VictorJuiz/thesis huggingface dataset:
Monitoring and modeling the elastic and transport properties of organic-rich marl during maturation through pyrolysis experiments
Keywords: Geophysics.

Organic-rich marl is an important type of shale reservoir because its stiff matrix leads to relatively high permeability and frackability compared to clay-rich shale. However, how the stiff matrix affects the changes in the elastic and transport properties of organic-rich marl during maturation remains poorly understood, obstructing the remote characterization of this reservoir type across different maturity levels. One major cause of the poor understanding is the lack of rock physics a dataset tracking the changes in these properties as a function of maturity. To overcome this obstacle, I induced ex-situ maturation of core plugs from Eagle Ford marl by conducting confined pyrolysis experiments in fine-steps across all maturity windows from the immature through the early-peak oil, late oil, wet gas, and finally the dry gas window. The confined pyrolysis provides a confining pressure during maturation, imitating lithostatic pressure in the subsurface condition. This is a key improvement over previous unconfined pyrolysis experiments in which unrealistically large aperture fractures developed during pyrolysis. After each of my pyrolysis runs, I monitored the changes in microstructure, porosity, velocity, permeability, and geochemical properties. The results show systematically decreasing kerogen volume, increasing porosity, decreasing velocity, and increasing permeability as maturation progresses. These results reveal that secondary porosity from the loss of kerogen volume is the predominant microstructural alteration and the primary driver for decreasing velocity and increasing permeability. Based on these findings, I developed an elastic model for organic-rich marl that incorporates the maturation process. I used the pyrolysis dataset from this study along with previous petrographic and nanoindentation studies to calibrate a few ill-defined parameters in the model—such as kerogen porosity and the moduli of kerogen—as a function of maturity. These parameters cannot be directly measured and their estimated values in the literature are too sparse to be used in the calibration alone. Lastly, I employed the calibrated elastic model to build a rock physics template for characterizing organic-rich marl based on their elastic properties. I tested the applicability of the template against a rock physics dataset from natural (in-situ) maturation. The dataset comprises Bakken, Eagle Ford, and Niobrara core plugs and 11 Eagle Ford well logs across different maturity levels. The test results show that the template is able to map the scatter in the elastic properties of the naturally matured dataset to the variations in maturity, kerogen content, lithology, and fluid saturation. Therefore, this thesis provides a coherent pyrolysis dataset, a rock physics model, and a rock physic template for characterizing the properties of organic-rich marl across different maturity levels
Morphisms and cohomological comparison for Henselian schemes
Keywords: Mathematics.

The global analogue of a Henselian local ring is a Henselian pair - i.e., a ring R and an ideal I which satisfy a condition resembling Hensel's lemma regarding lifting coprime factorizations of polynomials over R/I to factorizations over R. The geometric counterpart is the notion of Henselian schemes, which can serve as an "algebraic" substitute for formal schemes in applications such as deformation theory. In this thesis we discuss Henselian schemes and quasi-coherence in detail, including the correction of an error in the existing literature concerning quasi-coherent sheaves on affine Henselian schemes. We also develop the theory of smooth and etale morphisms of Henselian schemes and prove that quasi-coherent sheaves on Henselian schemes are sheaves for the Henselian-etale topology. Finally, we prove a GAGA-style cohomology comparison result for Henselian schemes in in positive characteristic, and discuss algebraizability of coherent sheaves on the Henselization of a proper scheme
Motion artifact mitigation in magnetic resonance angiography
Keywords: Electrical Engineering.

Magnetic Resonance Imaging (MRI) is a safe, effective, and non-invasive method for examining the human body with excellent soft-tissue contrast. However, because of prolonged scan times, MRI is particularly sensitive to motion. Motion can arise from any number of sources, including respiration, pumping action of the four cardiac chambers, and even sudden involuntary patient movement. This dissertation describes several novel strategies to reduce motion artifacts in cardiovascular magnetic resonance angiography (MRA), which encompasses a class of techniques to image blood vessels with high contrast
Multi-fidelity wing optimization utilizing 2D-to-3D mapping in transonic conditions
Keywords: Aeronautics and Astronautics.

Due to time and resource constraints, the conceptual design process for new aircraft is typically limited to the use of inexpensive low-fidelity methods. Unfortunately, these methods generally only provide the fidelity necessary to confidently go forward with a new design when they have been calibrated to previous aircraft of similar type and the design space does not include significant non-linearities. This substantially limits the application of new technology early in the design cycle, and means that only high-level information can be obtained, potentially limiting the available design space. To remedy this, new methods must be developed that can produce higher-fidelity results without a significant increase in cost. Here, a method is proposed for higher-fidelity aerodynamic analysis that incorporates 2D and 3D pressure distribution mapping into a multi-fidelity framework. This expands on previous work in the area by providing a multi-fidelity approach that allows for the prediction of the shape of the pressure distribution in addition to the level of aerodynamic performance. The novel methods presented are a procedure for smooth identification of transonic feature points, and an extension of shape-preserving response functions to include derivative information. To demonstrate their application, results are presented for a wing that has been optimized using the 3D solver FLO107 exclusively, as well as a combination of the 2D solver FLO103 and FLO107. The differences in required evaluations and the final results are documented, showing the potential for significant computational savings in both direct optimization and inverse design
Multi-modal integration in number sense acquisition
Keywords: Psychology.

Mathematical concepts usually have multiple representations. Even the simplest mathematical concepts, such as natural numbers, can be grounded in various ways. Different representations of natural numbers are supported by diverse sensorimotor modalities. How do children learn to integrate representations of numbers from different modalities like visual, verbal, motion and gestures? In fact, this flexible mapping between different representations of natural numbers is an important component in numeric knowledge development, such as counting number of objects in a set (mapping cardinality to number word), naming an Arabic numeral (mapping written number symbols to verbal number words), number line estimation (mapping number words to positions on a number line), etc. In this PhD work, we systematically answer this question by building neural network models that simulate the learning procedure underlying diverse numeric processing tasks and thus account for multi-modal integration in number sense acquisition. It explains why symbolic numbers demonstrate similar properties as non-symbolic numbers, why training children on non-symbolic number arithmetic results in improvement on symbolic arithmetic and how they learn to selectively attend to different aspects of a number and processing numbers according to different instructions. Furthermore, we apply our model to a situated learning scenario, the number board game (e.g., Siegler and Ramani (2008)). We use our model to explain why playing the number board game leads to improvement in various basic number-related tasks, including numeral identification, magnitude comparison, counting, number line estimation, etc., and how such cross-task transfer happens. Our model provides a unified framework that simulates a diverse set of numeric processing tasks. Overall, it offers computational accounts for various empirical findings in the number cognition literature and deepens our understanding of the underlying mechanism in number sense acquisition
Multipath detection and mitigation in urban environments
Keywords: Aeronautics and Astronautics.

The Global Navigation Satellite System (GNSS) has become more and more widely used in commercial applications such as smart phones, cars, and drones. GNSS is one of the core technologies used for automotive navigation. For consumer automotive applications, it is typically the only navigation system that provides precise absolute positioning and timing. As transportation technology moves towards greater autonomy, the need for and the reliance on precise GNSS with integrity becomes increasingly urgent. For terrestrial applications, multipath becomes the biggest challenge having GNSS with high accuracy and high integrity. This work explored and examined several approaches to detect and mitigate multipath using newly available resources and technologies. A multipath detection method using three- dimensional (3D) building model with statistical ray tracing was developed that provides better resilience toward initial user position error than deterministic ray tracing and does not rely on redundancy in received GNSS measurements. A multipath mitigation method using multi-frequency signals was also developed that leverages the new civil signals and the correlation in multipath characteristics between different frequency signals from the same satellite to estimate and remove multipath effect on correlation function. Finally, a mapping methodology to infer obstacles in the environment using obscured and unobscured rays was proposed and algorithms were developed to generate 3D maps using GNSS measurements
Multipolar order and fluctuations in TmAg2 and YbRu2Ge2
Keywords: Applied Physics.

In this thesis we will show thermodynamic and transport properties of two 4f intermetallic materials, YbRu2Ge2 and TmAg2. Both of these materials have been proposed to undergo ferroquadrupolar phase transitions in the B1g symmetry channel, at 10.2K and 5K respectively. The B1g elastoresistivity and low-temperature X-ray measurements of YbRu2Ge2, and the strain-tuning of the phase transition for TmAg2 as inferred from the elastocaloric technique, that are presented here establish that this is indeed the case for both of these materials. We investigate in detail how both of these ferroquadrupolar phase transitions can be/are suppressed towards a quantum phase transition at 0K, through the application of a magnetic field applied along the c-axis at 21.3T and 3.1T for YbRu2Ge2 and TmAg2 respectively. The quadrupole-strain susceptibilities of these materials are investigated throughout their respective H-T phase diagrams (using two different complimentary probes), revealing higher-order octupolar couplings in YbRu2Ge2, and a transverse-field mean field Ising susceptibility for the quadrupole-strain susceptibility of TmAg2. Resistivity measurements indicate potential signatures of quantum criticality in the proximity of the field-suppressed ferroquadrupolar phase transition for YbRu2Ge2
Multiscale approaches to study the biophysics of parasites and plankton
Keywords: Mechanical Engineering.

Multi-scale interactions of motile microorganisms with their environment are crucial in understanding disease transmission, as well as the ecology and biophysics of our oceans. This theme underlies the two problems I tackle in this thesis. The first part of the thesis is focused on the schistosomiasis parasite which currently infects 200 million people world-wide, with 700 million more at risk. Infection occurs when the free-living, motile stage of the parasite known as cercariae swim through fresh-water and infect human hosts by penetrating the skin. The swimming motility of cercariae is therefore crucial to disease transmission but is not well understood emphasizing an urgent need for research efforts. Towards this I combined biological experiments, with robotics and mathematical models to uncover how cercariae use their unique forked-tail to generate a robust and efficient "T-swimmer" swimming gait. Further I discuss results from our model and experiments which point to specific degrees-of-freedom that cercariae create that are crucial for their swimming efficiency, suggesting novel drug-targets for disrupting host-seeking. Studying schistomiasis cercariae in their native, ecological setting of ponds, rivers and lakes in Madagascar revealed an unsolved experimental challenge in studying such multiscale problems in the lab. Significantly, this challenge is also present in studying microscale biophysical processes in the ocean: how to measure single cells and organisms, at microscale resolution, while allowing them to freely move over ecological-scales (hundreds of meters) along the axis of gravity? To address this, I invented "Scale-free Vertical Tracking Microscopy", based on a "hydrodynamic-treadmill for single cells" with no bounds for motion along the axis of gravity. Using this method to bridge spatial-scales, I assembled the first multi-scale behavioral dataset of freely-swimming planktonic cells and organisms. Using this tool, I also demonstrate a "virtual-reality system for single cells",  wherein cell behavior directly controls its ambient environmental parameters and vice versa, enabling novel quantitative behavioral assays. The microscopy platform is built using open-source hardware and software components and has further been deployed in field settings such as marine stations in Puerto Rico, Monterey as well as oceanic research-vessels. This ability to bring the lab to the ocean has resulted in new discoveries such as rapid buoyancy modulation over millisecond timescales in planktonic diatoms as well as discovering gravity-oriented swimming behaviors among 8 phyla across the tree-of-life. This microscope and the results presented, exemplify a new paradigm of multi-scale measurement wherein one can observe macroscale, ecologically relevant phenomena at microscale resolution
Nanophotonic platforms for enhanced chiral light-matter interactions
Keywords: Materials Science and Engineering.

Chiral, or "handed, " structures range from spiral galaxies to human hands to amino acids to circularly polarized light (CPL). The differential absorption between right and left CPL, known as circular dichroism (CD), is critical to applications spanning the synthesis and purification of pharmaceuticals and agrochemicals to all-optical magnetic writing and recording. However, differential absorption of CPL is generally up to five orders of magnitude below the absorption of unpolarized light. Recent advances in nanophotonics, the study and manipulation of light at the nanoscale, lay the foundation toward highly sensitive and efficient CD. In this thesis, I will describe progress we have made to leverage these nanoscale chiral light-matter interactions in molecular and magnetic systems using high-refractive index periodic nanostructures, known as metasurfaces. First, we computationally design a platform based on dielectric nanodisks that enhances the local optical chirality density by engineering the coupling between electric and magnetic optical resonances. These high-index dielectric nanoparticles can enable large-volume and uniform-sign enhancements in the optical chirality density. By overlapping electric and magnetic resonances, local chiral fields can be enhanced by several orders of magnitude. We show how these design rules can enable high-yield enantioselective photochemistry and project a 2000-fold improvement in the yield of a photoionization reaction. Next, I will discuss an experimental demonstration of metasurface-enhanced circular dichroism with a molecular monolayer. We fabricate silicon nanodisk metasurfaces and functionalize them with a self-assembled monolayer of dye-DNA complexes. We measure the monolayer fluorescence-detected circular dichroism in a home-built table-top polarization sensitive spectrometer; we also show how this technique is sensitive to changes in the CD handedness through double-stranded to single-stranded DNA denaturing. Finally, we extend this platform for use in all-optical information storage applications using magnetic materials. We show that the presence of helicity-preserving silicon nanodisks can enhance reflection and transmission dissymmetries under right- and left-CPL excitation, leading to higher differential local absorption and thus the potential to decrease power thresholds and miniaturize components in magnetic switching
Nanophotonic thermal, plasmonic and non-hermitian media : from fundamental limits to applications
Keywords: Electrical Engineering.

Optics and photonics play a central role in modern science and technology, spanning renewable energy, fundamental science, consumer technology, sensors, therapeutics and medicine, global communication and information processing pipelines, and exciting new frontiers in quantum computing and artificial intelligence. Despite their vast diversity, these applications are threaded by electromagnetism, thermodynamics and quantum mechanics. In this Thesis, we begin at the intersection of thermodynamics and electromagnetism, exploring the fundamental limits of renewable energy harvesting technologies utilizing the Sun and the vast, cold outer space as thermodynamic resources. Then, making a connection to nanophotonics, we consider how nanostructuring affects the efficiency of energy harvesters such as solar cells, developing a rigorous mathematical formalism to treat light trapping. Continuing in the vein of the thermodynamics of photonic devices, we then develop a novel optical refrigeration mechanism that arises from tailoring the thermal radiation from active photonic structures. Next, we explore the behavior of plasmonic systems in a novel regime, demonstrating the significance of quantum-plasmonic effects in preserving their thermodynamic validity. Lastly, we explore a novel class of active electromagnetic media that break Lorentz reciprocity, finding applications in information processing schemes
Nanoscale electrical and thermal interfaces to resistive memory devices
Keywords: Electrical Engineering.

Future computing systems need ultra-high storage densities for large volumes of data. Non-volatile resistive random-access memory (RRAM) based on metal oxides or phase-change materials could enable such high capacity with low latency. However, as memory cell dimensions are reduced to sub-10 nm scale, their contacts, interfaces, and self-heating can determine the memory device behavior and packing density, yet these are poorly understood. In the first half of my thesis, I will show that the electrical contact resistivity varies over 10 orders of magnitude depending on the memory material considered; cubic Ge2Sb2Te5 has contact resistivity near 10 mΩ⋅cm2 while contact resistivity to as-deposited HfO2 is as high as 0.5 MΩ⋅cm2, at room temperature. I will then showcase switching measurements on nanoscale memory devices and insights gleaned about the role of contact resistance. In the second half of my thesis, I will demonstrate some of the first nanoscale thermal measurements on resistive memory devices using scanning thermal microscopy. With a single-layer graphene as a top electrode, I show the most thermally intimate measurement of an RRAM filament to date and observe a device temperature rise > 300°C. Varying the thermal conductivity of electrodes over a 50x range, I investigate device-level heat spreading and conclude that Joule heating in a sub-10 nm filament can cause a temperature rise up to 200°C, even at a distance of 50 nm from a typical RRAM device. By comparison to simulations, I show that the filament itself can reach temperatures in excess of 1200°C within its hourglass-like sub-10 nm dimension geometry. This filament temperature strongly depends on the thermal boundary resistance at the filament-electrode interfaces. These novel insights point to the importance of nanoscale thermal engineering of the filament-electrode interfaces and of the electrodes to minimize array level thermal cross-talk and to enable ultra-high storage densities
Nations by the Numbers: Ethnoracial Data Collection and National Identity in the United States and France
Keywords: Program in International Relations
race
census
social identity
Thesis

The question of how large, multicultural democracies balance diversity and national identity is crucial in an age in which these countries are both continuously diversifying and witnessing a surge in xenophobic nationalism. The politics of data collection exists at the heart of this tension, as quantifying people based on race, ethnicity, or religion can imply government legitimation of social divisions. In the United States, counting citizens by race and ethnicity is extremely common, yet this same practice is forbidden by law in France. From the French perspective, ethnoracial census categories serve to advance group-oriented rhetoric and undermine a unified French national identity. The motivation for my research is to test this claim — does government collection of ethnoracial data have adverse effects on the coherence and strength of national identity? In addition to analyzing the history of ethnoracial data collection in the United States and France, I conduct a national survey experiment of Americans assessing how ethnoracial categorization impacts respondents’ feelings of national identity. Ultimately, I find that ethnoracial categorization influences the national identification of white and black Americans, an effect that I posit stems from a relationship between Americanness and whiteness.
Natural image processing in the primate retina
Keywords: Physics.

The retina is the first stage of the visual system, where light is absorbed and encoded in the spikes of neurons. Information from roughly 100 million photoreceptors is compressed to the outputs of roughly 1 million neurons, called retinal ganglion cells, that make up the optic nerve. This is the brain's only source of visual information, yet how the retina uses this limited bandwidth is not well understood. This is particularly true for natural vision in primates, despite its relevance for human health applications, as retinal research is primarily done in non-primate species using targeted, artificial stimuli. Here, large-scale, multi-electrode recordings are used to investigate natural image processing in the primate retina through the complementary lenses of encoding, where computational models are used to predict the responses of RGCs to natural stimuli, and decoding, or reconstruction, where the stimulus is estimated from the RGC responses