VictorJuiz/thesis huggingface dataset:
Stuck in the Matrix- Patch Matrix Dynamics in Florida Scrub
Keywords:  Department of Biology
Forest ecology
Ecology
Plant ecology
Biogeography
Florida
Scrub
Rare plants > Ecology
Rare plants > Geographical distribution
Rosemary Scrub
Text
Thesis

Humans are fragmenting habitat and changing natural disturbance regimes at an unprecedented rate. Patch dynamics addresses how smaller patches of enclosed habitat interact with their surroundings, the matrix. Patches have been studied extensively in forested ecosystems where treefall or limb fall gaps are short-lived and stochastic, but patches also occur in grasslands and scrublands across the world. Although the relationship between patch characteristics such as size or degree of isolation have been studied, exactly how patch species interact with the surrounding habitat in non-forested systems is poorly understood. This study aims to specifically examine if and how plant species cover and plant species diversity in patches of Florida rosemary scrub are affected by the matrix spatial structure (i.e., bare sand cover) and the shrub cover in the surrounding shrub matrix. Despite a similarity in dominant shrubs and shrub species cover, I found that neither the shrub cover in the matrix nor matrix structure had any significant effect on the species cover or species diversity in the patches. However, a significant effect was found between matrix shrub cover and patch species cover when factoring in degree of isolation from other patches. This suggests that patches may interact more with each other than they do with the matrix when considering matrix spatial structure and composition. This could be a result of the high number of patch specialists in this system. Future studies of the scrub could investigate specific species interactions or spatial distributions of ecologically contrasting species. Future studies could also investigate whether species cover in rosemary scrub patches may follow island biogeography theory or some other metapopulation model less dependent on patch-matrix effects. Conservation of Florida rosemary scrub should emphasize reducing habitat loss for what may be already insular patches.
Studies of hydrogels and concentrated aqueous ionic solutions by optical Kerr effect
Keywords: Humanities and Sciences.
Chemistry.

A comprehensive understanding of water and its properties is vital for many Earth processes, ranging from the vast scales of climate and geology to the molecular impact on life. It is essential to have a deep knowledge of water to address critical issues such as climate change, energy, and medicine. This research is specifically focused on two main questions: how water impacts polymer structure and how salt affects water properties. All the data were collected using optical heterodyne-detected optical Kerr effect (OHD-OKE). The ultrafast dynamics of acrylamide monomers (AAm), polyacrylamide (PAAm), and polyacrylamide hydrogels (PAAm-HG) in water were investigated using OHD-OKE. In this study, the systems' dynamics slowed with increasing concentration. AAm samples exhibited tetra-exponential decays, mostly following Debye-Stokes-Einstein behavior except at the highest concentration. Low PAAm concentrations displayed a single power law decay, while high PAAm concentrations and all PAAm-HG concentrations exhibited two power laws. PAAm and PAAm-HG displayed nearly identical dynamics at high concentrations, indicating similar chain-chain interactions. The dynamics of concentrated lithium chloride and lithium bromide aqueous solutions were studied at moderate to high concentrations. While pure water decayed biexponentially, LiCl/LiBr-water decays were tetra-exponential at all concentrations. The faster two decays originated from water dynamics, while the slower two decays reflected ion-water network dynamics. The fastest decay was the same as pure water at all concentrations. The second decay matched pure water at lower concentrations but slowed with increasing concentration. The slower dynamic, the third- and fourth-time constants, arose from ion-water complexes and an extended ion-water network at the highest concentrations. Comparisons with simulations enabled the assignment of dynamics to specific ion-water structures. The concentration-dependent bulk viscosity and ion-water network dynamics were directly correlated, providing an atomistic-level understanding of viscosity
Studies on the photochemical [2+2] cycloadditions of unactivated olefins
Keywords: Humanities and Sciences.
Chemistry.

[2+2] cycloadditions are arguably the most powerful reactions for constructing cyclobutanes which are prominent motifs in natural products and are becoming increasingly common pharmacophores in medicinal chemistry. Despite the growing number of [2+2] methodologies, virtually all of them rely on the cyclization of at least one activated π partner. An exception to this rule is the Kochi-Salomon reaction, which is able to cyclize aliphatic olefins in the presence of simple Cu(I) catalysts. Introduced over 50 years ago, it has seen very little in the way of methodological development and still suffers from a number of drawbacks including the need for moisture- and air-sensitive reagents, a limited substrate scope and a lack of stereocontrol. This thesis describes strategies to address these shortcomings starting with our efforts at rendering the Kochi-Salomon reaction enantioselective, first using weakly coordinating chiral counterions and then using chiral diene ligands. Although ultimately unsuccessful, these attempts provided valuable insight into Cu-catalyzed [2+2] photocycloadditions which led to the development of aqueous amine-tolerant cyclizations of unactivated olefins. Basic amines, hitherto incompatible in these types of reactions, may be protonated then cyclized in water, an unlikely solvent, using some of the most standard reagents available in any chemistry lab. This discussion is followed by a series of smaller ventures into further developments of the Kochi-Salomon reaction, including strategies to exert diastereocontrol and efforts to cyclize sulfur-containing substrates and quaternary ammonium substrates. The final chapter details the development of a scalable route to anti-[3]-ladderdiene. While not related to the Kochi-Salomon reaction, this strained molecule fits well into the realm of cyclobutanes which is central to this thesis
A study of two-dimensional superconductors with scanning-SQUID microscopy
Keywords: Humanities and Sciences.
Physics.

Superconductors, with characteristic zero-resistance, Messier screening, and phase coherence at low temperatures, find applications in power transmission, high-speed transportation, and quantum computing. The warmest ambient pressure superconductor to date has a transition temperature of 100 Celsius below room temperature. Finding room-temperature superconductors is the holy grail. In order to achieve that, it is necessary to understand the superconducting mechanism through careful characterization of existing superconductors. In recent years, we have witnessed the discovery of several new superconducting systems. The infinite-layer nickelate, a structural analogy of the famous cuprates, was achieved through topotactic reduction. The twisted few-layer graphene systems displayed complex phase diagrams similar to the cuprates. The monolayer transition-metal dichalcogenide showed evidence of topological superconductivity. In addition, straining well-established high-temperature superconductors such as cuprates was found to enhance the critical temperature. The ever-so-vibrant research on superconductivity opens new possibilities for deciphering the mechanism of these strongly correlated electron systems. This thesis presents scanning SQUID microscopy (SSM) imaging of the above-mentioned superconductors. The SSM visualizes mesoscopic magnetic structures that cannot be seen in transport measurements. Our results break assumptions that might be used to extrapolate useful physical quantities in bulk measurements. Applying a local field, the SSM directly probes the local superfluid density, revealing spatial inhomogeneity and its interplay with intrinsic magnetic structures, namely vortices.
A study on the current state and success factors of construction technology startups
Keywords: Engineering.

Construction technology startups have struggled to perform as well as their counterparts in other industries, and the reasons behind this discrepancy remain largely unknown. Existing research has focused on general factors influencing success but has overlooked the specific context of construction technology companies. This gap is filled by investigating the construction tech landscape, identifying unique characteristics, and examining the factors that influence their success. Through the CIFE horseshoe method, which emphasizes a holistic understanding of construction projects, and a quantitative-leaning mixed method approach, two datasets were analyzed; one focused on construction technology startups and the other on general technology startups. These datasets were sourced from investment intelligence platforms like Crunchbase and PitchBook. Through exploratory data analysis, including distributions, and confirmatory analysis utilizing the Mann-Whitney U test and logistic regression, this thesis unveils the distinct characteristics of construction startups and identifies the parameters that contribute to their success. The findings highlight that construction technology startups exhibit uniqueness in terms of their founding team composition, fundraising strategies, and exit events. Founding teams typically consist of two-person teams with technical backgrounds, emphasizing agility and collaboration. Funding dynamics reveal shorter durations for early-stage funding and longer durations for late-stage funding. Successful exits are more commonly achieved through mergers and acquisitions. Construction tech startups exhibit unique characteristics, such as larger founding teams and a prevalent optimum exit period between 6-8 years. Factors influencing success include waiting to raise the first funding round, having architecture, engineering, and construction (AEC) experience within the team, and targeting various customer segments. Startups focused on construction management, design/engineering, and data management/analytics show higher success rates. These insights inform strategic decision-making and offer opportunities for further research and exploration in the construction technology startup landscape. A notable contribution of this thesis is the in-depth exploration of construction-focused technology companies, delving into unconventional variables such as experience in AEC, as well as customer base analysis. By considering these factors, a more comprehensive understanding of the construction tech landscape is obtained, shedding light on the industry-specific challenges and opportunities
A study on the extended bogomolny equations
Keywords: Humanities and Sciences.
Mathematics.

This thesis contains results on the analysis and geometry of the extended Bogomolny family of equations (EBF). The first result of this thesis is a proof of the existence of model knot solutions for any member of the above family. The second result is the construction and partial classification of solutions to the EBF at =1$ under the assumption that the Higgs field is either nilpotent or semisimple and constant. The last result of this thesis gives a description of the moduli structure of the solution space of EBF at =1$ when the underlying space is a closed Riemann surface times the half line in terms of the moduli space of Higgs bundles
Surface water-groundwater interactions during extreme floods : hydrologic and biogeochemical controls on water quality
Keywords: Sustainability.
Earth System Science.

In both natural and human-impacted ecosystems, floods play a pivotal role in shaping our environment. In natural systems, floods replenish groundwater and support riparian habitats. In intensively managed environments, engineered floods have become a valuable tool for mitigating the effects of global change. During flood managed aquifer recharge (flood-MAR), for example, water managers intentionally inundate working landscapes in order to replenish depleted aquifers. Both natural and engineered floods deliver an influx of water and reactive species into the subsurface, triggering a complex web of hydrologic and biogeochemical processes that can mobilize nutrients and contaminants, impacting water quality. Through a combination of modeling and data science approaches, my research sifts through this complexity and seeks to understand the fundamental drivers of surface and groundwater quality during extreme floods. In my first chapter, I examine the impact of seasonal floods on redox cycling in heterogeneous floodplain aquifers. Through stochastic reactive transport simulations, I show that the hydrogeologic properties of a floodplain often exert a stronger control on redox conditions than do biogeochemical reaction rates. In subsequent chapters, I identify controls on the movement of water and solutes through the subsurface during flood-MAR. Using high-resolution hydrogeophysical data and hydrologic simulations, I find that tension-driven flow within the vadose zone draws recharge water away from coarse-grained flow paths and traps it in lenses of fine-grained sediment. These fine-grained sediments can take years to drain following inundation, limiting recharge efficiency. In my final chapter, I pair hydrologic simulations with Lagrangian particle tracking to investigate contaminant transport during flood-MAR. Results reveal that recharge water applied at the surface takes decades to reach the water table, during which time some contaminants may be removed through biogeochemical reactions. Overall, my work deepens our understanding of subsurface hydrologic and biogeochemical processes during inundation and provides actionable insights for sustainable water resource management in a changing climate.
Survival after Hospital Admission in Adults with Liver Cirrhosis in California
Keywords: Proportional hazards models
Liver cirrhosis- survival
Text
Thesis

Cirrhosis of the liver currently ranks 9th amongst all causes of death in the United States, with a prevalence of 0.27%. In the world, with a prevalence of about 1.4%, it caused around 1.32 million or 2.4% of the total deaths in 2017. Cirrhosis is characterized by widespread fibrosis and regeneration of liver tissue, which is in response to irreversible and usually prolonged damage to the liver. The continued presence of the inciting factor causes progression to end-stage liver disease with or without hepatocellular carcinoma or liver cancer. The commonest cause in the US is chronic viral hepatitis by Hepatitis C or Hepatitis B virus, while alcohol-associated liver disease is more common worldwide. Currently, cirrhosis due to hepatitis is on a downward trend because of newer, more effective therapeutic options, whereas a lifestyle disorder called non-alcoholic fatty liver disease, as a cause of cirrhosis, is on the rise.
Survival with compensated liver cirrhosis is estimated to be around 12 years, while it is only 2 years with the decompensated form of the disease. There has not been any major population-based study in the United States providing us with recent survival estimates. Hence, to obtain current estimates, we used the Health Care Access and Information (HCAI) Patient Discharge Database of the Government of California to obtain a cohort of all California adults with diagnosed liver cirrhosis from 2005 to 2013. This database is linked to the California Comprehensive Master Death File via a unique Record Linkage Number, which allowed us to perform a time-to-death analysis. Using Kaplan-Meier methods, we estimated the median survival time for the sample overall, and stratified by variables like age, sex, race, ethnicity, payment type, and decompensation status. We used Cox proportional hazards regression to estimate hazard ratios for the outcome of death.
Our sample size consisted of 193,127 adults with an average age of 59.4 and a standard deviation of 13.1 years. 63.5% of our sample was male, 70.2% were white, and 30.7% were of Hispanic ethnicity. 39.3% were decompensated at baseline, and 39.1% of the sample used Medicare to pay for the services received. The median survival time for the overall sample was 4.16 (95% CI 4.09-4.24) years, with age more than 68 years and decompensated disease increasing the risk of death by 99% (95% CI 95%-104%) and 53% (95% CI 51%-55%), respectively. Belonging to the Asian race decreased the risk by 7% (95% CI 5%-10%), and the female sex had a 14% (95% CI 13%-16%) lower risk. The median survival for compensated liver disease was 5.37 (95% CI 5.25-5.48) years while it was 2.77 (95% CI 2.71-2.83) years for those decompensated at baseline.
Synthesis and applications of flower-like polyacrylonitrile (PAN) and PAN-derived carbon superstructures
Keywords: Engineering.
Chemical Engineering.

Polyacrylonitrile (PAN) and PAN-derived carbon materials have diverse applications in areas such as adsorption, separation, energy storage, and biomedical applications. However, synthesizing nanostructured PAN is challenging, often requiring complex, multi-step processes like sacrificial templating. Recently, researchers have reported a simple, one-pot free radical polymerization method for synthesizing flower-like PAN superstructures. This method has drawn increasing interest in recent years due to the unique morphology of the resulting structures. The flower-like shape of the PAN superstructures offers many benefits, including open-pore structures that are well suited for applications such as sensors, separation, catalysis, and energy storage. Additionally, the simple synthesis procedure allows for scalability in industrial production, making it easier to produce large quantities of nanostructured PAN. However, the formation process for the complex flower-like structures in the one-step polymerization reaction remains unclear, and the advantages of the flower-like morphology are still under-explored. This thesis aims to contribute to our understanding of the flower-like PAN superstructures and their potential uses in various fields. The thesis consists of four main parts. The first part provides a comprehensive review summarizing recent progress in developing similar flower-like superstructures, including their synthesis, formation mechanism, and existing applications. The second part focuses on investigating the formation mechanism of flower-like PAN particles using various in situ and ex situ characterization techniques, such as in-situ ultra-small-angle x-ray scattering (USAXS). The third part of the thesis focuses on fine-tuning and developing more advanced PAN and PAN-derived carbon superstructures. This includes tuning and designing sub-particle level, particle level, and device-level superstructures. The fourth part of the thesis focuses on demonstrating the potential of flower-like PAN and PAN-derived carbon particles (carbon flower) in various applications, including lithium metal anodes, sulfur cathodes, supercapacitors, and flexible pressure sensors. This thesis provides a fundamental understanding of the formation mechanism of flower-like PAN superstructures and demonstrates their advantages in a range of applications
Synthesis and evaluation of novel tiglianes for PKC-related therapeutic indications
Keywords: Humanities and Sciences.
Chemistry.

EBC-46 (aka tigilanol tiglate), has emerged as an exciting anti-cancer agent for the treatment of solid tumors. Intratumoral injection leads to activation of its primary target protein kinase C (PKC), causing increased permeability of tumor endothelial cells and subsequent inflammation to lead to tumor death. Currently, EBC-46 is obtained via extraction of blushwood tree berries, a potentially unsustainable supply tree found only in Queensland, Australia. To ensure a sustainable supply and enable further research into EBC-46, my research has focused on the development of a semi-synthesis of EBC-46 from phorbol, an abundantly available starting material. This work was since been published in Nature Chemistry and a patent has been filed. To obtain phorbol, Croton tiglium seeds are subjected to a robust extraction process that affords upwards of 10 grams of phorbol from 3 kg of seeds. With phorbol in hand, the molecule is walked though a unique oxidation sequence that yields EBC-46 in 12 % overall yield and 12 steps (> 2 grams synthesized). With a sustainable supply of EBC-46, several analogs have been synthesized to probe its structure-activity relationship with PKC. Ongoing efforts continue to elucidate how structural changes to EBC-46 influence its PKC isoform selectivity, potency, and therapeutic potential
Synthesis, evaluation, and mechanistic analysis of ruthenium(II) precatalysts for C-H hydroxylation
Keywords: Humanities and Sciences.
Chemistry.

Current efforts to improve C--H oxidation methodologies are constrained by the limited set of structurally flexible metal-ligand complexes capable of effecting such transformations. We describe the development of a synthetic route towards novel heteroleptic Ru(II) complexes bound to both a 2,2'-bipyridine ligand and a strong σ-donating bidentate group. The selective and convenient synthesis of these complexes is possible under mild conditions that promote Ru- cymene ligand substitution. Evaluation of these heteroleptic complexes as precatalysts for C--H oxidation resulted in the discovery of an efficient precatalyst that displays excellent stability and turnover numbers. In efforts to further develop this technology, mechanistic studies to identify catalyst speciation and decomposition pathways were undertaken. A combination of reaction kinetics analysis, isotopic labeling, mass spectrometry, and electrochemical measurements have revealed that ligand oxidation is critical for generating an active catalyst, and highlight reactivity and stability differences between homo- and heteroleptic Ru complexes. Insights gained from these studies should inform development of next-generation C--H oxidation catalysts.