71446 research outputs found
Sort by
Contesting Svalbard: Navigating Arctic Futures
No full textSvalbard is an archipelago built on an irreducible plurality of interests and Arctic design traditions. Norway has sovereignty over the island group. Contesting Svalbard combines a granular understanding of the spatial implications of multinational occupation in Svalbard with a critique of the Norwegian nationalism underlying the Svalbard project.
The Svalbard Treaty grants all 46 signatory states equal rights to conduct commercial and scientific research activities on the archipelago. This results in an intricate mix of interests and stakeholders and a unique foundation for design experimentation, collaboration, and speculation in an Arctic context. Norway is, however, tightening its grip on Svalbard, impacting the idea of Svalbard as an Arctic common imagined and designed by many nations and people groups.
Five distinct challenges in Svalbard’s built environment are identified as fertile ground to inject a range of alternative futures, catalyzing the archipelago’s multinational character. A participatory and scenario planning approach based on design research is central to such an endeavor. This study, therefore, deals with and speculates about a cross-cultural, fluid, and plural set of issues and actors in an increasingly contested Arctic common.
This study results in (i) adaptations to The Svalbard Treaty addressing climate change, the empowerment of minority groups, and the increasing diversity of interests in the region; (ii) design recommendations and scenarios foregrounding Thai and other Asian-Arctic interests in Svalbard’s built environment; (iii) a proposal for new material assemblies promoting the entanglement of multiple—existing and speculative—Arctic design traditions found in Svalbard; (iv) the introduction of a new transnational organization, The Central Arctic Ocean Design Agency, streamlining inclusive knowledge exchange across the Arctic and guiding alternative futures for Svalbard; and (v) a baseline condition where Norwegian dominance on Svalbard continues in the form of a new company town proposal.
This dissertation is geared toward an international design audience. It acts as a body of actionable knowledge to inform future development on Svalbard while curating and expanding the scope, practice, and literature on urbanism within Arctic contexts. This study also aims to supplement natural and social sciences on Arctic topics, challenge dominant literary histories, and unfold new spatial orders by transversing multiple nation-states, looking beyond the old polarities of hegemony.Advanced Studies Progra
Investigations of bacterial natural products in microbe-microbe interactions
No full textBacteria are prolific producers of natural products, diverse secondary metabolites that can play crucial roles in their survival, interactions, and environmental adaptation. While many natural products have been harnessed to treat human diseases, their ecological functions in natural environments are often overlooked and poorly understood. In complex microbial communities encompassing bacteria, fungi, and viruses, natural products shape microbial interactions and ecosystem dynamics, with potential implications for host homeostasis. An understanding of their functions and downstream impact may inform new strategies for manipulating microbial communities in medical, agricultural, and environmental applications. This dissertation documents our efforts to advance our understanding of the ecological roles of colibactin, a genotoxin produced by strains of Escherichia coli found in the human gut. It also reveals a newly discovered function for aryl polyenes, a highly abundant class of Gram-negative bacterial natural products. These investigations have revealed unprecedented roles for these compounds and their influence on the viruses that infect bacteria (bacteriophages), offering new perspectives on the chemical language that shapes microbial communities.Chemistry and Chemical Biolog
Sustenance: Ag Society's Grounds in 2059
No full textSustenance is the substance of distinct flavors, textures, colors, and nutrients that nourish living beings and allow them to thrive together. Yet, sustenance remains in the periphery of landscape architecture and on Ag Society’s grounds on the island of Noepe, Martha’s Vineyard. Appearance considerations have taken over the physical practices of sustenance.
Sustenance: Ag Society’s Grounds in 2059 proposes communal foraging to address the ongoing fragmentation of relationships between land, people, fauna, and flora. Forest forage expands the existing sustenance on site. Garden forage invites land-based practitioners from Wampanoag communities, landscaping companies, conservation organizations, and farming communities to care, design, and share their abundance. Milkweed forage communes with monarchs and humans.
The aspiration is to integrate sustenance as a “connective tissue.” Shaping space for communal foraging nourishes the connections among the glacial outwash sand, Wampanoag communities, water, seasonal communities, moths, plant communities, working residents and commuters, ground-nesting bees, and more.Department of Landscape Architectur
Integrating Spin Defects with Thin-Film Silicon Carbide Devices
No full textThin film silicon carbide (SiC) is a material used in commercial power electronics, and finding application in quantum information processing, microelectromechanical systems, photonics, and harsh environment sensors. Desirable in these applications is obtaining thin film-suspended device layers of undoped silicon carbide, which could be used as the basis of SiC-on-insulator (SiCOI) or for suspended photonics. It is an open challenge to obtain scalable thin films of single crystal silicon carbide, a challenge addressed in detail in this dissertation by implementing a dopant free photoelectrochemical (PEC) etching of SiC. In this dissertation we examine several incarnations of suspended SiC devices, and examine their potential for use in spin defect control, mechanical oscillators, and optical cavities.
In initial experiments, the photoluminescence and spin properties of ensembles of color centers in silicon carbide are enhanced by fabricating optically isolated slab waveguide structures using a doped PEC process and carefully controlling annealing and cooling conditions. We find that the photoluminescence signal of an ensemble of implanted defects is enhanced in slab waveguides by an order of magnitude over identically implanted bulk defects. The slab waveguide-enhanced photoluminescence of several defect species is used to study recombination and diffusion in the presence of thermal annealing with both rapid quench cooling and a longer return to ambient conditions. The confined mechanical geometry of a thin film is exploited to measure the spin-strain coupling of the negatively charged silicon monovacancy. The methods in this work can be used to exercise greater control on near-surface emitters in silicon carbide and better understand and control the effects of strain on spin measurements of silicon carbide based color centers. On the basis of these results we conclude that the properties of defects and devices are likely strongly degraded by the use of heavily doped epilayers.
Consequently, we reexamine in detail and then redesign the photoelectrochemical etching process used to suspend the devices to be compatible with a fully undoped device layer of SiC. PEC etching is a simple, rapid means of wet processing SiC, including the use of dopant selective etch stops that take advantage of mature SiC homoepitaxy. However, dopant selective photoelectrochemical etching typically relies on highly doped material, which poses challenges for device applications such as quantum defects and photonics that benefit from low doping to produce robust emitter properties and high optical transparency. In this work, we develop a selective photoelectrochemical etching process that relies not on high doping but on the electrical depletion of a fabricated diode structure, allowing the selective etching of an n-doped substrate wafer versus an undoped epitaxial (carrier density of 1(10)^{14}\unit{\cm}^{-3}) device layer. We characterize the photo-response and photoelectrochemical etching behavior of the diode under bias and use those insights to suspend large (100\unit{\um}\times100\unit{\um}) undoped membranes of SiC. We further characterize the compatibility of membranes with quantum emitters, performing comparative spin spectroscopy between undoped and highly doped membrane structures, finding the use of undoped material improves ensemble spin lifetime by . Furthermore, we examine these use of these films in the initial incarnations of photonic crystal cavities and mechanical "trampoline" type oscillators. This work enables the fabrication of high-purity suspended thin films suitable for scalable photonics, mechanics, and quantum technologies in SiC.
Next, we consider electrically driven mechanical oscillators fabricated using a front-side back-side dry etch, known as Lateral Overtone Bulk Acoustic Resonators (LOBARs) and the coupling of their dynamic strain to defect centers in the SiC. Here we report acoustic spin control of naturally occurring negatively charged silicon monovacancies in a lateral overtone bulk acoustic resonator that is based on 4H silicon carbide. We show that acoustic driving can be used at room temperature to induce coherent population oscillations. Spin acoustic resonance is shown to be useful as a frequency-tuneable probe of bulk acoustic wave resonances, highlighting the dynamical strain distribution inside a bulk acoustic wave resonator at ambient operating conditions. Our approach could be applied to the characterization of other high quality-factor micro-electro-mechanical systems and has the potential to be used in mechanically addressable quantum memory.
Finally, we consider an unconventional means of introducing defects into already suspended material through the process of energetic laser irradiation (referred to here as "laser-writing"). High-yield engineering and characterization of cavity-emitter coupling is an outstanding challenge in developing scalable quantum network nodes. Ex-situ defect formation systems prevent real-time analysis, and previous in-situ methods are limited to bulk substrates or require further processing to improve emitter properties. Here, we demonstrate direct laser-writing of cavity-integrated spin defects using a nanosecond-pulsed above-bandgap laser. Photonic crystal cavities in 4H-silicon carbide serve as a nanoscope monitoring silicon monovacancy defect formation within the approximately 200\unit{\nm}^3 cavity mode volume. We observe spin resonance, cavity-integrated photoluminescence, and excited-state lifetimes consistent with conventional defect formation methods, without need for post-irradiation thermal annealing. We further find an exponential reduction in excited-state lifetime at fluences approaching the cavity amorphization threshold and show single-shot annealing of intrinsic background defects at silicon monovacancy formation sites. This real-time in-situ method of localized defect formation, paired with cavity-integrated defect spins, is necessary towards engineering cavity-emitter coupling for quantum networking.
The proceeding work establishes a basis for the fabrication of integrated quantum systems using silicon carbide and the defects therein, from the incorporation of defects through laser writing, to the creating of nanofabricated geometries using PEC etching, to the control and read-out of their ground state spins using mechanical resonators. Though the experiments herein often investigate different devices, defects, and techniques, the underlying theme is same: improving the integration of spin defects in SiC with realistic devices that could lead to their use in quantum sensing and information processing.Engineering and Applied Sciences - Applied Physic
Sanctuary: A Counter-Project for the Sacramento-San Joaquin Delta
No full textThe California Department of Water Resources has invested trillions of dollars in creating a centralized water supply system that has historically made the agricultural economy and Southern California’s urbanization possible. However, this system that exports and conveys waters, through the State Water Project and the Central Valley Project, is precarious and riddled with seismic risk, flooding, and subsidence problems. Moreover, it has largely viewed the Delta region as a sacrifice zone, ecologically and socioeconomically.
Using the lens of fish, this thesis proposes a public subsistence fishing destination and restorative fish habitat that creates opportunities for local water access and stewardship, while also addressing the precarity and exclusion of local communities that plagues the current system of water conveyance.Department of Landscape Architectur
Trustworthy Machine Learning Through Interpretability and Fairness
No full textThe deployment of machine learning (ML) systems across diverse domains has led to groundbreaking advancements in vision and language tasks. However, ensuring that these systems are trustworthy—encompassing attributes such as interpretability, fairness, reliability, and alignment with human values—remains a significant challenge. This dissertation develops novel methodologies to enhance trustworthiness throughout the ML pipeline, addressing critical issues in data preparation, model training, model evaluation, and model deployment. To improve data preparation, this dissertation introduces concept-based auditing frameworks that systematically identify harmful biases and misaligned associations in large-scale and synthetic datasets. In the model training stage, two architectural innovations are proposed: channel embed- dings that improve interpretability in multiplexed biological data and architectural enhancements for super-resolution tasks that ensure semantic consistency by preserving high-frequency details. In the evaluation stage, traditional performance metrics are expanded with a texture-based evaluation framework that provides more human-understandable, context-sensitive insights. Lastly, in the deployment stage, synthetic counterfactual generation and fine-tuning techniques are introduced to mitigate biases in deployed models, enhancing fairness while preserving performance. These contributions address the trustworthiness of ML systems holistically, bridging the gap between low-level computational processes and high-level human understanding. This dissertation advances ML research by providing a comprehensive framework that improves transparency, reliability, and alignment with societal values across the entire machine learning pipeline.Engineering and Applied Sciences - Computer Scienc
We All Have Bright, Blundering Eyes
No full textIn the weeks leading up to an important photo shoot, Anna Pierce, a portrait photographer, is called home to help her parents. She discovers that her family has been keeping her father’s failing health a secret. Anna struggles to come to terms with her father’s mortality amidst what she perceives to be the smallness of her hometown. As she juggles the demands of her job with her father’s escalating periods of turmoil, another unexpected truth comes to light that shatters everything Anna thought she knew about her family. This is a story of flawed, but deep, familial love that must reconcile itself to the past or risk being broken apart forever.Extension Studie
Advancing Molecular and Functional Understanding of Cells with Artificial Intelligence
No full textRapid advancements in biotechnology are transforming our ability to measure biological systems across multiple modalities and scales. On the molecular level, spatially resolved single-cell transcriptomics enables comprehensive profiling of gene expression while preserving the spatial architecture of tissues. On the functional level, flexible brain-machine interfaces permit stable, long-term recordings of single-neuron activity throughout behavioral learning and disease progression. These innovations have increasingly shifted the life sciences toward a data-centric paradigm. However, traditional computational modeling approaches remain limited in their capacity to extract meaningful biological insights from heterogeneous, high-dimensional data, especially for decoding complex cell states and functions across space and time. To address this critical gap, this dissertation introduces a suite of computational methods that integrate artificial intelligence and machine learning (AI/ML) with cutting-edge biotechnologies. These methods are designed to interpret large-scale, multimodal biological data and feed insights back into experimental design for iterative discovery.
Chapter 2 presents ClusterMap, a spatially informed, unsupervised clustering framework for single-cell and tissue segmentation directly from in situ transcriptomic data. Building on this, Chapter 3 builds a comprehensive spatial atlas of the mouse central nervous system by integrating single-cell gene expression and spatial data at subcellular resolution. To generalize spatial analysis across datasets and technologies, Chapter 4 introduces FuseMap, a universal deep-learning framework that harmonizes multiple brain atlases into a common coordinate framework, enabling gene imputation, tissue region annotation, and cross-dataset integration. Expanding beyond transcriptomics, Chapter 5 introduces AutoSort, a real-time multimodal spike sorting algorithm for stable long-term neural recordings, and UnitedNet, a multi-task learning model that jointly performs cell-type identification, cross-modal prediction, and feature relevance discovery across diverse single-cell modalities.
In summary, this dissertation presents novel AI-powered frameworks that bridge molecular and functional modalities at the single-cell level. These approaches not only enhance our ability to decode the complex architecture and dynamics of biological systems but also provide a foundation for future integrative studies in development, disease, and therapeutic response.Engineering and Applied Sciences - Engineering Science
Watch Your Language: Detecting and Quantifying Political Bias In Large Language Models
No full texts large language model use begins to infiltrate academic and professional applica-
tions, it’s important to understand their biases and idiosyncracies as they could have
demonstrable effects on produced work that can reverberate throughout a field.
This paper takes the unique approach in measuring aggregate biases through com-
paring urtext to summarized text–a distinct technique that allows us to measure the
true effects in a natural setting. Our corpus of data comes from oral arguments from
Supreme Court cases, other miscellaneous texts associated with these cases and deci-
sions, and speeches from the Congressional Record. This data is useful as it contains
inherent proxies for political leaning. This data is also unique in how the political bias
is less explicit and instead resides in interpretation, allowing the study to probe at the
question at whether or not these languages models are conscious of their implicit po-
litical biases. From an initial set of results from applying naive techniques and existing
methodologies from political science literature, there were measurable differences be-
tween urtext and summarized text in regard to their leanings and confirm those behav-
iors through a second set of experimental techniques focused on more explicitly politi-
cal speech. From these results, the paper also presents a preemptive policy solution for
possible future harms presented by these models.Computer Scienc
Peeking Through the Iron Curtain: How Finnish Television Influenced Politics and Culture in Soviet Estonia
No full textThis paper examines the causal impact of accidental exposure to Finnish television on politi cal attitudes and voting behavior in Soviet Estonia. To isolate the effect of Western media on post-independence parliamentary election outcomes I exploit a unique natural experiment: differential access to Finnish television determined by geographic features. Combining novel data on broadcast signal strength with municipal-level voting outcomes in the pre- and post- Soviet periods, I adopt three complementary empirical methods: fixed-effects weighted least squares, a difference-in-differences event study, and a regression discontinuity design. The results reveal that exposure to Finnish television increased vote shares for parties that promoted democratic values, a market economy, fiscal conservatism, business incentives, welfare policies, and civil rights, and decreased support for parties endorsing marxist ideologies and the need for strong central authority. Mechanism analyses using archival records and survey data indicate that (i) Finnish television had a particularly strong impact on younger audiences, and (ii) the shift in voting behavior was driven primarily by Western entertainment content rather than explicitly political programming. This highlights the power of non-political media as a compelling vehicle for democratic soft power, capable of driving significant political change even in authoritarian regimes.Applied Mathematic