VictorJuiz/thesis huggingface dataset:
Synthesis and Characterization of Open-Metal Site Grafting to Metal- Organic Frameworks for Solid Electrolyte Applications
Keywords: Metal-organic framework
solid polymer electrolyte
solid electrolyte
MOF-74
MOF
single-crystal XRD
PXRD
energy storage
battery
ion transport
lithium ion
lithium-ion grafting
grafting
single-ion transport
Thesis

In order for clean energy use to become a significant fraction of global energy use, the energy captured from sources such as wind and solar must be available for consistent use in spite of the daily and seasonal fluctuations in the availability of these resources. Lithium-ion batteries are a promising and prevalent technology for providing this energy storage, but these batteries suffer from degradation modes such as lithium plating and dendrite formation [1] that can shorten the battery’s lifetime and can create significant safety risks, such as battery fires during electric vehicle collisions. The liquid electrolyte in a Li-ion battery contributes significantly to the aforementioned degradation modes, [1] so replacing the liquid with a solid electrolyte can improve both the reliability and safety of energy storage in batteries. Metal-organic frameworks (MOFs) show promise as solid electrolyte materials because of their intrinsic porosity and ion-transport ability. However, the fundamental structure that enables ion transport has not been adequately studied to the extent of being able to optimize the system for ionic conductivity. Here we made progress in understanding how to synthesize and characterize MOFs for potential use in future electrolyte studies. We found that the characterization of the MOF can be impacted by the solvent and additives of synthesis, we learned that the introduction of salt to the MOF for ionic conduction occurs more readily in the absence of water, and we developed a procedure for the growth and characterization of single crystals of MOF-74 for characterization by single-crystal x-ray diffraction (XRD) that allows for full structure solving. These techniques and protocols for MOF characterization that we developed set the stage for a future of MOF solid electrolytes that are designed with their structure-property relationships in mind. Methods for the characterization of MOFs allow for structural information that is integral to their eventual incorporation into batteries as solid electrolytes and their contribution to the energy solution.
Reference:
1. Kyusung Park and John B. Goodenough, Adv. Energy Mater., 2017, 7.
Synthesis of Janus graphene for spatial separation of charges and reduction-oxidation reactions in colloidal photocatalysts [electronic resource]
Keywords: Chemical Engineering.

Photocatalyst particles are attractive for many applications, but electron-hole recombination and surface back-reactions are major problems limiting their efficiency. These problems stem from short separation (~ nanometers) between reduction and oxidation (redox) sites in conventional systems. Here, we show that 2-dimensional Janus particles — Janus graphenes — can be used to spatially separate redox sites by large distances (~ micrometers) on opposite faces of conductive, atomically thin sheets. We used a silicon wafer and a polymer film to successively expose and protect alternate graphene oxide (GO) faces for asymmetric deposition of Pt and TiO2 nanocrystals, thus producing Janus graphene particles (Pt [vertical line] GO [vertical line] TiO2). We used electron microscopy of Janus graphene cross-sections to directly and conclusively show Pt and TiO2 particles on opposite faces of monolayer GO sheets. Spatial separation of redox sites in Pt [vertical line] GO [vertical line] TiO2 — dispersed in liquid — was demonstrated by photoinduced, reductive deposition of Pd onto reduction sites. Although future scale-up of the synthesis is necessary, Janus graphenes could be synthesized with many photocatalytic materials and may provide a general system for spatial separation of redox sites in photocatalyst particles.
Synthetic efficiency through strategic design [electronic resource] : (I) the design and development of novel reactivity regenerating reagents for step economy, (II) the supply-impacting total synthesis of bryostatin 1
Keywords: Chemistry.

Organic synthesis as a discipline is driven at the delivery of high-value molecular entities as research tools, therapeutic agents, reagents, and materials. The simple delivery of these entities, however, does not constitute a successful synthetic effort. Instead, synthetic chemists are in constant pursuit of ideal syntheses that minimize step counts, waste, and development and delivery time; yet maximize chemical yield, safety, and purity and quantity of the resulting outputs. Presented in this defense will be three strategies aimed at this overall goal of efficient synthetic strategies. First, the design and development of 1,2,3-butatriene equivalents will be discussed, including their enabling application to the synthesis of a novel class of staurosporine-inspired kinase inhibitors using a [5+2]/[4+2] tandem cycloaddition sequence. Using a related reactivity regeneration strategy, the second story in this defense demonstrates the scalable synthesis of a new solvatochromic fluorophore enabled by the development of two new tetramethyleneethane equivalents. Finally, a scalable and supply-impacting synthesis of the marine macrolide bryostatin 1, a lead compound for the treatment of Alzheimer's disease and cancer, as well as for the eradication of HIV/AIDS, will be described. This synthesis represents a solution to the supply of bryostatin 1 and related analogs and enables further clinical and academic research on the potential of these transformative PKC modulators. Overall, these three stories serve as a demonstration of how strategic design strategies can contribute to the overall synthetic efficiency and economy of a synthetic sequence.
Synthetic studies toward pactamycin using oxidative alkene and C-H amination technologies [electronic resource]
Keywords: Chemistry.

Selective, oxidative methods for C--N bond formation have been advanced to facilitate a de novo synthesis of pactamycin. A method for the synthesis of 1,2-diamines was developed through a single-step, tandem sequence involving Rh-catalyzed alkene aziridination followed by NaI-promoted rearrangement to an isomeric cyclic sulfamide. Facile ring opening of these products in hot water and pyridine affords differentially protected vicinal diamines. The utility of the method was validated through the preparation of the polyaminoacid-derived natural products, (±)-enduracididine and (±)-allo-enduracididine. A strategy has been delineated toward a synthesis of pactamycin enabled by alkene and C--H amination technologies. Two synthetic routes to the five-membered carbocyclic core of pactamycin were developed, the first utilizing an intramolecular benzoin reaction that enabled access to advanced intermediates for testing the key amination reactions. A second approach proceeded without recourse to protecting groups and makes possible access to enantioenriched material. Efforts to assemble the C1, C2, C3 triamino motif of the cyclopentane core are highlighted by a late-stage Rh-catalyzed chemoselective allylic C--H amination reaction and a Rh-catalyzed intramolecular alkene aziridination. Different approaches for assembling the C1, C2 cis-diamine, including use of the Rh-catalyzed aziridination and subsequent isomerization, are described. In the course of these studies, the core of the C2-epi-pactamycate, which bears all of the requisite nitrogen and oxygen functional groups to the epimeric natural product, was successfully synthesized.
Systematic Study of Promoting Effects in Titania-Based Systems for Hydrogen Production in Photoreforming Reactions
Keywords:  Department of Chemical Engineering
Chemical Engineering
Stanford University
Undergraduate Honors Thesis
Cargnello Lab
photocatalysis
hydrogen production
titanium dioxide
metal oxides
Thesis

There is a pressing need in society to begin to move away from fossil fuels as our main source of
energy due to the production of CO2 caused by their combustion. One promising alternative energy
vector is hydrogen, which burns cleanly in fuel cells, producing only water as a byproduct. Yet,
currently more than 95% of hydrogen is produced through steam reforming fossil fuels in a process
which releases significant amounts of carbon dioxide. A promising alternative to this process is
photoreforming of biomass (i.e. glycerol and glucose) to produce hydrogen and CO2 in a net carbon
neutral cycle which uses only the energy from the sun. TiO2 (titania) is a potential photocatalyst for
this process, but it has issues due to the fast recombination of electron-hole pairs after excitation.
Studies have shown that depositing different metal (i.e. Pd, Pt, Au) nanocrystals on the TiO2 helps
prevent recombination by serving as electron sinks and thus increases catalytic efficiency. In this
study, we used palladium nanocrystals as a co-catalyst with the titania. To further reduce
recombination, we also deposited different metal oxides (MnOx, NiOx, CoOx) to act as hole
collectors and thus promoting agents for the oxidative reaction in order to minimize recombination.
Our results demonstrated a decrease in catalytic activity throughout various deposition techniques
leading us to conclude that the metal oxide co-catalysts were detrimental to catalytic activity at the
concentrations tested (3-10 wt%), possibly due to obstruction of the TiO2’s active surface area.
Tax Responsiveness of the Rich: Revisiting Evidence from Executive Compensation
Keywords:  Department of Economics
executive compensation
elasticity of taxable income
tax policy
Stanford Department of Economics
Thesis

This paper measures the responsiveness of taxable income to changes in the marginal tax rate using panel data on executive compensation since 1992. It exploits variation
from four tax acts: the Omnibus Budget Reconciliation Act of 1993, the Economic
Growth and Tax Relief Reconciliation Act of 2001, the Jobs and Growth Reconciliation Act of 2003, and the American Taxpayer Relief Act of 2012. Stock options have increased significantly as a share of compensation since 1992. I revisit results on the
responsiveness of executives given this trend towards the use of options, and find a
small short-run elasticity for executives, a larger short-run elasticity for CEOs specifically, and no long-run elasticity for either group.
Technological Automation: Past and Present
Keywords: Technological automation
automation
classical antiquity
industrial revolution
robots
machines
artificial intelligence
STS
technology
survey
water wheel
aqueduct
steam engine
machine learning
autonomous vehicles
Thesis

The advancement of mankind is often thought to be linked to developments in science and technology. For thousands of years, we have invented technologies that are meant to make life more efficient. By automating cumbersome tasks, humans can focus their efforts elsewhere and increase their productivity. However, the automated technologies of today - such as robots, robo-advisors (non-human financial advisors based on software algorithms), and customer service bots – are capable of performing operations thought to be out of a science-fiction movie. The number of tasks that a human can carry out that a robot can’t is becoming fewer and fewer each year, putting much of our society at risk of unemployment. This paper examines technological automation through a historical lens, analyzing Classical Antiquity and the British Industrial Revolution in order to have a better understanding of how societies of the past have dealt with waves of automation. How have these episodes been viewed by their respective society? What debates dominated these episodes? And how is the current wave of automation similar to, and different from, these past waves? In addition to the historical analysis, I conducted original research in the form of a survey in order to gather and generalize current public opinion on automation. I find that there is overwhelming support for our current trajectory. John Maynard Keynes warned of technology outpacing human skill, coining the term “technological unemployment.” For him, it was a temporary state in which humans must catch up in order to adapt and learn how to work with these advanced devices. Regardless of whether the current episode is temporary or not, society must have an open conversation about this pressing issue and take steps to mitigate serious negative consequences.
Telomerase expression in the germline cycle [electronic resource]
Keywords: Genetics.

Telomerase inactivation causes loss of the male germline in worms, fish and mice, indicating a conserved dependence on telomere maintenance in this cell lineage. Here, using telomerase reverse transcriptase (Tert) reporter mice, we find that very high telomerase expression is a hallmark of the germline. Telomerase levels in undifferentiated spermatogonia and embryonic stem cells are comparable, and much greater than in somatic progenitor compartments. Within the adult male germline, we uncover an unanticipated gradient of telomerase activity that enables isolation of subpopulation of undifferentiated spermatogonia, the mitotic population where germline stem cells reside, and more mature populations. We exploit this gradient for robust isolation of pure, phenotypically defined subpopulation with the goal of transcriptional and functional analysis. RNA-Seq shows subpopulations of undifferentiated spermatogonia (GFRα1+ and GFRα1- cells) differ principally in receptor tyrosine kinase signaling and cell cycle. We also identify cell surface molecule Melanoma Cell Adhesion Molecule (MCAM) as differentially expressed in these populations. Antibodies to MCAM allow robust isolation of highly enriched populations of GFRα1+ and GFRα1- spermatogonia from adult, wild-type mice without the need to rely on reporter mouse strains. Transplantation into sterile recipients, a proven assay for stem cell activity, shows that both populations demonstrate high transplantation activity and that no germline stem cell activity is found outside the TERTHigh KIT- population. Together, these data provide support for a model for a stem cell pool in which the GFRα1+ and GFRα1- cells make up a heterogeneous stem cell pool and interconvert between these two states based, in part, on access to niche factors. In addition to undifferentiated spermatogonia in adult, the germline expresses high telomerase levels through development and in mature oocytes. We show that primordial germ cells arise from cells expressing high TERT. As development progresses, TERT levels are downregulated with lineage commitment in the soma but remain high in the germline. This pattern to Tert expression is very similar to what is seen for Oct4, an established pluripotency and germline marker.
Temperature compensation of epitaxially encapsulated silicon MEMS resonators [electronic resource]
Keywords: Mechanical Engineering.

Silicon microelectromechanical systems (MEMS) resonator-based timing references have been considered as a promising alternative to quartz crystal resonators. However, due to the intrinsic temperature coefficient of elasticity (TCE) of silicon, most systems exhibit a linear temperature coefficient of frequency (TCf) of -30ppm/℃. This makes temperature compensation essential for high precision timing reference applications, such as timekeeping, inertial measurement or communication. In this thesis, I will present fabrication techniques and various temperature compensation schemes for achieving high temperature stability of silicon MEMS resonators. First, we will discuss two variations of the baseline wafer-level encapsulation (epi-seal) process to allow large lateral transduction gaps and bottom electrodes, respectively. This enables the fabrication of various kinds of high performance resonating MEMS devices that are not available with the baseline process. The second part of this dissertation will focus on two active temperature compensation schemes based on ovenization, which uses Joule heating to operate the resonator at a fixed temperature. Lastly, we will demonstrate the amplitude-frequency effect of anharmonic coupling between two resonant modes, and a novel passive compensation method that utilizes this phenomenon. Interesting nonlinear dynamics behaviors of 1:2 internal resonance will also be presented and discussed.
Templating low dimensional metal organic chalcogenide crystals via diamondoid self-assembly [electronic resource]
Keywords: Materials Science and Engineering.

Low dimensional metal chalcogenides have emerged in the spotlight in recent years and have become principal targets for new material discovery. In my dissertation, I explore a new way to synthesize single crystal metal chalcogenides in low dimensions, by templating their growth using 'diamondoid' self-assembly. Diamondoids are hydrogen-terminated molecular diamonds that share the basic building blocks of bulk diamond. These molecules exhibit unusually strong intermolecular van der Waals interactions. The diamondoids present an unexplored class of 'structure-directing agents' that can be used to direct the synthesis of low dimensional metal chalcogenides, with new structures previously not accessible. Using diamondoids, we have synthesized 1D metal-organic chalcogenide (MOC) single crystals through directed self-assembly. The Copper Adamantylthiolate (1ADCu) MOC crystal shows the smallest copper sulfide nanowire structure with a 3-atom cross-section. We performed density functional theory and molecular dynamics calculations on the 1ADCu MOC crystal, and found that the formation of the copper sulfide nanowire is guided by strong van der Waals attraction between diamondoid ligands, enabling a unique "face-on" growth mechanism for forming extended 1D structures. The same synthetic route can be applied to grow 1D selenium-based MOC crystals. Lastly, we have successfully doped the MOC crystals with different chalcogens, without affecting the overall crystal structure, and demonstrated that these MOC crystals can be optically tuned. Our method to synthesize crystalline metal chalcogenides through diamondoid self-assembly presents a promising route to grow 1D metal chalcogenide structures with tailorable properties. The wide range of low dimensional metal chalcogenide crystals that can be synthesized using diamondoids as structure-directing agents could offer potential candidates in a variety of applications.
Temporal characteristics of intrinsic brain activity based on functional magnetic resonance imaging [electronic resource]
Keywords: Electrical Engineering.

Since its inception in 1992, functional Magnetic Resonance Imaging (fMRI) has become an indispensable tool for studying cognition in both healthy and dysfunctional brains. FMRI monitors changes in the oxygenation of brain tissue resulting from altered metabolism consequent to a task-based evoked neural response, or from spontaneous fluctuations in neural activity in the absence of conscious mentation (the "resting state"). Efforts undertaken in this dissertation focus on how temporal information collected by fMRI can be harnessed and carefully processed to exploit two new directions of resting state functional connectivity: brain network dynamics and high-frequency functional connectivity. The first part of the dissertation presents advancements on a single-time-frame-based methodology that builds upon co-activation pattern analysis, to quantify and synthesize dynamic functional information. With this proposed approach, we reveal elaborate changes exerted by a sustained working memory task compared to resting state, as well as distinct anti-correlation patterns of dorsal and ventral branches of the brain default-mode network. The second part of this dissertation presents first and preliminary explorations into the mechanisms of recently reported high-frequency (> 0.1 Hz) spontaneous neural activity. We show that fractional contributions of non-blood-oxygen-level-dependent components increase as frequency goes up; and that part of existing observations on high-frequency phenomena may stem from improper preprocessing.
Temporal determinants of fungal community assembly [electronic resource]
Keywords: Biological Sciences.

Factors related to the temporal scale of fungal community assembly remain poorly defined. In this dissertation I explore two temporal determinants of fungal community assembly, ecosystem age and species arrival order. First, I explore the effect of ecosystem age using an observational study of the fungi associated with the roots of an ericaceous plant, Vaccinium calycinum, across a 4.1 myr soil chronosequence in Hawaii. I show that soil development promotes greater diversity in ericaceous root-associated fungal communities and that soil-age related nutrient limitation facilitates colonization of ericaceous roots by a greater diversity of non-mycorrhizal fungi in both young and old soils. Second, I use a laboratory microcosm study of root-associated fungi to show that fungal species pools from older ecosystems include species that are more likely to coexist within the roots of a single seedling. Finally, I use a community of wood-decomposing fungi in a microcosm experiment to show that the interactive effects of top-down (grazing) and bottom-up (nutrient availability) forces determine the importance of immigration history (i.e., priority effects) for community composition and function. Taken together these results demonstrate that temporal processes occurring at both short and long time scales can be important determinants of fungal community assembly.
Territorial Disputes in Court: Power, Compliance, and Defiance
Keywords:  Center for International Security and Cooperation
Center for International Security and Cooperation
territorial disputes
international courts
great powers
South China Sea
Bakassi Peninsula
Chamizal
Thesis

This thesis focuses on the conditions under which powerful states comply with adverse international court rulings on interstate territorial disputes. On July 12, 2016, the Permanent Court of Arbitration (PCA) at The Hague ruled on Philippines v. China with respect to the legality of China’s claims and activities in the South China Sea. The arbitration court decisively ruled in favor of the Philippines, though China vowed to reject and not comply with the arbitral ruling. Although realist theory suggests that international courts are ineffective, this thesis finds reason for cautious optimism concerning Chinese compliance with the arbitration court ruling in the long term. Powerful states primarily comply with adverse international court rulings on territorial disputes out of convenience and to improve their reputation. In addition, domestic politics can either facilitate or hinder compliance. This thesis analyzes the Chamizal dispute between the United States and Mexico as well as the Bakassi Peninsula dispute between Nigeria and Cameroon. Furthermore, great powers rarely seek out international legal dispute mechanisms and are usually able to screen out cases that might result in adverse outcomes. Those cases that make it to court involve peripheral territories. By showing how powerful states have historically responded to international court cases on territorial disputes, this thesis examines the prospect of China complying with Philippines v. China and how this affects the longstanding disputes in the South China Sea.