs of education for bilingual students and launching English Learner Parent Advisory Councils, both made possible by the LOOK Act, as well as hiring and retaining equity-minded district leaders, advocating at the state and district levels around funding structures, building teacher capacity to teach emergent bilingual students, developing multiple pathways for children, and shifting belief systems around bilingualism and bilingual children. Developing understandings of how educators interpret and respond to ESSA and LOOK can further inform educators’ crafting of policies and programs that can benefit bilingual children. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Lynch School of Education. / Discipline: Teacher Education, Special Education, Curriculum and Instruction.

Three-dimensional (3D) structure of a protein is essential as the guidance of structure-based drug dis-covery. To achieve robust homology modeling with atomic-level accuracy, reliable loop predictions are required. Here, a novel hierarchical protocol of Protein Local Optimization Program (PLOP) is designed to produce sub-2 angstrom predictions on loop regions in homology modeling. Dramatic improvements in both speed and accuracy have been realized with implementation of special-designed clustering and adaptive loop closure algorithm. Four prediction rounds are designed for homology modeling as the high-level protocol of PLOP, which allows latter rounds employ the educated guess of backbone atom positions and hydrogen bonding information inherited from the previous rounds, contributing to additional prediction accuracy. The success of PLOP has been demonstrated with four different data sets, mainly concen-trating on homology modeling of H3 loops of antibodies. GPU-accelerated sampling algorithm and deep learning models are implemented, which are able to produce promising predictions as input templates for PLOP in the context of homology modeling.

Meiotic recombination is a fundamental genetic process in all sexually reproducing eukaryotes, ultimately responsible for the generation of new combinations of alleles upon which natural selection can act. It begins with the formation of programmed double stranded breaks along the genome, and ends with their repair as non-crossover or crossover recombination events. The localization of such events along the genome has important evolutionary consequences for genome structure, base composition, patterns of genetic diversity, linkage disequilibrium and introgression, along the genome, as well as in the evolution of post-zygotic hybrid sterility and speciation. Understanding how meiotic recombination events are localized is thus crucial to the proper interpretation of observed genetic variation, and to the field of population genetics as a whole. However, little is known about how most species localize recombination events. While some species localize meiotic recombination events fairly evenly along the genome (e.g., Caenorhabditis elegans or Drosophila), most species studied to date, including all yeasts, plants and vertebrates, localize the vast majority of meiotic recombination events to narrow intervals of the genome known as recombination hotspots. Within such species, there appear to be at least two general mechanisms underlying the localization of hotspots. First, in many species, including baker’s yeast, canids, birds, and plants, the vast majority of hotspots are found in close proximity with promoter-like features of the genome, such as transcriptional start sites and CpG-islands. Recombination landscapes in these species tend to be highly conserved between closely related species. Second, in mice, primates and cattle, the vast majority of hotspots are found away from promoter-like features of the genome, and at sites bound by the PRDM9 protein, which has a rapidly evolving DNA-binding specificity. Concordantly, the recombination landscapes in these species tends to be rapidly evolving. The aim of Chapter 2 of this dissertation is to characterize the distribution of mechanisms across vertebrates indirectly, by leveraging what is known about their genetic and molecular underpinnings. In particular, I consider what is known about the molecular mechanisms and evolutionary consequences of using PRDM9 to localize recombination events, and attempt to infer which vertebrate species are or are not likely to be using PRDM9 in an analogous manner. I find that PRDM9 has been lost repeatedly within vertebrates, and, moreover, that many species carry partial PRDM9 orthologs lacking one or more feature believed to be important for its role in recombination. In Chapter 3, I demonstrate that swordtail fish, which have such a partial PRDM9 ortholog, do not use PRDM9 to localize recombination events. Instead, they use promoter-like features of the genome, similar to species lacking PRDM9 altogether. This work suggests that only species carrying complete PRDM9 orthologs are likely to use them to localize recombination events, and that upon the partial or complete loss of PRDM9, species typically default to the use of promoter-like features. Beyond more immediately practical insight, understanding the phylogenetic distribution of mechanisms by which meiotic recombination events are localized along the genome will shed light on why different species employ different mechanisms. The repeated losses of PRDM9-directed recombination across vertebrates suggests that selective pressures are not always strong enough to justify the evolutionary maintenance of PRDM9. Notably, theory suggests that PRDM9’s DNA-binding specificity has to be continually evolving in order for it to localize recombination events to hotspots. This is a consequence of gene conversion acting to remove PRDM9 binding sites from the population over time. Models have been proposed in which selection favors younger PRDM9 alleles because their binding sites have experienced less erosion due to gene conversion. Nonetheless, it has remained unclear how the loss of PRDM9 binding sites might cause a reduction in fitness, principally because it has remained unclear what the evolutionary benefit of having hotspots is more generally. Recently, however, a number of studies investigating the role of PRDM9 in mediating hybrid sterility in certain crosses of musculus subspecies have implicated the erosion of its binding sites in this process. In particular, the lineage specific erosion of PRDM9 binding sites causes, in the F1 generation, the PRDM9 alleles from each parental lineage to bind primarily to the non-parental genetic background, where its binding sites have not yet been eroded. These studies suggest that there is a benefit to the symmetric binding of PRDM9 across homologous chromosomes, and that fitness is reduced as a consequence of asymmetry in PRDM9 binding. In Chapter 4 of this dissertation I develop a population genetics based model of the co-evolution of PRDM9 and its binding sites taking into consideration these recent findings. In particular, I model competition between PRDM9 binding sites and define fitness as a function of PRDM9 binding symmetry. This model demonstrates that PRDM9 binding symmetry will decrease over time in randomly mating populations, and that selection for symmetric binding is sufficient to drive the rapid turnover of PRDM9 alleles. Importantly, the requirement for symmetry in this model shapes the recombination landscape by favoring highly skewed binding distributions. This model thus provides theoretical support for the hypothesis that a requirement for symmetry might underlie the evolutionary advantage of recombination hotspots.

The hippocampus is a brain structure known for its role in declarative memory- our ability to consciously recall facts and events. The hippocampus is a highly heterogeneous brain structure, and the small subregion CA2 has been shown to be necessary for the formation of social memories, the ability of an animal to recognize previously encountered conspecifics. Changes in excitatory/inhibitory balance have been observed in CA2 in humans with schizophrenia and in mouse models of schizophrenia, suggesting that these alterations may lead to some of the social dysfunction seen in schizophrenia. Although the hippocampal CA2 region has been implicated in social memory and neuropsychiatric disorders, little is known about how CA2 neural activity may encode social interactions and how this coding may be altered in disease. To see if and how CA2 codes for social interactions, I recorded extracellularly from CA2 pyramidal neurons as mice engage in a three-chamber social interaction task where the mice interact with the following task dimensions: space, novel objects, familiar social stimuli, novel social stimuli, and the passage of time. I found that whereas CA2 activity fails to provide a stable representation of space, unlike most other dorsal hippocampal subregions, it does code for contextual changes and for novel social stimuli. In Df(16)A+/- mice, which model the 22q11.2 microdeletion, a major schizophrenia risk factor, CA2 activity fails to encode context or social novelty, consistent with the deficit in social memory seen in these mice. In contrast, CA2 activity shows a surprising increase in spatial coding in Df(16)A+/- mice. These mice were previously shown to have a loss of inhibitory neurons within CA2, and a hyperpolarization of the CA2 pyramidal neuron resting potential. This hyperpolarization is likely due to upregulation of the outward rectifying TREK-1 K+ channel. I found that administration of a TREK-1 K+ channel antagonist rescued social memory and restored the normal CA2 coding properties in the mutants. These results demonstrate a crucial role for CA2 in the encoding of social stimuli and the expression of social memory, and suggest that dysfunction in CA2 may underlie deficits in social function seen in some forms of neuropsychiatric disease.

In this dissertation I study how different cognitive constraints affect individuals' belief formation process, and the consequences of these constraints on behavior. In the first chapter I present laboratory experiments designed to test whether subjects' inability to perform more rounds of iterated deletion of dominated strategies is due to cognitive limitations, or to higher order beliefs about the rationality of others. I propose three alternative explanations for why subjects might not be doing more iterations of dominance reasoning. First, they might have problems computing iterated best responses, even when doing so does not require higher order beliefs. Second, subjects might face limitations in their ability to generate higher order beliefs. Finally, subjects' behavior might not be limited by cognitive limitations, but rather justified by their beliefs about what others will play. I design two experiments in order to test these hypothesis. Findings from the first experiment suggest that most subjects' strategies (about 66%) are not the result of their inability to compute iterated best responses. I then run a second experiment, finding that about 70% of the subjects' behavior come from limitations in their ability to iterate best responses and generate higher order beliefs at the same time, while for the other 30% their strategies are a best response to higher order beliefs that others are not rational. In the second chapter I study whether a Sender in a Bayesian Persuasion setting (Kamenica and Gentzkow, 2011) can benefit from behavioral biases in the way Receivers update their beliefs, by choosing how to communicate information. I present three experiments in order to test this hypothesis, finding that Receivers tend to overestimate the probability of a state of the world after receiving signals that are more likely in that state. Because of this bias, Senders' gains from persuasion can be increased by ``muddling the water'' and making it hard for Receivers to find the correct posteriors. This contradicts the theoretical result that states that communicating using signal structures is equivalent to communicating which posteriors these structures induce. Through analysis of the data and robustness experiments, I am able to discard social preferences or low incentives as driving my results, leaving base-rate neglect as a more likely explanation. The final chapter studies whether sensory bottlenecks, as oppose to purely computational cognitive constraints, are important factors affecting subjects' inference in an experiment that mimics financial markets. We show that providing redundant visual and auditory cues about the liquidity of a stock significantly improves performance, corroborating previous findings in neuroscience of multi-sensory integration, which could have policy implications in economically relevant situation.

Preventing healthcare-associated infections (HAI) is a national priority. The Centers for Disease Control and Prevention estimates that one of every 25 hospitalized patients contract a HAI while receiving care. In 2009, the annual cost for HAIs in United States’ hospitals was estimated to be $40 billion, and there were 99,000 HAI-associated deaths. In nursing homes (NH), the situation is more dire; among the 4 million NH residents each year, there are 1-2.6 million serious infections and 1 out of every 3 NH residents is colonized with a multi-drug resistant organism. In addition to the frequent infections, over prescription of antibiotics in NH is significant, and frequently inappropriate. NH residents with HAIs are subjected to burdensome treatments and diagnostic procedures, leading to more complications in an already vulnerable population in which quality of life not life prolongation is often the treatment goal. Policy levers are actions designed to realize health objectives that can be taken by either public or private entities, and by individuals or groups. Health policy levers are deployed at all levels including federal, state, regional, and local levels. Vaccinations, such as polio, are one of the great success stories of how policy levers can prevent infections. However, undermined and eroded policy levers can have negative public health consequences, such as seen with the 2018-2019 rash of measles outbreaks. There is much work left to be done improving quality related to infections across all care settings. For this dissertation, I utilized the three-paper format and conducted studies examining the effectiveness of health policy levers used to improve healthcare quality and prevent infections across care settings. These studies were: 1) a systematic review of the published evidence on state mandatory reporting of HAI in hospitals; 2) an environmental scan cataloging state supported initiatives in NH infection prevention, and; 3) a quantitative analysis on the effect of new federal NH regulations on NH quality and patient outcomes. In the systematic review, I found that mandatory reporting was associated with reduced central line associate bloodstream infection rates. The environmental scan demonstrated that wide variation existed between states’ initiatives to support infection prevention in NH. In the quantitative analysis, I found that new federal regulations were significantly associated in improved NH quality in UTI rates and vaccination rates for influenza and pneumonia infections. Based on these results, clinical providers, administrators, policy makers and researchers can use health policy levers to reduce infections and improve quality.

Happiness, ritual, and sovereignty are artists’ persistent aspirations in the African- and Afro-Asian diasporas. “The Cinema of Social Dreamers” explores why the dreamscape is increasingly becoming the creative form for the expression of these social ambitions. This dissertation particularly spotlights the award-winning films and new media projects that exploit the dreamscape aesthetic in contemporary Caribbean and diasporic art. My analysis focuses on this tropical region, as well as its transnational impact in Canada, Mexico, France, the United Kingdom, and the United States. Central to this manuscript are the artists Mariette Monpierre, Michelle Mohabeer, and Minia Biabiany. I specifically engage their questions of happiness, spirituality, sexuality, and sovereignty in the wake of colonialism. The range of the narrative media these artists employ—from installation art and new media to sensational melodramas—also evidences the richness of the contemporary moment. While their award-winning works have flourished in niche film festivals and at fine art institutions, “The Cinema of Social Dreamers” is the first to present them as the subject of deep comparative analysis. By placing the Caribbean archipelago at the center of my work, I also highlight that the economy of art-making (and art history) remains a complex interdisciplinary, multilingual, and transnational project.

Accurate determination of the structure of nanomaterials is a key step towards understanding and controlling their properties. This is especially challenging for small nanoparticles, where traditional electron microscopy provides partial information about the morphology and internal atomic structure for a limited number of particles, and x-ray powder diffraction data is often broad and diffuse and not amenable to quantitative crystallographic analysis. In these cases a better approach is to use atomic pair distribution function (PDF) analysis of synchrotron x-ray total scattering data, in tandem with high-resolution imaging techniques. Even with these tools available, extracting detailed models of nanoparticle cores is notoriously difficult and time consuming. For many years, poor fits were considered to be a de facto limitation of nanoparticle studies using PDF methods, and semi-quantitative analyses were commonly employed. In this work, we aim to challenge this assumption. We started with a survey of 12 canonical metallic nanomaterials, both elemental and alloyed, prepared using different synthesis methods, with significantly different shapes and sizes as disparate as 2 nm wires and 40 nm particles, using PDF data collected at multiple synchrotron sources and beamlines. Widely applied shape-tuned attenuated crystal (AC) fcc models proved inadequate, yielding structured, coherent, and correlated fit residuals. However, equally simple discrete cluster models could account for the largest amplitude features in these difference signals. A hypothesis testing based approach to nanoparticle structure modeling systematically ruled out effects from crystallite size, composition, shape, and surface faceting as primary factors contributing to the AC misfit, and it was found that these previously ignored signals could be explained as originating from well defined domain structures in the nanoparticle cores. This analysis gave insight into how sensitive PDF analyses could be towards identifying the presence of interfaces inside ultrasmall nanoparticle cores using atomistic modeling, but still hinged on manual trial-and-error testing of clusters from different structural motifs. To address this challenge, we developed a structure screening methodology, called cluster-mining, wherein libraries of clusters from multiple structural motifs were built algorithmically and individually refined against experimental PDFs. This differs from traditional approaches for crystallographic analysis of nanoparticles where a single model containing many refinable parameters is used to fit peak profiles from a measured diffraction pattern. Instead, cluster-mining uses many structure models and highly constrained refinements to screen libraries of discrete clusters against experimental PDF data, with the aim of finding the most representative cluster structures for the ensemble average nanoparticle from any given synthesis. Finally, we wanted to identify other nanomaterial systems where this approach might prove useful, and demonstrated that the PDF was also capable of detecting seemingly subtle morphological variations in highly faceted titania photocatalyts. This opens a new avenue towards characterizing shape-controlled metal oxide nanomaterials with well-defined surface facets. To extend this work in the future, our goal is to develop new tools for building discrete nanoparticles algorithmically, integrate statistical approaches to make model selection more efficient, and ultimately, move towards an atomic scale understanding of nanoparticle structure that is comparable to bulk materials.

I apply a suite of seismic techniques to investigate iceberg calving at large glaciers around Greenland. Iceberg calving accounts for up to half of the Greenland Ice Sheet's annual mass loss, which makes understanding the physics of the calving process vital to gaining a clear picture of current behavior and future evolution of the Greenland Ice Sheet. However, the varied and complex modes of calving behavior at individual glaciers, paired with the challenges to data collection presented by an actively calving glacier, mean that much remains unknown about the dynamics of calving at marine-terminating glaciers. Seismic data offer a unique opportunity to study this active phenomenon, by allowing remote observation of calving events and quantification of the forces active during calving. Using seismic data collected during the most productive three years of buoyancy-driven calving on record, I estimate the forces active during iceberg calving at 13 glaciers around Greenland. My waveform-modeling results highlight the large number of buoyancy-driven calving events currently occurring at Jakobshavn Isbrae and other glaciers in west Greenland. I demonstrate that a glacier's grounded state exerts control on the production or cessation of rotational calving events and investigate the dynamics of calving at individual glaciers. I pair seismic results with terminus imagery to identify the location of individual calving events within calving sequences that occur over days to weeks at a single glacier terminus. By applying a new cross-correlation technique to seismic data collected within 100 km of three of Greenland's largest glaciers, I identify the occurrence of buoyancy-driven calving events with iceberg volumes up to two orders of magnitude smaller than previously observed. These small calving events frequently occur within ~30 minutes of a larger calving event. In between calving sequences, a glacier terminus changes little, suggesting that the majority of ice lost from marine-terminating glaciers occurs through these sequences. I estimate that these small events may contribute up to 30% more to dynamic mass loss than previously thought (up to 15 Gt/yr). I find no evidence of the cliff failure predicted by the marine-ice-cliff-instability hypothesis, in which catastrophic failure occurs when an ice cliff reaches a theoretical maximum-height limit, despite the three glaciers I investigate in detail having some of the tallest ice cliffs in the world. I use independent constraints on iceberg size from high-quality terminus imagery to present the first demonstration of an empirical relationship between glacial-earthquake magnitude and iceberg size. I investigate this relationship further by considering additional metrics of glacial-earthquake magnitude, and find advantages to using maximum force, rather than the more commonly employed mass-distance product Mcsf, as a measure of glacial-earthquake size. Through a detailed investigation into the character of the glacial-earthquake source, I identify key characteristics of the source function that generates the glacial-earthquake signal. I use experiments on both synthetic and observed waveforms to demonstrate that more-accurate estimates of glacial-earthquake size can be retrieved using source models constructed using a representation of the force history that is more sophisticated than that captured by the simple boxcar model. I confirm the presence of a correlation between iceberg volume and glacial-earthquake size, which moves us closer to having the ability to use remotely recorded seismic signals to quantify mass loss at Greenland glaciers. This work presents testable hypotheses for future model development.