VictorJuiz/thesis huggingface dataset:
Understanding particle migration, margination and adhesion in cellular suspensions

In this thesis, we develop a theoretical framework for red blood cell migration, platelet margination and adhesion in pressure-driven channel flow based on the hydrodynamic principles of particles in Stokes flow and the kinetic information on platelet adhesion under arteriole flow conditions. We also perform simulation and experimental studies to verify our theoretical predictions. We identify deformability-induced lift force and shear-induced diffusion as governing mechanisms for the cross-flow transport of red blood cells. The absence of a lift force for rigid platelets is the key to their margination. We explore the steady state and non-equilibrium behaviors of particle migration and margination and consider the scenarios of rigidified red blood cells due to malaria infection and migration in small arterioles. We also investigate the effects of flow properties (e.g. shear rate) and platelet properties (e.g. receptor densities) on platelet adhesion. We elucidate the role of particle deformability in changing the microstructure of such suspensions in wall-bound channel flow. Therefore we emphasize the role of red blood cell volume fraction (hematocrit) on the rates of these three processes which ultimately lead to hemostasis and thrombosis.

Keywords: Chemical Engineering.
Advisor: Shaqfeh Eric S. G. (Eric Stefan Garrido) 
Fuller Gerald G.
Qin Jian (Professor of Chemical Engineering)
Understanding provenance signatures in active margin settings : modern central California and the the magallanes-austral foreland basin, Southern Patagonia

From plate tectonics that act over thousands of kilometers and millions of years to sedimentary processes that operate over sub meter and sub annual timescales, provenance data integrates many types of information. The research in this dissertation attempts to advance the understanding of tectonic and sedimentological controls on provenance analysis by examining one modern and one ancient example. The modern example, coastal central California provides the advantage of being a well-studied modern setting for which boundary conditions of source region geology and sediment dispersal patterns are constrained. In the ancient example, the Magallanes-Austral retroarc foreland basin in southern Patagonia, considerable initial work was required to constrain the stratigraphic framework of the basin before provenance patterns and sediment dispersal could be examined in detail. Chapter 1 explores sediment dispersal off the modern coast of central California in an attempt to determine how sediment pathway partitioning and sediment mixing control the expression of provenance signatures. This chapter demonstrates that sediment mixing in the marine realm is an important control on provenance signatures and that submarine canyons and coastal geometries dictate the way sediment dispersal systems are partitioned along narrow-shelf margins. Chapter 2 provides a stratigraphic framework for the Magallanes-Austral foreland basin through field mapping and detrital zircon maximum depositional age calculations. This framework provides the first radiometrically-age-controlled, unified, framework for the basin between 49.5⁰S and 52⁰S. The focus of the chapter is constraining the age of the Cerro Fortaleza Formation. This unit had previously been assigned ages ranging from Cenomanian to Maastrichtian. Using detrital zircon maximum depositional ages we constrain the age of the unit to Campanian to Maastrichtian. Refining the age of this unit allows the rest of the stratigraphic framework of the basin to be defined. Chapter 3 is a provenance analysis of the Magallanes-Austral retroarc foreland basin that incorporates previously published provenance data from the basin along with 28 new detrital zircon and 34 new sandstone petrography samples. This analysis is informed by the systematic incorporation of geologic background information with an attempt made to describe sediment dispersal patterns from the whole-basin scale down to individual sediment dispersal systems.

Keywords: Geological and Environmental Sciences.
Advisor: Graham S. A. (Stephan Alan)
Grove Marty
Lowe Donald R.
Understanding the functionality and dimensionality of vector embeddings : the distributional hypothesis, the pairwise inner product loss and its applications

Vector embedding is a foundational building block of many deep learning models, especially in natural language processing. We present a theoretical framework for understanding the effect of dimensionality on vector embeddings. We observe that the distributional hypothesis, a governing principle of statistical semantics, requires a natural unitary-invariance for vector embeddings. Motivated by the unitary-invariance observation, we propose the Pairwise Inner Product (PIP) loss, a unitary-invariant metric on the similarity between two embeddings. We demonstrate that the PIP loss captures the difference in functionality between embeddings, and that the PIP loss is tightly connected with two basic properties of vector embeddings, namely similarity and compositionality. By formulating vector embedding algorithms as matrix factorizations under noise, we reveal a fundamental bias-variance trade-off in the dimensionality selection process, which, similar to many signal processing problems, is between the signal and noise power. This bias-variance trade-off sheds light on many empirical observations which have not been thoroughly explained, for example the existence of an optimal dimensionality. Moreover, we discover two new results about vector embeddings, namely their robustness against over-parametrization and their forward stability. The bias-variance trade-off of the PIP loss explicitly answers the fundamental open problem of dimensionality selection for vector embeddings. The combination of vector embedding and the PIP loss can be applied to quantify diachronic evolution and domain adaptation of language. We develop the Global Anchor Method (GAM), a method for comparing embeddings trained on two different corpora. Corpora dissimilarity determines model transferability, namely, whether a model trained on one corpus will work on another. We used GAM to analyze diachronic and domain effects in English corpora, using the Google Books and arXiv datasets as examples, where we reveal interesting sociological and academic factors that affect the usage of language.

Keywords: Electrical Engineering.
Advisor: Prabhakar Balaji
Rosenblum Mendel 
Weissman Tsachy
Understanding the impact of conversational AI on supportive interactions : towards the CARE (Conversational AI and Response Effects) model

In supportive interactions, people reveal their negative emotions and struggles to another person, who listens and responds with the goal of relieving distress. The nature of the responses from the partner can determine how well the conversation reduces distress, with validating responses being beneficial and invalidating being harmful. Yet new dynamics may emerge, causing different effects, with a conversational AI partner, such as a chatbot, rather than another person. This dissertation has two main portions. The first is an empirical study that used an experimental design to test whether the type of response (validating vs. invalidating) and perceived identity of the partner (chatbot vs. human) changed the effects of supportive interactions. The results suggest that for one component -- proximate reactions -- only the type of response, but not the identity of the partner, mattered. The other two components -- disclosure behavior and future well-being - raised new dynamics and different outcomes depending on the partner's identity. The second part of the dissertation is the introduction of a model of partner effects (CAI vs. human) in supportive interactions based on these findings and on past work.

Keywords: Communication.
Advisor: Hancock Jeffrey
Bailenson Jeremy 
Landay James A.
Reeves Byron
Understanding trigonometric relationships by grounding rules in a coherent conceptual structure

Mathematical cognition relies on a variety of representations, from algebraic rules to diagrams that convey the meaningful relationships expressed in the algebraic rules. My dissertation shows how a diagram that captures the conceptual structure underlying the domain of trigonometry can make symbolic expressions into more meaningful rules that can be applied and generalized successfully. We presented students with trigonometric identity problems, and examined the representations they used. Students most often reported using the unit circle, a diagram that captures the meaning of trigonometric expressions in an integrated way. Those who reported using the unit circle also tended to have higher accuracy. Other students, who did not report using the unit circle or reported using it less often, were more likely to rely on heuristics and rules that had no connection to the meanings of the trigonometric constructs involved. We created a formal rule-based lesson and another lesson which instead grounded relationships in the unit circle, and we randomly assigned students to each lesson. Students in the grounded lesson condition showed improved accuracy both on problems taught in the lesson and on problems held out for transfer. While the unit circle could be used simply as a standalone procedure to solve problems, some students appeared to apply an understanding of the relationships and symmetries in the unit circle to extend and combine rules. Students reported relying slightly more on a rule or formula when solving taught problems than transfer problems. However, across all problem types, students often reported relying on both the unit circle and a rule or formula on a particular problem. As students gained experience solving problems after the grounded lesson, they tended to reduce their active use of the unit circle, as indicated by their self-reported strategies and by their interactions with an external unit circle tool. Across our studies, the unit circle revealed itself to be a strong, coherent conceptual structure, and it creates a fertile ground for learning and understanding trigonometry through the interplay of visuospatial and rule-based approaches. Students learn how to map parts of a symbolic expression onto meaningful properties of the unit circle, and this grounded understanding facilitates application and generalization of rules in order to solve problems successfully. Helping students from all backgrounds master these grounded rules remains a challenge for teachers and cognitive psychologists.

Keywords: Psychology.
Advisor: McClelland James L. 
Frank Michael C. (Professor of human biology) 
Schwartz Dan
Unequal contexts, unequal opportunity [electronic resource] : racial differences in school achievement distributions and neighborhood socioeconomic status

Racial school and residential segregation mean that black students in schools, and black families in neighborhoods generally face different school and neighborhood contexts, respectively, than their white counterparts. These patterns persist despite decades of declining residential segregation, and court-mandated school desegregation. Just how different school and neighborhood contexts are, however, is an open question. This dissertation utilizes a novel approach to measuring racial differences in school and neighborhood context to answer this question. The first paper uses an exposure measure to describe the student achievement distributions in the schools of different race students, conditional on achievement. A similar measure is used in the second paper, which describes differences in neighborhood socioeconomic status for families of the same income, but different races. Both papers find that, even conditional on achievement, in the case of schools, and family income, in the case of neighborhoods, black students and families face strikingly different contexts than white students and families. The final paper of the dissertation links a version of the neighborhood measures to young adult outcomes to explore how differences in neighborhood context area associated with income, college-going, and teen pregnancy. Results suggest that neighborhood context matters for college enrollment and teen birth rates, while the evidence for adult income is less conclusive.

Keywords: Education.
Advisor: Reardon Sean F. primary advisor. Thesis advisor
Bettinger Eric advisor. Thesis advisor
Domingue Ben advisor. Thesis advisor
Loeb Susanna
Unforeseen geochemical and hydrological triggers of arsenic release during managed aquifer recharge

Managed aquifer recharge (MAR) is an increasingly applied groundwater storage method to enhance freshwater security and increase resilience to climate extremes. MAR projects are commonly implemented via infiltration or injection of various types of source water into underlying groundwater aquifers. Benefits of MAR extend beyond enhancement of local groundwater supplies; they can provide seawater intrusion barriers, enhance ecosystem services, maintain aquifer capacity and minimize subsidence. Despite the numerous potential benefits, artificial recharge can also adversely impact groundwater quality by altering the native geochemistry and triggering the release of toxic contaminants indigenous to aquifer sediments. Desorption or dissolution, and subsequent mobilization, of contaminants poses a principal challenge to maintaining local groundwater quality, and thus also to ensuring the viability of MAR as a water enhancement strategy. Arsenic imposes the most widespread threat, degrading water quality around the world, where it has deleterious impacts on human and ecosystem health. My research uses a combination of experimental, spectroscopic and modeling approaches to study the geochemical and hydrological causal mechanisms of As mobilization during groundwater recharge.

Keywords: Earth System Science.
Advisor: Fendorf Scott 
Freyberg David L. 
Gorelick Steven M.
Universal meshes for two-dimensional domains with piecewise C2-regular boundaries

We introduce a method to deform a mesh to conform to a domain with piecewise C2-regular boundary, by only moving a fraction of vertices of the given mesh. The method preserves all vertices and connectivities of the mesh, and only small regions near the boundary are deformed, which makes it computationally efficient. The most appealing application of the method is when it is needed to mesh a group of domains, such as the case of moving boundary problems. For such problems, a single mesh that does not require any conformity to the boundary can be generated, which is then used to obtain conforming meshes for a number of domains by simply deforming it. The challenge for such an application is the robustness of the method, which allows the method to be automated without any user intervention. We provide the method with conditions that guarantee its success, which can be either satisfied or checked a priori. The outline of the method is as follows. The boundary is first divided into a set of C2-regular curves, called segments. Some vertices near the endpoints of each segment are perturbed so that each endpoint has a vertex assigned to it. Then, a set of edges, called domain edges, are selected from the mesh, and the domain edges or their vertices are projected onto the boundary. Some vertices near the curve are perturbed to relax any distorted triangles. A crucial necessary condition for the method to render a conforming mesh with elements of good quality is that the projection of domain edges onto the boundary be a homeomorphism, which involves both choosing an appropriate set of domain edges and projection map. In our method, we choose the set of domain edges individually for each segment. This set is "roughly" the set of all edges joining the two vertices on a given side of the curve, of each triangle that has a third vertex on the other side. The domain edges are then projected to their corresponding segment via the closest point projection. The highlight of the strategy is the algorithm to assign an orientation to each segment, which determines the set of domain edges for the segment. The algorithm prevents domain edges of distinct segments from intersecting at point other than the endpoints of a segment. Certain conditions are also required on the mesh and the curve for the projection to be a homeomorphism. Some angles in the mesh are required to be acute, and triangles near the boundary should be sufficiently small with respect to its local radius of curvature of the curve. We analyze the method and present theorems that show the conditions that guarantee the homeomorphism of the projection. The conditions solely depend on the features of the given boundary, and can be computed in advance to generate the background mesh, if needed.

Keywords: Mechanical Engineering.
Advisor: Lew Adrian 
Darve Eric 
Pinsky Peter M. (Peter Michael)
Unpopular Choices: A Cautionary Tale for the Future of Venezuela

After the death of Hugo Chavez and the rise of his handpicked successor Nicolas Maduro, Venezuelan began a rapid descent towards authoritarianism. However, the conditions that gave way to this chaos trace their roots beyond that of Chavismo and modern Venezuelan socialism. In 1958, political leaders with visions of democracy and liberal ideals united to oust a military dictator that ruled for the past decade. Together, they crafted a power sharing agreement in the Pact of Punto Fijo to ensure alternation of power among political parties and to curtail divisions on ideological issues. The pact survived for nearly five decades and weathered numerous coup attempts and a large Marxist insurgency. However, structural changes in the political institutions eventually weakened the pact and created the conditions for the rise of populism. All signs of democracy have evaporated since the Pact of Punto Fijo was signed sixty years ago. Now, opposition parties to President Maduro are fracturing and the Venezuelan armed forces remain closely tied to Maduro. However, with history as their guide, this paper argues that the opposition leaders should maintain strong coordination among themselves and identify moderates within the armed forces that will be essential when the transformation back to democracy begins. It will review the historical process which brought about democracy in the mid-twentieth century. It will subsequently review the structural transformation of the political institutions and how it created the conditions for the breakdown of democracy. It will conclude with a contemporary assessment of the current political situation and put forth an unpopular recommendation.

Keywords:  Center for Latin American Studies
Stanford Center for Latin American Studies
Latin America
Venezuela
democracy
political institutions
armed forces
policy making process
Pact of Punto Fijo
Thesis
Advisor: Weinstein Jeremy
Unruly Proxies: Why States Sponsor Non-State Actors That Threaten Their Interests

Authoritarian regimes in Muslim-majority countries sometimes fund proxy groups at a significant cost to their own stability. States can lose control of the proxy groups they support, or a state’s policy decisions can drive a wedge between the sponsor and the proxy, pitting them against one another. Frequently, and sometimes disastrously, proxy groups “bite the hand that feeds them” and turn on their sponsors. In some cases, the state continues to support a proxy group after the group has defected on its sponsor. These puzzling relationships prompt a question previously unexplored in the literature: Why do states support proxy groups that threaten their interests? In this thesis, I use process-tracing to analyze several case studies involving state support of a proxy that has defected on its sponsor. Ultimately, I conclude that states support non-state actors that threaten their interests when three conditions are present: the relationship between the state and the proxy group is public, the proxy is popular with key domestic coalitions and the general public, and the group is strong enough to retaliate against the state. My research sheds new light on the role of domestic politics in state sponsorship of terrorism.

Keywords:  Center for International Security and Cooperation
Stanford University
Center for International Security and Cooperation
CISAC
terrorism
proxies
sponsorship
Middle East
terror financing
Kashmir
Fatah
al-Qaeda
Saudi Arabia
Pakistan
Syria
Israel
Thesis
Advisor: Blaydes Lisa
Unsupervised learning for residential energy consumption analytics

Developing strategies to encourage reduction in households energy consumption requires utilities to categorize, predict and modify consumers electricity usage. Unfortunately, a typical consumer exhibits wide variation in daily 24-hour electricity usage patterns. Traditional clustering methods have resulted in many hundreds of clusters, with a given consumer often associated with several clusters, making it difficult to classify consumers into stable representative groups and to predict individual electricity usage patterns. This dissertation presents two methods that better cluster consumer electricity usage pattern. The first method uses Dynamic time warping (DTW), which seeks an optimal alignment between electricity usage patterns. The second method assumes that electricity usage composes of a sequence of blocks generated from electrical devices. The clustering uses a novel block factorization model that embeds consumer usage pattern into a low dimensional space that flexibly captures time shifts of usage. Compared to commonly used clustering algorithm, both methods result in a more distinct set of clusters, and on average, a given consumer associates with a fewer clusters. The ideas and results from clustering is then used for individual electricity usage prediction. Prediction is done at two levels. The first level is day-to-day prediction where the shape of next day electricity usage pattern is predicted by cluster representatives from DTW. The second level is finer grain prediction based on block idea where load curve is predicted through block sequences. Predictions at both levels result in lower prediction error compared to some popular load forecasting techniques.

Keywords: Electrical Engineering.
Advisor: Lall Sanjay 
O'Neill Daniel C. (Daniel Craig)
Van Roy Benjamin
U.S.-China Cybersecurity Relations 2011-2017: Analyzing differences of approaches and stability

This thesis examines the development of cybersecurity approaches of both the U.S. and Chinese governments and their stability in cyberspace between 2011-2017. This thesis argues that deterrence postures of U.S. and China has been affected by each other’s behaviors during major events in recent years and that certain level of stability exists albeit some risk of misperception.

Keywords:  Stanford Global Studies
Stanford Global Studies
East Asian Studies
cyber security
China
United States
Thesis
Advisor: Miller Alice Lyman