Physical Sciences and Mathematics Commons^™

The Dynamic Relationship Between Permafrost And Landcover In Northwestern Canada’S Discontinuous Permafrost Zone, Olivia Carpino

Theses and Dissertations (Comprehensive)

Northwestern Canada’s subarctic is among the most impacted regions in the world as it is experiencing rapid climatic and environmental change. As a result, northwestern Canada has been experiencing region-wide permafrost thaw and disappearance, both of which are also occurring at unprecedented rates. Permafrost temperatures in the Taiga Plains have been warming steadily over the last several decades, which has been particularly detrimental across its lower latitudes of the discontinuous permafrost zone where the permafrost is already relatively thin and warm. These factors indicate that permafrost in the southern Taiga Plains may be in a state of disequilibrium with the …

Contrasting Seasonal Cycling Of Arsenic In A Series Of Subarctic Shield Lakes With Different Morphometric Properties, Jeremy Harbinson

Theses and Dissertations (Comprehensive)

The subarctic shield near Yellowknife, Northwest Territories (NWT), is populated with thousands of small lakes (<1.5 km²) and several large lakes. Historic mining activities in the region have left a legacy of environmental impacts and widespread arsenic (As) contamination in both aquatic and terrestrial environments. In particular, several small subarctic lakes near Yellowknife have been previously documented to be contaminated with high levels of As. Subarctic lakes are characterized by seasonal ice-cover that can persist for more than half of the year, yet little is known about the under-ice spatial and seasonal dynamics of As cycling. The objective of …

Controls On Thermokarst Lake Water Balances In The Inuvik - Tuktoyaktuk Region, Evan J. Wilcox

Theses and Dissertations (Comprehensive)

There are tens of thousands of thermokarst lakes in the Inuvik-Tuktoyaktuk region, located in the northwest corner of the Northwest Territories, Canada. These lakes formed following the last glacial period in areas where ice-rich permafrost thawed and created depressions in the landscape. The Inuvik-Tuktoyaktuk region is one of the fastest warming regions in the world, leading to changing precipitation patterns, permafrost thaw and deciduous shrub expansion, all of which are affecting the water balance of thermokarst lakes. During the past several decades, lake expansion and contraction have been observed in response to fluctuations in precipitation. While these changes in lake …

Dynamical Aspects In (4+1)-Body Problems, Ryan Gauthier

Theses and Dissertations (Comprehensive)

The n-body problem models a system of n-point masses that attract each other via some binary interaction. The (n + 1)-body problem assumes that one of the masses is located at the origin of the coordinate system. For example, an (n+1)-body problem is an ideal model for Saturn, seen as the central mass, and one of its outer rings. A relative equilibrium (RE) is a special solution of the (n+1)-body problem where the non-central bodies rotate rigidly about the centre of mass. In rotating coordinates, these solutions become equilibria.

In this thesis we study dynamical aspects of planar (4 + …

Mechanistic Studies Of Co2 Electrochemical Reduction (Co2er) On Cu And Cuo Nanoparticles With In-Situ Atr-Ftir Spectroscopy, Jason Hsu

Theses and Dissertations (Comprehensive)

Global climate change is a major challenge facing the world in the 21st century. This environmental crisis originated from excess amounts of atmospheric carbon dioxide (CO2) released from burning fossil fuels. One promising remediation method to decrease atmospheric CO2 levels is called carbon dioxide electrochemical reduction (CO2ER). In CO2ER, the CO2 gas undergoes chemical reduction to other hydrocarbon fuels. For CO2ER to take place, an energy source and a catalyst are needed. In this thesis, three aspects of CO2ER were investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy coupled with other surface sensitive characterization tools. First, we studied …

Opposite Trees, Theo Goossens

Theses and Dissertations (Comprehensive)

A spanning tree of a graph G is a connected acyclic subgraph of G that includes all of the vertices in G. The degree of a vertex is the number of edges incident to that vertex. Given a spanning tree T of a graph G, an opposite tree of T is a spanning tree of G where the degree of each of its vertices is different from its degree in T. For complete, complete bipartite, and complete multipartite graphs, we give the conditions spanning trees of these graphs must satisfy in order to have an opposite tree.

Properties Of (Claw, 4k₁, Bridge)-Free Graphs, Taite Lagrange

Theses and Dissertations (Comprehensive)

Given a set H of graphs, a graph G is H-free if it does not contain any graph in H as an induced subgraph. The complexity of the colouring problem is known when H is a set of graphs on four vertices, with three exceptions. One of those exceptions is the case of {claw, 4K₁}-free graphs, for which our classes of {claw, 4K₁, bridge}-free and {claw, 4K₁, bridge,C₄-twin}-free graphs are subclasses.

The original goal of this work was to prove that {claw, 4K₁, …

The Design And Characterization Of Gold Nanoclusters As Elementary Building Blocks, Heather Gaebler

Theses and Dissertations (Comprehensive)

Gold nanoclusters with diameters in the quantum size regime (< ~2 nm) are promising building blocks for the design of novel nanomaterials as they exhibit unique size-dependent properties that can be altered and fine-tuned. The research outlined in this PhD thesis employs density functional theory to construct and analyze small ligand-protected cage and rod-shaped nanoclusters. Chapter 2 reports stable halide-protected gold nanocages that were engineered to have a closed-shell valence electron count of 18. This study finds that nanocages comprised of 19 and 20 gold atoms can be converted into stable magic number species containing 18 valence electrons by modifying their charged states via adsorption of halide ligands to the cage’s surface. Chapter 3 reports stable ligand-protected gold nanoclusters with a tetrahedral Au₄ core that were engineered to have a closed-shell valence electron count of 2. This study investigates the structural and electronic effects of halide and alkoxy ligands on the tetrahedral nanocluster and concludes that the results support the broader conclusion that it’s possible to fine-tune the stability and electronic properties of small gold nanoclusters using appropriate ligands. Chapter 4 reports stable gold nanorods that have diameters in the quantum regime that were constructed from elementary building blocks that contain “halide-staples”. This study presents different orientations of the “halide-staple” motifs on …

Distributed Spatial Data Sharing: A New Era In Sharing Spatial Data, Majid Hojati

Theses and Dissertations (Comprehensive)

The advancements in information and communications technology, including the widespread adoption of GPS-based sensors, improvements in computational data processing, and satellite imagery, have resulted in new data sources, stakeholders, and methods of producing, using, and sharing spatial data. Daily, vast amounts of data are produced by individuals interacting with digital content and through automated and semi-automated sensors deployed across the environment. A growing portion of this information contains geographic information directly or indirectly embedded within it. The widespread use of automated smart sensors and an increased variety of georeferenced media resulted in new individual data collectors. This raises a new …

Nitrogen: Both A Potential Stimulator And Suppressor Of Cyanobacterial Blooms In Temperate Lakes, Catherine Goltz

Theses and Dissertations (Comprehensive)

Cyanobacterial blooms are complex phenomenon that are impacted and controlled by various factors such as lake depth, air temperature, wind, and nutrient loading. Nutrients such as phosphorus, nitrogen and iron all have very differing effects on cyanobacterial blooms. While phosphorus and iron are known to drive cyanobacterial biomass, nitrogen has been observed to have a direct impact on toxin synthesis. Nitrogen exists in the environment in many different forms such as atmospheric N₂, in inorganic forms such as nitrate and ammonium as well as in organic forms such as urea which can all affect cyanobacterial bloom development differently. …

A Machine Learning Approach To Classify Open Water And Ice Cover On Slave River Delta, Ida Moalemi

Theses and Dissertations (Comprehensive)

Seasonal temperature trend and ice phenology in Great Slave lake (GSL), are strongly influenced by warmer inflow from Slave river. The Slave river flows to GSL through Slave river delta (SRD), bringing a rise in temperature that triggers the ice break-up process of the lake. Slave river discharge is subject to multiple stressors including climate warming and upstream water activities, which in turn, directly affects the GSL break-up process. Consequently, monitoring the break-up process at SRD, where the river connects to the lake, serves as an indicator to better understand the cascading effects on GSL ice break-up. This research aims …

Phosphorus Release And Recovery From Simulated Ferric Wastewater Sludge, Aseel Alnimer

Theses and Dissertations (Comprehensive)

Phosphorus (P) is a fundamental element necessary for all life forms and a key component in the fertilizer industry. Meanwhile, the excessive load of P to water bodies due to human activities has the potential to promote eutrophication. Wastewater treatment plants remove P either biologically or chemically and produce P rich sludge which could be a potential renewable source for P. At present, commercial technologies exist for P recovery from biological wastewater sludge. However, P recovery from chemical sludge particularly iron(III)-phosphate (Fe-P) sludge generated in chemical P removal plants that use iron(III) salts remains a challenge.

This study explored, in …

Borsuk–Ulam Type Theorems For G-Spaces With Applications To Tucker Type Lemmas, Oleg R. Musin, Alexey Yu. Volovikov

School of Mathematical & Statistical Sciences Faculty Publications

In this paper we consider several generalizations of the Borsuk–Ulam theorem for G-spaces and apply these results to Tucker type lemmas for G-simplicial complexes and PL-manifolds.

Equity In Focus : Investigating Gender Disparities In Glioblastoma Via Propensity Score Matching, Solomon Eshun

School of Mathematical & Statistical Sciences Faculty Publications

Gender disparities in health outcomes have garnered significant attention, prompting investigations into their underlying causes. Glioblastoma (GBM), a devastating and highly aggressive form of brain tumor, serves as a case for such inquiries. Despite the mounting evidence on gender disparities in GBM outcomes, investigations specific at the molecular level remain scarce and often limited by confounding biases in observational studies. In this study, I aimed to investigate the gender-related differences in GBM outcomes using propensity score matching (PSM) to control for potential confounding variables. The data used was accessed from the Cancer Genome Atlas (TCGA), encompassing factors such as gender, …

Deriving Spatially Explicit Direct And Indirect Interaction Networks From Animal Movement Data, Anni Yang, Mark Q. Wilber, Kezia R. Manlove, Ryan S. Miller, Raoul Boughton, James Beasley, Joseph Northrup, Kurt C. Vercauteren, George Wittemyer, Kim Pepin

United States Department of Agriculture Wildlife Services: Staff Publications

Quantifying spatiotemporally explicit interactions within animal populations facilitates the understanding of social structure and its relationship with ecological processes. Data from animal tracking technologies (Global Positioning Systems [“GPS”]) can circumvent longstanding challenges in the estimation of spatiotemporally explicit interactions, but the discrete nature and coarse temporal resolution of data mean that ephemeral interactions that occur between consecutive GPS locations go undetected. Here, we developed a method to quantify individual and spatial patterns of interaction using continuous-time movement models (CTMMs) fit to GPS tracking data. We first applied CTMMs to infer the full movement trajectories at an arbitrarily fine temporal scale …

High Winds And Melting Sea Ice Trigger Landward Movement In A Polar Bear Population Of Concern, Annie Kellner, Todd C. Atwood, David C. Douglas, Stewart W. Breck, Colorado State University - Fort Collins

United States Department of Agriculture Wildlife Services: Staff Publications

Some animal species are responding to climate change by altering the timing of events like mating and migration. Such behavioral plasticity can be adaptive, but it is not always. Polar bears (Ursus maritimus) from the southern Beaufort Sea subpopulation have mostly remained on ice year-round, but as the climate warms and summer sea ice declines, a growing proportion of the subpopulation is summering ashore. The triggers of this novel behavior are not well understood. Our study uses a parametric time-to-event model to test whether biological and/or time-varying environmental variables thought to influence polar bear movement and habitat selection …

Evaluation Of The Effect Of Hydrated Lime On The Scavenging Of Feral Swine (Sus Scrofa) Carcasses And Implications For Managing Carcass-Based Transmission Of African Swine Fever Virus, Courtney F. Bowden, James Grinolds, Gregory Franckowiak, Loma Mccallister, Joe M. Halseth, Matthew Cleland, Travis Guerrant, Michael J. Bodenchuk, Robert Miknis, Michael C. Marlow, Vienna R. Brown

United States Department of Agriculture Wildlife Services: Staff Publications

African swine fever (ASF) is a devastating hemorrhagic disease marked by extensive morbidity and mortality in infected swine. The recent global movement of African swine fever virus (ASFV) in domestic and wild swine (Sus scrofa) populations has initiated preparedness and response planning activities within many ASF-free countries. Within the US, feral swine are of utmost concern because they are susceptible to infection, are wide-spread, and are known to interact with domestic swine populations. African swine fever virus is particularly hardy and can remain viable in contaminated carcasses for weeks to months; therefore, carcass-based transmission plays an important role in the …

Disease Progression And Serological Assay Performance In Heritage Breed Pigs Following Brucella Suis Experimental Challenge As A Model For Naturally Infected Feral Swine, Vienna R. Brown, Ryan S. Miller, Courtney F. Bowden, Timothy J. Smyser, Nicholas A. Ledesma, Aim E. Hartwig, Paul Gordy, Aaron M. Anderson, Stephanie M. Porter, Kate Alexander, Zane Gouker, Tom Gidlewski, Richard A. Bowen, Angela M. Bosco-Lauth

United States Department of Agriculture Wildlife Services: Staff Publications

Invasive feral swine (Sus scrofa) are one of the most important wildlife species for disease surveillance in the United States, serving as a reservoir for various diseases of concern for the health of humans and domestic animals. Brucella suis, the causative agent of swine brucellosis, is one such pathogen carried and transmitted by feral swine. Serology assays are the preferred field diagnostic for B. suis infection, as whole blood can be readily collected and antibodies are highly stable. However, serological assays frequently have lower sensitivity and specificity, and few studies have validated serological assays for B. suis in feral swine. …

Validation Of A Nutria (Myocastor Coypus) Environmental Dna Assay Highlights Considerations For Sampling Methodology, Anna M. Mangan, John A. Kronenberger, Ian H. Plummer

United States Department of Agriculture Wildlife Services: Staff Publications

Nutria (Myocastor coypus) is a semiaquatic rodent species that is invasive across multiple regions within the United States. Here, we evaluated a qPCR assay previously described for use in Japan for application across invasive populations in the United States. We also compared two environmental DNA sampling methodologies for this assay: field filtration of large volumes of water passed through filters versus direct sampling of small volumes of water. We validated assay specificity, generality, and sensitivity, compared assay performance between two independent laboratories, and successfully tested the assay in situ on a known wild population. The filtration method required …

Perturbations Highlight Importance Of Social History In Parakeet Rank Dynamics, Annemarie Van Der Marel, Xavier Francis, Claire L. O'Connell, Cesar O. Estien, Chelsea Carminito, Virginia Darby Moore, Nickolas Lormand, Bryan M. Kluever, Elizabeth A. Hobson

United States Department of Agriculture Wildlife Services: Staff Publications

Dominance hierarchies can provide many benefits to individuals, such as access to resources or mates, depending on their ranks. In some species, rank can emerge as a product of a group’s history of social interactions. However, it can be difficult to determine whether social history is critical to rank in observation-based studies. Here, we investigated rank dynamics in three captive groups of monk parakeets (Myiopsitta monachus). We used experimental social perturbations to test whether social history shapes rank emergence in these groups. Using targeted removals and reintroductions, we tested whether differently ranked individuals could re-take their ranks in hierarchies after …

การเปรียบเทียบการทำนายทิศทางของราคาหุ้นไทยโดยใช้ตัวแบบ Random Forests, Xgboost และ Lightgbm, สาธิตา ไชยมหา

Chulalongkorn University Theses and Dissertations (Chula ETD)

การศึกษานี้มีวัตถุประสงค์เพื่อทำนายทิศทางของหุ้นไทย โดยทำการทดลองเปรียบเทียบเครื่องมือทางสถิติด้วยตัวแบบ Random Forests, XGBoost และ LightGBM โดยใช้ตัวแปรค่าของข้อมูลก่อนหน้า (Lag Features) เพียงอย่างเดียว ข้อมูลตัวชี้วัด (Indicators) ของหุ้นเพียงอย่างเดียว และ ข้อมูลตัวชี้วัด (Indicators) ของหุ้นร่วมกับข้อมูลก่อนหน้า (Lag Features) กับทั้ง 3 ตัวแบบ ด้วยวิธีการปรับแต่งไฮเปอร์พารามิเตอร์ระหว่างการปรับให้เหมาะสมแบบเบย์ (Bayesian Search) และการค้นหาแบบสุ่ม (Random Search) ในการทำนายทิศทางหุ้นล่วงหน้า 1, 3, 5,10, 15, 30, 60, 90 และ 180 วัน โดยศึกษาหุ้นทั้งหมด 8 ตัวที่ต่างอุตสาหกรรม ดังนี้ เกษตรและอุตสาหกรรมอาหาร (AGRO) สินค้าอุปโภคบริโภค (CONSUMP) ธุรกิจการเงิน (FINCIAL) สินค้าอุตสาหกรรม (INDUS) อสังหาริมทรัพย์และก่อสร้าง (PROPCON) ทรัพยากร (RESOURC) บริการ (SERVICE) เทคโนโลยี (TECH) ข้อมูลราคาหุ้นจาก finance.yahoo.com ปี ค.ศ. 2014-2023 โดยเลือกหุ้นที่มีมูลค่าสูงสุดจากแต่ละกลุ่มอุตสาหกรรม ซึ่งขั้นตอนการแบ่งข้อมูลออกเป็นข้อมูลชุดฝึกฝน (Training Set) และข้อมูลชุดทดสอบ (Test Set) และทำการแบ่ง K-Fold Cross-Validation ทั้งหมด 5 Fold และวัดผลตัวแบบด้วยค่าความแม่นยำ (Accuracy), Precision, Recall, F1-Score และ AUC จากการศึกษาพบว่า ตัวแบบ Random Forests, XGBoost และ LightGBM มีผลลัพธ์การทำนายใกล้เคียงกันในแต่ละชุดตัวแปร และวิธีวิธีการปรับแต่งไฮเปอร์พารามิเตอร์ระหว่างการปรับให้เหมาะสมแบบเบย์ (Bayesian Search) และการค้นหาแบบสุ่ม (Random Search) ให้ผลลัพธ์ใกล้เคียงกันในแต่ละตัวแบบ …

A Query Engine For Self-Controlled Case Series, With An Application To Covid-19 Ehr Data, Xiaojin Li, Yan Huang, Licong Cui, Guo-Qiang Zhang

Faculty, Staff and Student Publications

Self-controlled case series (SCCS) is a statistical method in epidemiological study design that uses individuals as their own controls, with comparisons made within the same individuals at different time points of observation. SCCS has been applied in settings where it is difficult to identify comparison or control groups. To provide computational support for SCCS, we introduce a query engine called Self-Controlled Case Query (SCCQ) and use it to extract cohorts of self-controlled case series from a large-scale COVID-19 Electronic Health Records (EHR) dataset. Visual summary of the queried population through the R-Shiny visualization framework offers SCCQ's query result dashboard to …

Gene Expression In Mice With Endothelium-Specific Telomerase Knockout, Zhanguo Gao, Yongmei Yu, Yulin Dai, Zhongming Zhao, Kristin Eckel-Mahan, Mikhail G Kolonin

Faculty, Staff and Student Publications

No abstract provided.

Investigating Cellular Heterogeneity At The Single-Cell Level By The Flexible And Mobile Extrachromosomal Circular Dna, Jiajinlong Kang, Yulin Dai, Jinze Li, Huihui Fan, Zhongming Zhao

Faculty, Staff and Student Publications

Extrachromosomal circular DNA (eccDNA) is a special class of DNA derived from linear chromosomes. It coexists independently with linear chromosomes in the nucleus. eccDNA has been identified in multiple organisms, including Homo sapiens, and has been shown to play important roles relevant to tumor progression and drug resistance. To date, computational tools developed for eccDNA detection are only applicable to bulk tissue. Investigating eccDNA at the single-cell level using a computational approach will elucidate the heterogeneous and cell-type-specific landscape of eccDNA within cellular context. Here, we performed the first eccDNA analysis at the single-cell level using data generated by single-cell …

Contextual Variation Of Clinical Notes Induced By Ehr Migration, Kurt Miller, Sungrim Moon, Sunyang Fu, Hongfang Liu

Faculty, Staff and Student Publications

The structure and semantics of clinical notes vary considerably across different Electronic Health Record (EHR) systems, sites, and institutions. Such heterogeneity hampers the portability of natural language processing (NLP) models in extracting information from the text for clinical research or practice. In this study, we evaluate the contextual variation of clinical notes by measuring the semantic and syntactic similarity of the notes of two sets of physicians comprising four medical specialties across EHR migrations at two Mayo Clinic sites. We find significant semantic and syntactic variation imposed by the context of the EHR system and between medical specialties whereas only …

Digital Solutions Observed In Clinical Trials: A Formative Feasibility Scoping Review, Taylor M Harrison, Sungrim Moon, Liwei Wang, Sunyang Fu, Hongfang Liu

Faculty, Staff and Student Publications

Growing digital access accelerates digital transformation of clinical trials where digital solutions (DSs) are increasingly and widely leveraged for improving trial efficiency, effectiveness, and accessibility. Many factors impact DS success including technology barriers, privacy concerns, or user engagement activities. It is unclear how those factors are considered or reported in the literature. Here, we perform a formative feasibility scoping review to identify gaps impacting DS quality and reproducibility in trials. Articles containing digital terms published in English from 2009 to 2022 were collected (n=4,167). 130 articles published between 2016 and 2022 were randomly selected for full-text review. Eligible articles (n=100) …

Segmentation Of Acute Stroke Infarct Core Using Image-Level Labels On Ct-Angiography, Luca Giancardo, Arash Niktabe, Laura Ocasio, Rania Abdelkhaleq, Sergio Salazar-Marioni, Sunil A Sheth

Faculty, Staff and Student Publications

Acute ischemic stroke is a leading cause of death and disability in the world. Treatment decisions, especially around emergent revascularization procedures, rely heavily on size and location of the infarct core. Currently, accurate assessment of this measure is challenging. While MRI-DWI is considered the gold standard, its availability is limited for most patients suffering from stroke. Another well-studied imaging modality is CT-Perfusion (CTP) which is much more common than MRI-DWI in acute stroke care, but not as precise as MRI-DWI, and it is still unavailable in many stroke hospitals. A method to determine infarct core using CT-Angiography (CTA), a much …

Dental Claires: Contrastive Language Image Retrieval Search For Dental Research, Tanjida Kabir, Luyao Chen, Muhammad F Walji, Luca Giancardo, Xiaoqian Jiang, Shayan Shams

Faculty, Staff and Student Publications

Learning about diagnostic features and related clinical information from dental radiographs is important for dental research. However, the lack of expert-annotated data and convenient search tools poses challenges. Our primary objective is to design a search tool that uses a user's query for oral-related research. The proposed framework,

Keystroke-Dynamics For Parkinson's Disease Signs Detection In An At-Home Uncontrolled Population: A New Benchmark And Method, Shikha Tripathi, Teresa Arroyo-Gallego, Luca Giancardo

Faculty, Staff and Student Publications

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease disorder in the world. A prompt diagnosis would enable clinical trials for disease-modifying neuroprotective therapies. Recent research efforts have unveiled imaging and blood markers that have the potential to be used to identify PD patients promptly, however, the idiopathic nature of PD makes these tests very hard to scale to the general population. To this end, we need an easily deployable tool that would enable screening for PD signs in the general population. In this work, we propose a new set of features based on keystroke dynamics, i.e., the time …

The Health-Promoting Effects And The Mechanism Of Intermittent Fasting, Simin Liu, Min Zeng, Weixi Wan, Ming Huang, Xiang Li, Zixian Xie, Shang Wang, Yu Cai

Faculty, Staff and Student Publications

Intermittent fasting (IF) is an eating pattern in which individuals go extended periods with little or no energy intake after consuming regular food in intervening periods. IF has several health-promoting effects. It can effectively reduce weight, fasting insulin levels, and blood glucose levels. It can also increase the antitumor activity of medicines and cause improvement in the case of neurological diseases, such as memory deficit, to achieve enhanced metabolic function and prolonged longevity. Additionally, IF activates several biological pathways to induce autophagy, encourages cell renewal, prevents cancer cells from multiplying and spreading, and delays senescence. However, IF has specific adverse …