Short period body waves unveil deep Earth’s small-scale structure: from a subducted slab to the core
Contributors: Wu, Wenbo, Irving, Jessica C. E., Geosciences Department
... The current thermochemical state of the Earth’s interior is key to understand the evolution of the Earth. Seismic imaging can provide critical constraints on its thermochemical state. Although great progress has been made on large-scale seismic imaging, imaging small-scale structures is more difficult due to more complex wave propagation effects for short period waves. In this dissertation, I investigate several types of short period signals traveling in the deep Earth and use their properties to constrain the structure in Earth’s inner core, outer core and the subducted oceanic crust of the Pacific plate beneath NE Japan. Strong small-scale (a few km) volumetric heterogeneities in the inner core have been detected using short period (∼1 s) inner core scattering (ICS), termed PKiKP coda, in previous studies. However, most of these data sampled the inner core’s “eastern hemisphere”. I observed PKiKP and its coda waves sampling the “western hemisphere” and confirmed small-scale heterogeneities in the inner core’s “western hemisphere”. However, the ICS from “western hemisphere” is weaker than that from the “eastern hemisphere”. This hemispherical difference, or a regional variation, is also seen other properties of the inner core, such as anisotropy and average compressional wave velocity, Vp. Previous studies of body waves have imaged a low Vp layer at the top of outer core indicating a stratified layer. To better resolve this low Vp layer, I developed a novel approach using array data to iteratively isolate individual SmKS (m = 3, 4 and 5) signals and better measured SmKS-SKKS differential travel times. I successfully used this method to measure SmKS travel time delays. I also applied this iterative scheme on SPECFEM3D globe synthetic SmKS seismograms to investigate the effects of 3D mantle structure. The results indicate that 3D mantle structure effects are not negligible in our data and could bias the estimation of Vp in the uppermost outer core. After 3D mantle structure corrections, there are still substantial time delays for supporting a low Vp at the top of Earth’s outer core, relative to the PREM. Subducted oceanic crust plays an important role in material recycling (e.g. water) and the genesis of seismicity. Oceanic crust is usually thinner than 10 km and difficult to image. I observed seismic multi-pathing effects in the subduction zone below NE Japan. These multi-pathing effects are controlled by a seismic attenuation contrast between the back-arc mantle wedge and subducted crust. I used an oceanic crust model based on mineral-physics and conducted SPECFEM2D numerical simulations to investigate these multi-pathing effects. My results support a 9% Vp increase in the oceanic crust at a depth of 130-150 km due to the (lawsonite, talc)-eclogite transition. Here I demonstrated three examples of using short period body waves to image deep Earth’s small-scale structure. A large amount of short period data accumulated in the last decades is still awaiting seismological analysis. Deciphering these signals will tremendously improve our understanding of small-scale structure in the deep Earth.
Contributors: Phillips, Reuben, Agawu, V. Kofi, Burnham, Scott, Music Department
... This dissertation seeks to reframe the scholarly understanding of Brahms’s creativity in the 1850s and ‘60s through a consideration of the composer’s engagement with German literature. Drawing on archival research undertaken in Vienna, I argue that Brahms’s early aesthetic worldview was fundamentally shaped by his devotion to reading. The later chapters of the dissertation draw on key works of German Romantic literature to contextualize two of Brahms’s singular offerings in the fields of chamber music and song. Part 1 provides the first comprehensive investigation of an important source for evidence of Brahms’s early reading habits: his notebooks of literary quotations known – since their abridged publication in 1909 – as Des jungen Kreislers Schatzkästlein. Chapter 1 situates Brahms’s quotation collection in three contexts, considering biographical representations of Brahms as a reader, the role played by Robert Schumann in shaping Brahms’s literary enthusiasms, and the elevated status afforded to the activity of reading in German culture of the mid nineteenth century. Chapter 2 provides a thematic summary of the notebook entries, suggesting that for Brahms the process of copying out quotations served as a means of meditating on important ideas about the role of art in society, genius, originality, and artistic technique. An appendix provides a transcription of surviving source materials from copies preserved in the Wienbibliothek im Rathaus. In the second part of the dissertation I enlist some of Brahms’s beloved works of German Romantic literature in the examination of two compositions from the 1860s: the Trio for Piano, Violin, and Waldhorn, op. 40, and the Magelone Romanzen, op. 33. Following the lead of early critics, Chapter 3 considers the Horn Trio from the perspectives of affect and musical temporality in relation to the literary topos of the Romantic horn call. Chapter 4 offers a literary and music-analytical account of the Magelone Romanzen, homing in on Brahms’s formally innovative treatment of Tieck’s poetic texts. By exploring these works as imaginative musical responses to themes and motifs central to the literature of German Romanticism, this pair of close readings demonstrates some of the ways in which Brahms’s youthful reading fed his mature creativity.
Connectivity of the Posterior Cerebellum: Transsynaptic Viral Tracing with Light-Sheet Imaged Whole-Mouse Brains
Contributors: Pisano, Thomas John, Wang, Samuel S.-H., Molecular Biology Department
... The cerebellum is conserved across vertebrate evolution, representing a constant mammalian brain fraction. Classically, the cerebellum has been associated only with motor functions. However, the nonmotor role of the cerebellum has recently begun to attract greater attention; currently, its role in brain processing is poorly understood. Cerebellar disruption has consequences beyond motor coordination. Injuries to the posterior cerebellum produces a cognitive-affective syndrome characterized by nonmotor impairment in executive function and affect. The cerebellum receives substantial input from nonmotor cortical regions and projects back to the neocortex. Much evidence has come from neuroanatomical viral tracing studies in primates, suggesting polysynaptic loops join forebrain areas with the cerebellum. Enriched understanding of nonmotor cerebellar function can be achieved by identifying cerebellar polysynaptic connections to nonmotor neocortical areas. Anatomical studies of nonmotor cerebello-cortical loops are instructive of the cerebellum’s role in cognition and affect-function derived from structure. Transsynaptic tracing, histology, and subsequent analysis have challenges including low detection signal, tissue sectioning damage, and biases from manual quantification and anatomical assignment cells. Primary contributions of the thesis involve combining viral tracing with histological techniques for automated quantification of transsynaptic connectivity. I have optimized tissue clearing techniques for detection of virally-infected cells, allowing for volumetric imaging of whole-mouse brains with light-sheet microscopy. Using computational alignment software, I can automatedly and reproducibly register brain volumes to an atlas, removing error-prone manual structure identification. I have generated a local atlas with a complete cerebellum, which maintains translatability with the field standard that lacks the posterior cerebellum. This approach serves as a template solution anatomical commutability across research groups. Using neural networks, we have developed a three-dimensional cell detection pipeline capable of efficiently and accurately detecting polysynaptic connectivity in large brain volumes. Using this pipeline, I present findings showing the cerebellum densely projects to and can influence nonmotor brain regions with functions typically associated with autism spectrum disorder.
Contributors: McCready, Amelia Renee, Bassler, Bonnie L, Molecular Biology Department
... Quorum sensing is a cell-to-cell communication mechanism that bacteria use to orchestrate collective behaviors. Quorum sensing relies on the production, release, accumulation, and detection of extracellular signal molecules called autoinducers. The opportunistic pathogen Pseudomonas aeruginosa possesses multiple quorum-sensing systems, each composed of a receptor-autoinducer pair. Two of the P. aeruginosa quorum-sensing receptors, LasR and RhlR, are canonical LuxR-type receptors, meaning that they closely resemble the founding quorum-sensing receptor, as well as quorum-sensing receptors present in other species of Gram-negative bacteria. The cognate autoinducers for LuxR-type receptors are homoserine lactones. When bound to their ligands, LuxR-type receptors function as transcription factors that activate hundreds of genes underpinning collective behaviors. This work explores LasR and RhlR ligand binding preferences to understand how each of these receptors interacts with cognate and non-cognate ligands and how receptor-ligand interactions drive regulation of downstream quorum-sensing products. First, the work shows how LasR distinguishes between similar homoserine lactones as well as how LasR preferentially selects its own ligand from a mixture of related molecules. Second, the work reports RhlR ligand-independent mutants that display constitutive activity in vivo, providing insight into the enigmatic RhlR structure. Furthermore, the research demonstrates how the activities of RhlR ligand-independent mutants are kept in check with respect to regulation of quorum-sensing products. Finally, this thesis uses a RhlR ligand-independent mutant to reveal how RhlR works in conjunction with the PqsE thioesterase to regulate the production of the critical virulence factor pyocyanin.
Contributors: Petkas, Alex James, Wildberg, Christian, Classics Department
... This dissertation is a study of the Greek letter collection of Synesius of Cyrene (ca. 370 - 415 AD) as the key to his literary oeuvre; I argue that the epistles were a project of political philosophy. Synesius was a Neoplatonist philosopher, student of Hypatia of Alexandria, and eventually became the Metropolitan Bishop of Libya. His letters attest to a community of philosophical friends spread across Libya, Egypt, Syria, and Constantinople, a group which included both pagans and Christians. Synesius' letters drew on a philosophical epistolary tradition which can be meaningfully traced back to Plato and Isocrates in 4th century B.C. Athens. His epistles, like those of near contemporaries Gregory of Nazianzus and emperor Julian, participate in the public culture of the so-called Second Sophistic of the high Roman empire, a context still relevant in the late antique east. Contemporary Neoplatonic philosophers such as Julian, Themistius, Syrianus, and Eunapius would have seen political philosophy as an applied, or practical, activity, in which the deployment of rhetoric for the good of the state was central. In carrying out his political philosophy, Synesius tried to promote the honor, or value, of his own version of philosophy against competing alternatives, especially various forms of Christian asceticism. His letters construct for his community an alternative imaginary space built on classical topography, as an alternative to the late antique city. Synesius' learned classicism was driven by moral and philosophical imperatives attested in other writings of his, and was an earnest response to his unique late antique situation, which included Evagrius of Pontus and the Origenist controversy. Letters from his episcopacy show his attempt to reimagine contemporary realities in classical terms, as he points out continuities where others see change, and contradictions where others see harmony. His letters thus illuminate the values and preoccupations of a less known but important sector of late antique Hellenic society, in which Hypatia was an important player.
Contributors: Fraga, Sean, Sandweiss, Martha A, History Department
... American interest in Asian trade propelled westward expansion and shaped the Pacific Northwest. In the early nineteenth century, Americans saw the Pacific Coast’s few harbors as portals between the continental interior and the Pacific Ocean, motivating westward expansion under presidents from Thomas Jefferson (who dispatched Lewis and Clark) to James Polk. Access to Pacific harbors structured Polk’s 1846 Oregon Treaty, which divided the Northwest between the United States and Great Britain. In the 1850s and 1860s, Euro-American settlers used steam-powered vessels to police indigenous people and enforce the region’s marine border during a volatile period that included the Stevens treaties, the 1856 Battle of Seattle, the 1858 Fraser River gold rush, and the 1859 Pig War, which started a years-long military standoff between the United States and Britain for control of the San Juan Islands. At the same time, cross-border trade drove support for American annexation of British Columbia. Between 1880 and 1910, four transcontinental railroads, part of an emergent global steam-powered transportation network, built to Northwest harbors to access Pacific trade. (These included Northern Pacific Railroad, Great Northern Railway, and Canadian Pacific Railway.) Boosters celebrated new connections to Asia, promoting Puget Sound as the "gateway to the Orient," even as other white Americans violently opposed the presence of Asian people. Maritime trade powered growth for port cities like Seattle and Tacoma, but brought problems like congested waterfronts and unsafe watercraft, inspiring a local strand of Progressivism to manage marine spaces for public benefit. In the twentieth century, water sustained Seattle’s suburban growth, as developers leveraged local connections provided by the mosquito fleet to build housing—steamboat suburbs, including one named Suquamish—on nearby rural waterfront land. Scholars generally describe American westward expansion in terrestrial terms, as a series of land acquisitions. This dissertation demonstrates that Americans also understood it as a terraqueous process, involving both terrestrial and aquatic areas. A terraqueous perspective on American history reveals that terrestrial stories are frequently entangled with aquatic spaces, "ungrounding" familiar narratives. This approach recovers the role of maritime workers in American territorial acquisition and settlement. It emphasizes the use of technology in border-making, demonstrating how Anglo-Americans used steamboats to counter indigenous maritime societies. It stresses the continuity between nineteenth-century American continental expansion and twentieth-century U.S. Pacific imperialism. And it models terraqueous possibilities for historical geography, showing how local maritime connections sustained urban and suburban growth. By revealing the terraqueous dimensions of American history, this research expands and challenges our understandings of American national incorporation, borders and borderlands, American engagement with the Pacific World, and urban and suburban development. American history looks different from the water’s edge.
Rethinking the Formal Domain: Deep Scientization of Design and Architecture-Engineering Hybrid, 1956-2006
Contributors: Araguez, Jose, Lavin, Sylvia, Architecture Department
... This dissertation identifies the emergence of a sublineage in the tradition of the architecture-engineering hybrid between the mid-1950s and the mid-2000s through an examination of the work of Vittorio Giorgini (1926–2010), Michaël Burt (b. 1937), and Cecil Balmond (b. 1943). These three figures operated at the margins of the architecture discipline, but none was an architect-engineer in any customary sense. Rather, it is the ensemble of their production that, embodying a three-dimensionality characteristic of the nature, purview, and scale of architecture—if strongly driven by science and by aspects traditionally associated with structural engineering—I interpret as constituting the said sublineage. The discussion of Giorgini’s, Burt’s, and Balmond’s bodies of work is here framed in relation to both the general and the particular conditions of possibility enabling their appearance: the general conditions being an overarching paradigm triggered by an acute scientization of design that unfolded across the West over the course of the second half of the twentieth century; the particular conditions—wired into the general—being the specific academic, professional, and discursive contexts in which each design thinking originated and evolved. I illustrate the degree to which each body of work, while determined by these two levels of contextual influence, was idiosyncratic with respect to both, and show the importance of their differentiating traits. For I argue and attempt to demonstrate that the architectural thinking embedded in the idiosyncratic character of the oeuvre of Giorgini, Burt, and Balmond gives rise to a realm of design that is a distinctly appropriate medium through which to craft a new conceptualization of form in architecture. In pursuing this argument and attendant conceptualization, I seek to rethink the bounds of the formal domain in architectural thinking. In contrast to formal epistemologies revolving around external envelope, volumetric outline, or “mass,” this study is grounded in the notion of spatial organization and related terms such as configuration, arrangement, and disposition. The former sphere of signification is made to correspond to “shape” and the latter to form proper.
Contributors: Liu, Changchang, Mittal, Prateek, Electrical Engineering Department
... Nowadays, more and more data, such as social network data, mobility data, business data, medical data, are shared or made public to enable real world applications. Such data is likely to contain sensitive information and thus needs to be obfuscated prior to release, to protect privacy. However, existing statistical data privacy mechanisms in the security community have several weaknesses: 1) they are limited in protecting sensitive information in the static scenario, and can not be generally applied to accommodate temporal dynamics. With the increasing development of data science, a large amount of sensitive data such as personal social relationships are becoming public, making the privacy concerns of a time series of data more and more challenging; 2) these privacy mechanisms do not explicitly capture correlations, leaving open the possibility of inference attacks. In many real world scenarios, the data tuple dependence/ correlation occurs naturally in datasets due to social, behavioral and genetic interactions between users; 3) there are very few practical guidelines on how to apply existing statistical privacy notions in practice, and a key challenge is how to set an appropriate value for the privacy parameters. In this thesis, we aim to overcome these weaknesses to provide privacy guarantees for protecting dynamic data structures, dependent (correlated) data structures. We also aim to discover useful and interpretable guidelines for selecting proper values of parameters in the state-of-the-art privacy-preserving frameworks. Furthermore, we investigate how an auxiliary information -- in the form of prior distribution of the database and correlation across records and time -- can influence the proper choice of the privacy parameters. Specifically, we 1) first propose the design of a privacy-preserving system called LinkMirage, that mediates access to dynamic social relationships in social networks, while effectively supporting social graph-based data analytics; 2) explicitly incorporate structural properties of data into current differential privacy metrics and mechanisms, to enable privacy-preserving data analytics for dependent/correlated data; and 3) finally provide a quantitative analysis of how hypothesis testing can guide the choice of the privacy parameters in an interpretable manner for differential privacy and other statistical privacy frameworks. Overall, our work aims to place the field of statistical data privacy on a firm analytic foundation that is coupled with the design of practical systems.
Contributors: Kustov, Alexander, Pop-Eleches, Grigore, Politics Department
... Widespread opposition to increasing immigration among educated and racially egalitarian voters is hard to explain using existing frameworks that attribute these sentiments to self-interest or prejudice. I address this puzzle by developing a theory of parochial altruism, which argues that voters often face an altruist's dilemma: they are willing to help others even at a personal cost, but they want to help their fellow citizens first. Thus, most altruistic voters who are partial toward their compatriots are expected to oppose globally beneficial policies that forgo their national interest. As a result, independent of their other concerns, voters tend to favor harsh immigration restrictions that they perceive as necessary to secure the well-being of compatriots. To test my theory against alternative explanations, I build on existing cross-national surveys and conduct an original population-based study with incentivized economic games and choice experiments in the UK and the US. First, using a novel measure of elicited preferences, I find that most altruists who choose to donate to domestic as opposed to global charities are as anti-immigration as those who choose not to donate at all. Second, using a pre-registered conjoint experiment of policy choice, I demonstrate that, despite ethnic biases, most voters can support increasing immigration from non-European countries if they believe it benefits themselves and their compatriots. Third, I replicate the analysis on environmental preferences and electoral behavior, indicating that the dynamic of parochial altruism generalizes across contexts. That is, at least in major high-income democracies with strong national institutions, voters decide based on what they think is good for themselves and their compatriots but pay little regard to global interests. Given the apparent failure of efforts to change negative perceptions of immigration, the results also suggest that a more effective government strategy is to consider new policy solutions that explicitly and straightforwardly benefit average citizens along with potential migrants.
Contributors: Hulme Kozey, Emily Luise, Wildberg, Christian, Classics Department
... “Good God! You never shut up about cobblers and fullers and cooks and doctors!” So Callicles charges Plato's Socrates with an excessive fascination with the τέχναι in the Gorgias (491a). Callicles certainly has a point: Plato refers to τέχνη (“art,” “craft,” “profession,” “expertise”) hundreds of times in the dialogues, while also portraying Socrates as a former δημιουργός (“craftsman,” “professional”) himself (Alc. 1.121a; Euthphr. 11c). In my dissertation, I examine the philosophical importance of τέχνη in Plato. The first part discusses the idea of τέχνη in the wider Greek world of the fifth and fourth centuries. Chapter one shows how Plato connects Socrates with the god of craft, Hephaistos, and how this is related to the Athenian setting of the dialogues. The second chapter uses literary, art historical, and epigraphic sources to identify four major features of a τέχνη: (I) connection with low social status; (II) teachability; (III) specialization; (IV) rationality. The second part of the dissertation turns to Plato proper. The third chapter examines the important question of how Plato’s terms for crafts, knowledge, learning, and professions are structured. Contrary to previous work that has asserted the equivalence of τέχνη and ἐπιστήμη, I argue that ἐπιστήμη picks up on the teachable, intellectual component of τέχνη. Against a common misconception, I argue that the opposite of τέχνη for Plato is not ἐμπειρία (“experience,” “practice”) but πάρεργον (“hobby”) and that this contrast, and the one made by the terms for the individuals who pursue each of these (δημιουργός/ἰδιώτης, “professional”/ “amateur”), is central to Plato’s conception of what makes something a true τέχνη. For Plato, mere book knowledge will not be enough: extensive practice or experience is, in fact, an absolute requirement for true mastery of a given field. The fourth and fifth chapters then turn to this theme in two related contexts. First, I assess how Plato portrays the sophists as practitioners of pseudo-τέχναι; and then, in the final chapter, I turn to the Republic, where philosophy itself is construed as a τέχνη.