VictorJuiz/thesis huggingface dataset:
Theories of large-scale neural recordings [electronic resource]
Keywords: Bioengineering.

Rapid technology developments in neuroscience are enabling us to record from an ever increasing number of neurons from the brain. However, with the deluge of experimental data, our ability to extract simple yet fundamental understandings of the neural mechanisms underlying behavior and cognition is hampered by a lack of theoretically principled data analytics procedures. In the present work, we outline a set of theoretical frameworks that begins to address this challenge. First, we focus on the analysis of trial-averaged data obtained over experimental repetitions of tightly controlled behaviors. We start by developing a theory of neural dimensionality, which explains the prevalence of low-dimensional dynamic portraits observed in system neuroscience. We then connect the experimental act of recording a random subset of neurons to the mathematical theories of random projection, and illustrate how we might understand anything about the brain given the infinitesimal fractional of behaviorally relevant neurons observed. The second part of the thesis addresses the analyses of single-trial neural data collected during potentially more complex or naturalistic behaviors that may not be repeatable. We explore the effects of trial-to-trial variability and neuronal noise in the context of several analytically tractable generative data models covering linear and nonlinear stimulus-response mappings as well as static and dynamic latent states. We derive exhaustively the functional dependencies of commonly applied analytics procedures' performances on the number of recorded neurons, the number of trials and other model specific parameters. For each of the theoretical puzzles addressed in this thesis, we formulate the question with mathematical precision, derive quantitative predictions testable against simulations and/or neural data, and provide guidelines for the interpretation of past results as well as the design of future experiments.
Theory and measurements of emittance preservation in plasma wakefield acceleration [electronic resource]
Keywords: Physics.

Plasma wakefield acceleration (PWFA) is a revolutionary approach to accelerating charged particles. In this dissertation, we present conditions for circular symmetry in the plasma wake. We present analysis of beam parameter and emittance matching, which predicts these values reach an equilibrium. We present and simulate a model for ion motion, and lay the foundation for simulations revealing emittance growth due to ion motion. By connecting a simple ion motion model and emittance theory, we calculate the emittance growth due to marginal ion motion to be minimal. We also present a proof-of-concept of an emittance measurement of PWFA beams.
Theory and simulation of dynamics in heterogeneous environments [electronic resource]
Keywords: Chemistry.

This thesis develops theoretical methods and simulation approaches to elucidate the dynamics of quantum mechanical processes in heterogeneous condensed phase systems. In the first part of the thesis, we consider non-equilibrium relaxation dynamics. These dynamics play a key role in many problems in chemistry, from exciton transfer in photosynthetic light harvesting to electron transfer in photocatalysis. We use the generalized quantum master equation (GQME) formalism in conjunction with quantum-classical methods to treat nonequilibrium relaxation for systems containing many quantum states, as well as fully atomistic systems. In these systems, we show that the GQME approach is highly accurate while also being more efficient than the same quantum-classical method used directly, sometimes by as much as three orders of magnitude. We present an importance sampling algorithm which efficiently generates the memory kernel of the GQME for systems with many quantum states. We then consider a series of cases where chemically tailoring a heterogeneous environment allows one to control reactivity and dynamics. In particular, we show that simulation can be used to elucidate the role of the environment in driving vibrational relaxation in functionalized self-assembled monolayers on gold. We find that vibrational dynamics measured in experiments on self-assembled monolayers arise from a variety of molecular motions including conformational rearrangement of gauche defects in the monolayer. We also show theoretically how the regioselectivity of a catalyst can be controlled by changing the solvent to enforce ion pairing. We find that mutual polarization of the ion pair and the solvent is a key source of the stabilization of ion-paired transition states that gives rise to selectivity that is observed in experiments. Overall, the theoretical methods and simulations presented allow us to accurately capture and elucidate the dynamics in a variety of heterogeneous condensed phase systems.
Thermomechanical degradation and failure mechanisms in thin film technologies [electronic resource]
Keywords: Materials Science and Engineering.

From photovoltaics to MEMS, modern technological advancement has increasingly been achieved via complex and multilayered thin film technologies. While thin film applications of materials enable high performance, they also introduce heterogeneities and interfaces which potentially lead to degradation and failure. In this work, I explore the mechanical and fracture properties of a diverse range of inorganic thin film materials, focusing in particular on brittle materials. Fragility of specimens presents an interesting challenge, as it precludes the use of more traditional testing methods, leading to development of new testing metrologies. Multijunction photovoltaics present one such challenge, possessing many internal interfaces of interest which have previously been uncharacterized due to substrate fragility. Photovoltaics need to maintain operational lifetimes in excess of 25 years in order to be economically competitive, and are subjected to a variety of stressing factors, from thermal cycling to moisture ingress, necessitating characterization and understanding of any potential degradation and failure modes. Additionally, accelerated testing methods are integral in order to develop and iterate new materials over shorter timescales. I therefore make use of elevated humidity exposures to explore the moisture-enabled degradation of antireflective coatings, as well as accelerated thermal cycling to characterize the evolution of stress and defects in metal gridlines. The first ever measurements of adhesion in these systems are made through the use of the newly developed composite dual cantilever beam test, which can also be broadly applied to any system that makes use of thin, brittle, or otherwise fragile substrates. In addition, I discuss the mechanical properties of silicon carbide thin film membranes, grown epitaxially upon silicon substrates. These films presently attract enormous interest as they enable fabrication of transducers with exceptional mechanical properties while also making use of well-established silicon micromachining techniques. The residual stresses developed during growth, as well as stresses developed during pressurization and fracture of these membranes are discussed, leading ultimately to better understanding of how these membranes might be used.
Thin-film crystalline solar cells for low capex manufacturing [electronic resource]
Keywords: Electrical Engineering.

High capital expenditure (CapEx) in manufacturing has become a major barrier to the sustainable growth of the photovoltaic (PV) solar cell industry. Therefore, it is crucial to develop new technologies that could enable low capex manufacturing in the PV industry. Among these, ultra-thin crystalline solar cell technology, with active semiconductor layers 10--100 times thinner than conventional solar cells, is a promising one, as it could both reduce both material consumption reduce capex and quite surprisingly, and enhance the energy conversion efficiency. In order to achieve high efficiency, it is important to reduce recombination with better passivation technology to increase voltage and improve light absorption through photon management to increase the current. The first half of this dissertation focuses on contact passivation using carrier selective layers. Although ultra-thin crystalline silicon (c-Si) solar cells could suppress bulk recombination and enhance Voc through better carrier confinement, the contact recombination at the unpassivated metal-semiconductor interface of the metal Ohmic contacts significantly reduces the Voc. An electron-selective TiOx layer is introduced for the n-contact, while a hole-selective NiOx layer is introduced for the p-contact. The carrier-selective effects of the two materials are evaluated through the design, fabrication and characterization of contact resistivity, which reveal the conducting effect for majority carriers and blocking effect for minority carriers. Also, contact recombination factor J0c is characterized for both layers, which demonstrate the contact passivation effect. In addition, the effect of rapid-thermal-annealing (RTA) is also evaluated under different temperature conditions. Finally, the NiOx layer is successfully integrated with a 2-μm thin-film c-Si solar cell, and the Voc is improved by 2-7 mV. The second part of this dissertation discusses the optical engineering and absorption enhancement in nanostructured solar cells. First, for the c-Si solar cells, the SiNx nanostructured dielectric layer is introduced as a new approach to design and fabricate whole-wafer nanostructures. The SiNx nanostructured dielectric layer is applied onto a 2.9-μm ultra-thin c-Si solar cell. The short-circuit-current (Jsc) of the cell is improved by 32% and the energy conversion efficiency is enhanced by 44%. Also, the SiNx nanostructured dielectric layer is integrated onto a commercial 40-μm ultra-thin c-Si layer, and its reflection loss is suppressed to below 5% over a wide spectral and angular range. Second, for crystalline III-V solar cells, the design and optimization of nanostructured window solar cells are described through a set of carefully designed experiments. In addition, a graded window layer design is demonstrated, which shows the importance of reducing the parasitic absorption and minority carrier loss inside the nanostructured window.
A thing is a hole in a thing it is not for string quartet [electronic resource]
Keywords: Music.

A Thing is a Hole in a Thing it is Not is the first in a series of modular works that scale the same 64 seconds of music according to a simple, iterative algorithm. This process governs all temporal and timbre parameters. In the string quartet exhibited here, a replicative process yields a rich and unique aural result in response to the strict application of compositional process.
Three essays in experimental economics [electronic resource]
Keywords: Economics.

The first chapter estimates the dynamic effects of credit availability on consumer borrowing and spending decisions using unique longitudinal data on consumer income, spending, balance sheets, and untapped credit, and a test-tube exogenous shock to credit availability. I design and implement a randomized trial at a European retail bank where I deliberately vary the credit lines of 54,522 pre- existing customers. I obtain four empirical results: (1) credit availability has a large and significant effect on spending and the use of credit; (2) this effect is not confined to a small set of credit constrained consumers; (3) increases in spending are concentrated in durables and services (e.g., health, education), made in the wake of positive income shocks; (4) credit line utilization displays mean-reverting dynamics, i.e. strict credit constraints are transitory. In the second chapter, I use the findings provide novel tests of competing models of intertemporal behavior. The findings rule out a simple permanent income model, a range of myopic models (e.g., rule-of-thumb, impatient), models where forward looking agents face a binding credit constraint and the baseline buffer-stock model. On the contrary, findings indicate that the primary affects of credit shocks is on consumers whom are not strictly constrained, through a portfolio problem. I then builds a partial equilibrium incomplete markets model with illiquid durables, and uses the endogenous ex- post heterogeneity to deliver many aspects of the magnitude, heterogeneity, composition and the dynamics of the marginal propensity to consume out of liquidity quantitatively. The third chapter, joint work with Jim Andreoni, Blake Barton, Doug Bernheim and Jeffrey Naecker, studies how people think about fairness in settings with uncertainty: one view holds that fairness requires equality of opportunity; another holds that it requires equality of outcomes. We conduct a laboratory experiment designed to determine which perspective people adopt, and under what conditions. We find that most people view fairness from an ex ante perspective when making decisions ex ante, and from an ex post perspective when making decisions ex post. As a result, they exhibit the hallmark of time-inconsistency: after making an initial plan that is fully state-contingent, they revise it upon learning that certain states will not occur. These patterns are robust and persist even when people are aware of their proclivities. We argue that these patterns are best explained by a theory of nominal fairness.
Three essays in the economics of health care and education [electronic resource]
Keywords: Economics.

This dissertation explores a number of issues in the economics of education and health care. The first chapter, co-authored with Bassam Kadry, M.D., Joseph Orsini, Igor Popov, and Christopher Press, M.D., starts by noting that a large body of literature argues that a large fraction of the increasing health care costs in the United States is due to the increasing prevalence of obesity. Yet most of these studies focus only on the degree to which obesity is correlated with the number of procedures an individual undergoes. If obesity also increases the cost of a procedure, the previous estimates understate the medical cost of obesity. We illustrate this point in the context of hip replacement surgery. We find that obesity does increase the cost of surgery and that ignoring this margin underestimates the cost of obesity by approximately 5%. This suggests that potential savings from obesity reduction programs are larger than previously thought. In the second chapter, I use the fact that multiple elementary schools feed into the same middle school to demonstrate that the positive impact that teachers have on their own students spills over to affect their students' future peers. Although this indirect effect on any particular individual is small, a teacher impacts many more students indirectly than directly, so the indirect value is a sizable portion of a teacher's total value; I find that ignoring teachers' indirect effects underestimates their value by roughly 35%. Because the spillovers also affect teacher value added estimates, I develop a method of moments estimator of teacher value added that accounts for the spillovers and show that accounting for the spillovers does not have a large impact on the ranking of teachers in New York City. I conclude by showing that the spillovers occur within groups of students who share the same race and gender, which highlights the crucial importance that the social network plays in disseminating the effect. Finally, the third chapter, co-authored with Michael Dinerstein, attempts to shed some light on how incentivizing teachers to increase their students' test score affects the way teachers behave, since this is an extremely important input to many education policy decisions. Exploiting a dramatic change in the way teachers in New York City were granted tenure, we provide evidence that incentivizing teacher value added leads to small but statistically significant increases in the teachers value added scores. This increase, however, comes at a cost: the test score gains these teachers cause in their students fade-out more rapidly than similar gains caused by non-incentivized teachers, which suggests a change in the way incentivized teachers direct their attention. Yet, at this point, both of these effects appear small relative to the potential changes this policy could have on the teachers entering and exiting the profession.
Three essays on industrial organization [electronic resource]
Keywords: Economics.

This dissertation examines a few empirical questions industrial organization and economics of innovation. Chapter 1 studies mobile app industry. More specifically, success breeds success in many mass market industries, as well known products gain further consumer acceptance because of their visibility. However, new products must struggle to gain consumer's scarce attention and initiate that virtuous cycle. The newest mass market industry, mobile apps, has these features. Success among apps is highly concentrated, in part because the "top apps lists" recommend apps based on past success as measured by downloads. Consequently, in order to introduce themselves to users, new app developers attempt to gain a position on the top app lists by "buying downloads, " i.e., paying a user to download the app onto her device. We build a model to rationalize this rational, that accommodates the impact of buying downloads on top list ranking, and optimal investment in buying downloads. We leverage a private dataset of one platform for buying downloads and identify the return on this investment, as a test for the assumption of the model.
Three essays on international trade networks [electronic resource]
Keywords: Economics.

This dissertation studies the formation of free trade agreements (FTAs) as well as the effects FTAs have on international trade. The first essay examines the "dynamic time-path question" raised by Bhagwati (1993), whether preferential trade agreements help or hurt the attainment of global free trade in the long run. Earlier works done on this topic take a stance on a trade model and ask whether global free trade is a unique pairwise stable network. I build upon this approach and, instead of taking a stance on a specific trade model, argue that all trade models employed in these earlier works fall into the same class of model, which is characterized by three simple properties. Under these properties, it can be shown that all pairwise stable networks are networks with complete components of unique sizes, and the size of each component is bounded above by a function of the next largest component. In particular, under these three properties, global free trade is always pairwise stable. Being able to characterize the set of all pairwise stable networks, a natural question to ask is, starting from some network configuration, which pairwise stable network is more likely to arise. The second essay develops a method to calculate the probability of reaching each pairwise stable network given any value function that is symmetric for all players. I then demonstrate the approach by applying it to two network formation games and compare the results with existing analyses. The third essay is empirical in nature. It explores how exporters with different characteristics respond differently to a unilateral reduction in trade cost in the foreign country. In doing so, the paper develops a two-tier product space (industry and product) that allows for a richer prediction of the trade pattern. Using a novel data set on Thai exporters' responses to Vietnam's tariff reductions in 2001--2008, I find that while all exporters respond to foreign tariff reduction on the intensive margin, they respond differently on the extensive margin. While large firms tend to introduce products within the industry they already have presence in, small firms tend to start exporting products in new industries. This suggests that the cost curve is concave in the product dimension, but is convex in the industry dimension.
Three essays on organizational politics, search, and learning [electronic resource]
Keywords: Business.

My dissertation consists of three papers that develop new theory at the nexus of organizational politics and organization learning. Each paper attempts to integrate the disparate approaches to group decision-making in organizational theory and political economics. The first paper examines how preference conflict in organizations impacts the likelihood that organizations will learn about the performance of existing policies prior to making changes to organizational strategy. The second paper looks at how career concerns of managers inside of organizations impact the character and informativeness of offline experimentation. The third paper uses existing theory on delegation and informational influence in political economics to better understand how social movements utilize policy expertise to get access to the political process.
Thresholds of Masculinity: Understanding how to act and dance “like a man"
Keywords: Masculinity
hegemony
gender
dance
ballet
performance
stereotypes
feminism
feminist
patriarchy
masculine pressures
Thesis

In recent years, studies have explored the influence of hegemonic masculinity on boys’ identity development, and shown that masculine pressures idealize emotional stoicism, encourage aggressiveness, and threaten mental wellness among boys (Kenway et al., 1997; Coyle et al., 1998; Way et al., 2014; Chu et al., 2014). The purpose of this study was to explore the salience of hegemonic masculinity for male ballet dancers within the context of their training and how this impacts the ways they view themselves as dancers and as men. My findings suggest that dance, being a context where a more fluid masculinity can be preformed, may offer a means of resisting hegemonic masculinity norms. However, my findings also suggest that the benefits of dance are contingent on the dancer’s ability to overcome manifestations of conventional masculinity within the dance studio as well as within society. While these manifestations seem to influence the social wellbeing, body image, and self-esteem of every male dancer, the extent of this influence seems to vary between dance styles and across generations. This paper concludes with a discussion on how dance training can be modified to be more supportive of male dancers’ wellness and help validate alternative masculinities.
Time- and momentum-resolved nanoscale thermal transport [electronic resource]
Keywords: Applied Physics.

There is a growing need for materials with non-traditional transport properties. For example in microcircuits, materials that can dissipate heat rapidly while acting as electrical insulators are sought for efficient heat sinks. Thermoelectric materials, useful for converting waste heat into electricity and for providing all solid-state (coolant-free) refrigeration, demand the exact opposite: thermal insulators with large electrical conductivities. Thus there is interest in ways to tailor the thermal transport properties independent of electrical properties. Currently ways to probe the microscopic physics underlying thermal transport in solids, however, are restricted to external mechanisms, for example contact-based transport measurements or non-contact thermoreflectance imaging. X rays on the other hand, because of their penetrating power, are able to explore the details of thermal transport below the surface. Along these lines, we developed means of using time-resolved x-ray diffraction to probe microscopic thermal transport in materials with embedded nanoparticles, across thin-film interfaces, and in working miniaturized thermoelectric devices. In this thesis we describe several experiments utilizing x rays from storage rings and free electron lasers to explore thermal transport in the time domain via the pump-probe technique.