VictorJuiz/thesis huggingface dataset:
Computation, mechanisms, and optimal coding in retinal adaptation [electronic resource]
Keywords: Electrical Engineering.

Sensory systems face the problem of encoding sensory signals that vary greatly, exceeding the operating range of individual neurons. As a consequence, neural systems dynamically adapt to the current sensory environment by changing their response properties. While this adaptive coding and its underlying mechanisms have been studied over decades, a lack of quantitative, biophysical models limits our understanding both of the mechanisms of adaptation and the principles by which the nervous system has been optimized through evolution. Synaptic transmission and spiking are two key mechanisms thought to contribute to adaptation in the retina and elsewhere in the brain. To understand how the computation of contrast adaptation arises, we developed an accurate dynamical, multi-stage model that included bipolar cell synaptic transmission and ganglion cell spiking. Using this model, we show that, paradoxically, spiking alone is anti-adaptive, but that synapses and spiking act synergistically to generate adaptation. We further analyzed the parameters of the model to understand how the retina balances the conflicting requirements of information transmission and energy conservation in a rapidly changing environment. We show that synergistic adaptation from synapses and spiking creates an optimal balance of information transmission and energy eciency in a dynamically changing environment. Our findings reveal synapses as the essential source of adaptation, with spiking enhancing that adaptation, and the two mechanisms together acting to maximize information transmission while conserving energy.
Computational limits in statistical estimation [electronic resource] : hidden clique and related problems
Keywords: Electrical Engineering.

Characterizing computational costs of statistical estimation and inference is a fundamental challenge. In many modern applications a confluence of both large-scale and high-resolution data has highlighted the computational challenges in extracting information and performing inference. For a number of reasons, the hidden clique problem from theoretical computer science has emerged as a prototypical example of the impact computational considerations can have on statistical estimation problems. In particular, the computational phenomena observed in the hidden clique problem are intimately related to analogous phenomena in other problems like sparse principal components analysis and learning communities in graphs. In this thesis, we study algorithm-based computational limits for the hidden clique problem and related problems. We use the popular approaches of the belief propagation heuristic, and convex programming relaxations for two aims: 1. We propose new algorithms that provably improve over the prior state-of-the-art methods for the hidden clique problem and sparse principal components analysis (PCA). 2. We provide hardness evidence for the hidden clique problem based on local algorithms, which generalize the belief propagation heuristic, and the powerful Sum-of-Squares hierarchy of convex programming relaxations.
Conceptual complexity and the evolution of the lexicon [electronic resource]
Keywords: Psychology.

Natural languages are filled with regularities. Where do these regularities come from? A parsimonious explanation is that these regularities emerge as a consequence of pressures within the broader context in which language is used: Communication among many cognitive systems. In this dissertation, I consider one particular regularity as a case study in how the dynamics of language use might shape language structure. Specifically, I focus on a bias in natural language to map long words on to conceptually complex meanings and short words on to conceptually simple meanings, or a complexity bias. Across a series of experimental and corpus studies, I explore whether languages and their speakers have a complexity bias, what conceptual complexity is, and what pressures might have lead to this bias over the course of language evolution. In the final chapter, I consider a broader range of linguistic phenomena and examine how aspects of language use might influence these structures.
Conflict and the Cross-Border Pipeline: Revisiting the "Commercial Peace"
Keywords: Center for International Security and Cooperation
pipelines
energy transit
cross-border
conflict
economic cooperation
Thesis

Cross-border pipelines are pipelines that cross at least one international boundary in order to transport natural gas or crude oil from one state to another. States and multinational enterprises are planning and building new cross-border pipelines to prepare for rising long-term energy demand, to facilitate oil and natural gas production in reserves located in landlocked countries, and to integrate regional energy markets. To build and operate a cross-border pipeline, states and firms must agree upon a breadth of terms, including ownership, operation, financing, right-of-way, contracted volumes, arbitration processes, and transit fees. Therefore, cross-border pipeline projects involve significant interaction among the participating states.
This thesis seeks to determine whether the interaction that enables cross-border pipelines to exist and operate increases or decreases conflict among the participating states. This thesis uses brief case studies to demonstrate that two opposite trends from existing literature may explain the effect of cross-border pipelines on interstate conflict. First, cross-border pipelines introduce additional economic interdependence between states, which empirical studies have already shown to decrease interstate conflict. Second, cross-border pipelines exhibit high asset specificity and are thus vulnerable to the hold-up problem, which increases interstate conflict. Converting a novel and comprehensive database of cross-border oil and natural gas pipelines to a dyad-year dataset, this thesis shows through empirical analysis that cross-border pipelines have no robust effect on the incidence of interstate conflict from 1946 to 1992.
Conformational transitions within an RNA enzyme [electronic resource]
Keywords: Biochemistry.

Biological catalysis hinges on the precise structural integrity of an active site that binds and transforms its substrates and meeting this requirement presents a unique challenge for RNA enzymes (ribozymes). Functional RNAs, including ribozymes, fold into their active conformations within rugged energy landscapes that often contain misfolded conformers and must undergo structural rearrangements to assume functional structures. Here I describe a series of projects that uncover conformational transitions within the active site of the group I ribozyme. Most generally, the results described in this thesis underscore RNA's tendency to form alternative structures, even within an RNA active site, and highlight the important of RNA conformational changes in allowing RNA to navigate a rugged conformational landscape. Despite the apparent difficulties that RNA faces in specifying a unique structure that would be optimal for catalysis, RNA enzymes have persisted to the modern day, and several of them, including the spliceosome and ribosome, coordinate complex multistep processes. Perhaps RNA's folding "problem" has been harnessed by Nature to evolve dynamic ribonucleoproteins such as the ribosome and spliceosome, which undergo local and global conformational changes during their functional cycles.
Conjuring cane [electronic resource] : the art of William Berryman and Caribbean sugar plantations
Keywords: Art and Art History.

This dissertation examines the depiction of sugar plantations in the colonial Caribbean, with a specific focus on Jamaica during the late eighteenth and early nineteenth centuries. Over the course of the eighteenth and early nineteenth century, there were few better examples of modern industrial labor systems than those found on Caribbean slave labor plantations, specifically those that produced sugar. These plantations were the nexus of the slave, sugar and rum trades. Though protected by mercantilist policies, these trade networks, and their arbiters, incredibly wealthy merchants based in the metropole, were capitalist at their core. The very functioning of the sugar plantation, with its state-of-the-art technology, and coordination of an enormous, highly disciplined labor force in the field with a highly skilled labor force the sugar mill under a rigorous, time-sensitive, and detailed schedule, was the epitome of modern labor. In addition to its economic and industrial impacts, the plantation was a site where new cultures were created through the process of what has at times been called creolization, hybridization, or cultural syncretism. Although crucial to modernity, the history of sugar plantations has often been overlooked in its histories in lieu of events like the Industrial Revolution or French Revolution. In this dissertation, I argue that the images produced and widely circulated of West Indian plantations, usually in the Picturesque style, created an impression of the plantation as a pastoral site, which, like the pastoral and Georgic images of rural British estates, not only placed these sites in a distant past, but also extracted them from their modern reality. The theories behind the Picturesque found their roots in the idea of the omniscient eye produced by property surveys, one of the first visual strategies aimed at representing land as privately owned capital. Thus, the Picturesque reinforced and naturalized European ownership and control over plantations at a time when, in many cases, that ownership was in peril. Countering this narrative is the work of artist William Berryman. Although his work has remained relatively unknown, his paintings and drawings of Jamaica in the early nineteenth century present a view of the inner workings of plantation society. This dissertation is the first extensive study of his archive, which contains approximately three hundred images from his eight year sojourn in Jamaica.
Connecting the Drops: The Negotiation of the Indus Water Treaty
Keywords:  Program in International Relations
Indus Water Treaty
Thesis

In a world burdened by burgeoning populations and faced with declining water resources, water is likely to trigger conflict. Since the partition of British India in 1947 and the creation of the modern states of India and Pakistan, the two South Asian countries have been involved in four wars (one undeclared), as well as many border skirmishes and military stand-offs. Yet despite being strong adversaries, India and Pakistan have had a comprehensive water treaty, the Indus Water Treaty, active for over 50 years. This thesis explores the complex, drawn-out negotiation of the treaty, from its beginnings in 1950 to its eventual creation in 1960. Furthermore, this thesis looks into the significance of the final agreement, and its implications for India and Pakistan’s overall relationship.
Considered opinions and better citizens [electronic resource] : public spiritedness, collective decisions, and issues of measurement
Keywords: Communication.

This dissertation explores the efforts to promote considered opinions and better citizens. The first chapter examines the relationship between deliberation and public spiritedness with scientific samples of the public who participated in seven Deliberative Polls on utility choices, and attempts to answer: a) do people become more public spirited after deliberation in the sense that they are willing to support the provision of public goods; and b) do they do so for identifiable reasons that are about the state of the community and not just the state of their own pocketbook? The second chapter of this dissertation attempts to explain the individual-level preference changes that underpin the aggregate phenomenon of deliberation-induced single-peakedness, which precludes majority cycles -- what individuals come to adopt single-peaked preferences, and more importantly, what underlying mechanisms cause the individuals to move closer to single-peakedness after deliberation? The final chapter of this dissertation examines four types of questions in six national or regional telephone surveys, and attempts to answer whether offering or omitting the middle alternative is good or bad in term of improving measurement validity and promoting more considered opinions.
Constraints on a 2D CFT Dual to Weakly Curved AdS Gravity
Keywords:  Department of Physics
conformal field theory
AdS/CFT correspondence
elliptic genus
modular invariance
pure supergravity
Thesis

An extremal CFT is a CFT whose spectrum matches that of pure gravity through the AdS/CFT correspondence. We examine the constraints imposed on the elliptic genus of an N = 2 extremal CFT for half odd integer values of 'm'. The integer case of 'm' has been previously studied. 'm' is a measure of the degrees of freedom of the theory, and it is half integrally quantized. We found that our CFT model with minimum content (i.e. only the vacuum module) did not satisfy the appropriate form requirements for an extremal polar polynomial. Thus, we conclude that we must add a minimal number of particle states to the bulk such that a ‘near extremal’ dual CFT exists.
Constraints on subglacial conditions from mechanical models of ice stream processes [electronic resource]
Keywords: Geophysics.

Motivated by the hazard associated with Antarctica's contribution to sea level rise, we examine localized regions of fast flowing ice called ice streams. We explore several recent observations from the Antarctic Ice Sheet with the goal of constraining subglacial conditions and improving our mechanical understanding of these systems. Our strategy generally consists of comparing the predictions of simplified mechanical models with geophysical data. We first examine seismic signals arising from the resonant vibrations of water-filled subglacial and englacial fractures, as well as fractures in other geological systems. We then shift attention to the Whillans Ice Plain (WIP) sector of the West Antarctica Ice Sheet (WAIS). The WIP experiences tidally-modulated, twice daily slip events. These slip events bear a striking similarity to subduction zone slow slip events. Slip events are accompanied by seismic tremor, which we additionally use to constrain subglacial conditions. We use the occurrence of ice stream slow slip events and tremor as an opportunity to validate rate- and-state friction as a glacier sliding law. For this reason, this thesis constitutes a step towards a more detailed description of the strength of the ice-bed interface.
Consumers, interrupted [electronic resource] : the effect of interruptions on persuasion and decision making
Keywords: Business.

Individuals experience a greater frequency of interruptions than ever before. In the current research, I find that interruptions provide opportunities for subjective cognitive experiences (e.g., curiosity, need for closure) to enter consumers' thought processes and shape their attitudes and decisions about products not only within the interrupted domain (Chapter 1) but also outside of it (Chapter 2). Chapter 1 reveals that interruptions that temporarily disrupt a persuasive message can increase consumers' processing of that message. As a result, consumers can be more persuaded by interrupted messages than they would be by the exact same messages delivered uninterrupted. In documenting this effect, the current research departs from past research illuminating the negative effects of interruptions, and delineates the mechanism through which and conditions under which momentary interruptions can promote persuasion. When consumers are prevented from returning to the interrupted information, Chapter 2 reveals that their unsatisfied desire to view the interrupted information manifests as a need for closure that reduces their processing of unrelated content. Together, this research illuminates the powerful impact that interruptions can have on consumer persuasion and decision-making.
Contribution of halides to photochemical reactions in estuaries and coastal waters [electronic resource]
Keywords: Civil and Environmental Engineering.

Photochemical reactions may serve to mediate natural processes and contaminant degradation in estuaries and oceans. While research into aquatic photochemistry has focused on freshwater-relevant pathways, the impact of high halide concentrations in saline waters—the primary characteristic distinguishing seawater from freshwater—on photochemical processes has received little attention. This dissertation characterizes how halides in seawater alter indirect photochemical reactions by (i) enabling the production of seawater-specific reactive intermediates such as halogen radicals and (ii) by impacting photoproduced reactive intermediates common between fresh and saline waters (e.g. excited triplet state dissolved organic matter, hydroxyl radical). This dissertation also discusses the implications of these altered photochemical processes for biogeochemical processes (e.g. the sulfur cycle) and contaminant degradation (e.g. algal toxins) in coastal and estuarine waters.
A contribution to improve facies object modeling of meandering rivers depositional systems [electronic resource]
Keywords: Energy Resources Engineering.

This work focuses on improving meandering river architecture in object-based modeling. Object-based modeling is used through the industry to replicate several depositional environments using defined geometries that intend to mimic reality. Meandering river environments, due to their specific and relatively well defined geobodies, are amongst the most represented by object modeling algorithms. Modeling of these systems is mostly controlled by the amount and distribution of its different constituent structures. Channel and levees facies are the main landforms characterized in the literature. These structures are represented by several commercial software often in an over simplistic geometrical form. Furthermore, other bodies pertaining to the meandering river architecture, such as point bars and splays are also not described properly or sometimes not even taken into account at all for modeling purposes. In this thesis, we propose an improved portrayal of meandering rivers not only with the inclusion of these additional landforms (point bars and splays) but by properly investigating and delineating its geometrical configurations and its inter-relation amongst these different arrangements. Application of the above proposed methodology is demonstrated through guided workflows.
Controls on along-strike variations in stratigraphy and provenance of a successor foreland basin system, Jurassic-cretaceous evolution of the southern Patagonian Andes and the Magallanes-Austral Basin [electronic resource]
Keywords: Geological and Environmental Sciences.

Sedimentary basins that develop adjacent to convergent plate margins are intrinsically linked to an array of tectonic processes, including those associated with subduction dynamics, crustal shortening, exhumation and topographic uplift, and lithospheric flexure. In turn, each of these processes help to govern the timing and nature in which sediment is transported from mountain belts to ocean basins. Thus, the stratigraphic fill of sedimentary basins is often the best available record for understanding the integrated evolution of convergent plate margins over geologic time scales. However, deciphering that record can be challenging in basin systems with complex histories that include multiple tectonic regimes, tectonic overprinting, and/or incomplete preservation of stratigraphy. This dissertation examines the influences that tectonic inheritance and predecessor basin history can have on the evolution of successor foreland basin systems. While previous workers have demonstrated the temporal influence of tectonic inheritance, this work assesses the spatial relationships by considering along-strike (orogen-parallel) variations in the timing of tectonic events (rifting, collision, basin initiation), stratigraphy and distribution of facies, and source area exhumation and sediment routing. The following four chapters explore the Jurassic--Cretaceous tectonic evolution of southern Patagonia, which consists of a two-part history that begins with the development of a predecessor backarc rift basin (the Rocas Verdes Basin) and is followed by a successor retroarc foreland basin system (the Magallanes--Austral Basin). Chapter 1 investigates the geochronology of rifting in the predecessor Rocas Verdes Basin from the northern (Austral) basin sector to assess the basin-scale, along-strike variability in relative timing and duration of Jurassic--Early Cretaceous rifting. Chapter 2 examines the distribution of deep-water facies and the relative timing of deposition that represents the transition to, and development of, foreland basin sedimentation in the Magallanes--Austral Basin. Chapter 3 explores the role of longitudinal vs. transverse sediment supply during the early evolution of the Magallanes--Austral foreland basin system. Finally, chapter 4 examines along-strike variations in the provenance, timing of deposition, and distribution of facies within a deep-water canyon channel system represented by the Upper Cretaceous (Turonian--Santonian) Cerro Toro Formation.
Convergence rates of a class of multivariate density estimators based on adaptive partitioning [electronic resource]
Keywords: Statistics.

Density estimation is a fundamental problem in statistics. It is a building block for other statistical methods, such as classification, nonparametric testing, and data compression. In this dissertation, I focus on a non-parametric approach to multivarite density estimation, and study the asymptotic behavior of this approach under both frequentist and Bayesian settings. The estimated density function is obtained based on consideration of a sequence of approximating spaces to the space of densities. The approximating spaces consist of piecewise constant density functions supported by binary partitions with increasing complexity. The partition is learned by maximizing either the likelihood of the corresponding histogram on that partition, or the marginal posterior distribution of the partition under a suitable prior. We analyze the convergence rate of the maximum likelihood estimator and the posterior concentration rate of the Bayesian estimator, and conclude that for a relatively rich class of density functions the rate does not directly depend on the dimension. Another result has significant practical implications: We show that the Bayesian method can adapt to the unknown complexity of the density function, thus achieving an optimal convergence rate without any prior information. We also apply this method to several specific problems, including spatial adaptation, estimation of functions of bounded variation, and variable selection.