Digital Commons Network^™

The Fate Of Organic Nitrogen In Agroecosystems: Drivers And Outcomes, Lauren C. Breza

Doctoral Dissertations

Enhancing soil nitrogen (N) stocks is critical for managing soil health in agroecosystems. Growers apply external N as synthetic fertilizer to increase the amount of available N to crops. However, it is well known that synthetic fertilizer usage in agroecosystems leads to widespread pollution and contributes significantly to climate change. Nevertheless, growers and researchers recognize this N problem as a global problem and are developing solutions via alternative farming methods. Some of these alternative strategies include cover cropping, diversifying crop rotations, organic farming (i.e., no inputs), or combining these methods. Understanding how the different facets of agricultural management influence the …

Substorm Onset Related Ultra Low Frequency Waves, Michelle Salzano

Doctoral Dissertations

Ultra Low Frequency (ULF) waves are geomagnetic perturbations in the mHz to Hz range that contribute both directly and indirectly to particle losses in the radiation belts. Pi1B waves are ULF broadband bursts in the Pi1 range that are well correlated with substorm onset. Intervals of Pulsations of Diminishing Periods (IPDPs) are a sub-type of ULF Electromagnetic Ion Cyclotron (EMIC) waves that are characterized by an increase in frequency over time. IPDPs are thought to be generated by particles injected at substorm onset. One of the main instruments used to identify ULF waves is the searchcoil magnetometer. In this dissertation, …

First-Year Students And Writing Support: Learning From Student Choices, Alicia Clark-Barnes

Doctoral Dissertations

In 2022, COVID-19 has disrupted the academic experience of students, including students access to writing support. The importance of the support universities offer and that students are able to access has greatly increased as offerings and circumstances shift and change. Students seeking support may turn to university-sponsored services but if those do not fit student needs, students may rely on informal supports, including friends and family. While investigating the gaps in university-sponsored writing support first-year students experience, I explore how first-year students understand what writing support is, how available/accessible it is to them, and why students return to a form …

Answering Topical Information Needs Using Neural Entity-Oriented Information Retrieval And Extraction, Shubham Chatterjee

Doctoral Dissertations

In the modern world, search engines are an integral part of human lives. The field of Information Retrieval (IR) is concerned with finding material (usually documents) of an unstructured nature (usually text) that satisfies an information need (query) from within large collections (usually stored on computers). The search engine then displays a ranked list of results relevant to our query. Traditional document retrieval algorithms match a query to a document using the overlap of words in both. However, the last decade has seen the focus shifting to leveraging the rich semantic information available in the form of entities. Entities are …

Neighborhood Disorder And Adolescent Psychological Distress: Effects Of Gender, Race/Ethnicity, Social Support, And Self Concept, Jean Bessette

Doctoral Dissertations

Sociological research on mental health is often guided by the stress process framework. A key tenet of this paradigm is the proposition that both exposure and vulnerability to social stressors arise from one’s placement in the social structure; those with lower social status face greater exposure and/or greater vulnerability to stressors that detrimentally impact their psychological wellbeing. A consequential social stressor is the neighborhood context in which one resides. Past research has suggested a disadvantageous effect of greater neighborhood physical and social disorder on youth mental health. This research employs the stress process framework to examine how the effects of …

Environmental Implications Of Ubiquitous Dicarboxylic Acid Aerosol And Biomass Burning Generated Reactive Nitrogen, Jackson Hart Kaspari

Doctoral Dissertations

Aerosols impact our lives in many different ways, including the health of our species,visibility and the global climate. In terms of climate effects, large uncertainty still exists surrounding the combined influence of aerosols on the Earth’s radiative budget. This highlights the importance of research that seeks to better understand atmospheric aerosols and associated gas phase compounds, as advances in the field will allow for the production of more accurate climate models. In laboratory studies, great variability in reported deliquescence relative humidity (DRH) warrants the need for new methods of analysis. A custom built electrobalance with variable active particle humidity control …

Self-Validated Ensemble Modelling, Trent Lemkus

Doctoral Dissertations

An important objective when performing designed experiments is to build models that predict future performance of a system in study; e.g. predict future yields of a bio-process used to manufacture therapeutic proteins. Because experimentation is costly experimental designs are structured to be efficient in terms of the number of trials while providing substantial information about the behavior of the physical system. The strategy to build accurate predictive models in larger data sets is to partition the data into a training set, used to fit the model, and a validation set to access prediction performance. Models are selected that have the …

Narratives Of Becoming: Conceptualization Of Teacher Identity Through The Experiences Of Educators From Racially, Linguistically, And Culturally Minoritized Backgrounds, Sumeyra Gok Gulmezoglu

Doctoral Dissertations

Teacher education programs are predominantly White spaces with their faculty, teacher candidates, curriculum, and practices. In these spaces, the experiences of teacher candidates from minoritized backgrounds can be alienating and their voices can be overlooked or silenced. In three interrelated but distinct studies, this research aims to highlight the experiences and perspectives of educators from minoritized racial, ethnic, and linguistic backgrounds as they are conceptualizing their professional identities as educators. These three studies are narratives of becoming as they explore conceptualization of teacher identity through three different narrative methods namely autoethnography, counterstories, and narrative inquiry. Although each study has its …

Estimation And Consequences Of Asymmetric Dispersal On The Genetics Of Coastal Marine Organisms In 1-D Habitats, Kyle Teller

Doctoral Dissertations

Estimation and Consequences of Asymmetric Dispersal on the Genetics of Coastal Marine Organisms in 1-D Habitats

Many natural populations have a dispersal that is biased in one direction (asymmetric dispersal), due to physical factors in the environment such as currents in the ocean that transport larvae or winds that carry seeds. These physical factors create a preferred direction for offspring to be carried (the “downstream” direction). When there is asymmetric dispersal there are two parameters that define the dispersal distance, the mean downstream distance, and the standard deviation of dispersal distances. This present research analyzes the effects of the mean …

Scale Formation, Properties And De-Scaling In Steelmaking, Richard Osei

Doctoral Dissertations

During continuous castings, reheating, and hot rolling, slab surfaces are exposed to atmospheres containing oxidizing gases which results in scale formation. Inefficient removal of the formed scale during reheating affects product surface quality. The effect of steel composition and operating parameters on scale formation and scale removal efficiencies were investigated. Experimental investigations were carried out using a thermogravimetric (TGA) apparatus designed to replicate the combustion gas atmosphere and temperature in actual industrial slab reheat furnaces. Report on oxidation kinetics, scale structure and properties, and descaling were conducted on laboratory cast and industrial samples. Different characterization techniques were used to analyze …

Multifunctional Behaviors Of Two-Dimensional Materials And Their Composites, Yanxiao Li

Doctoral Dissertations

"Two-dimensional (2D) materials, including graphene, transition metal carbides or nitrides (TMC/Ns), have rich surface chemistry, superb electrical and mechanical properties. These unique properties make them ideal for multifunctional devices. Among them, we focused on graphene and TMC/Ns (i.e., MXenes), as well as their composites. Unlike the well-known graphene, MXenes, are relatively new and typically synthesized by the selective etching of the “A” layers from the layered carbides and /or nitrides known as MAX phases, which introduce MXenes with rich terminal groups (e.g. -O-, -OH, -F).

During my Ph.D. study, firstly, the adhesive and frictional behaviors, which are related to successful …

Effects Of Teaching Argument To First-Year Community-College Students Using A Structural And Dialectical Approach, Sharon Radcliff

Doctoral Dissertations

The purpose of this study was to measure to what extent an experimental method of teaching argument incorporating elements from both Toulmin’s (2004) structural approach and Walton’s (2013) dialectical approach effects first-year college students’ ability to write strong arguments. This experimental instruction used critical questioning as a strategy in building a strong argument, incorporating alternative viewpoints, and creating a dialogue between claims and counterclaims, backed logically by verifiable evidence from reliable sources.

Using the Analytic Scoring Rubric of Argumentative Writing (ASRAW; Stapleton & Wu, 2015) that includes the argument elements of claims, data, counterclaim, counterclaim data, rebuttal claim, and rebuttal …

Impact Of Covid-19 On New Teacher Retention And Perceived Supports In A Northern California Public School District, Rebecka Maxkenzie

Doctoral Dissertations

This qualitative study examined teachers, schools, and district approaches to new teacher retention with a COVID-19 spin. In the changing world of a global pandemic and shifting teaching modalities, including distance or hybrid learning environments, teachers reflected on their experiences of adaptation. Interviews with teachers in their first three years in the profession were conducted to share the stories of new teachers amid COVID-19. New teachers were recruited through a snowball sampling technique from a large school district in the San Francisco Bay Area in Northern California. To answer the research questions, participants were interviewed about the presence or absence …

Voces Of Little Michoacan: A Collective Narrative Of Resistance And Preservation Of Home, Ana Angel Avendaño

Doctoral Dissertations

This empirical study captured the ongoing community organizing, led primarily by Chicanas and young people in a Latinx community in the San Francisco Bay Area. This community has experienced historic neglect, inequities, gentrification, and economic displacement. Through muxersita portraiture, a critical qualitative methodology, with young people as co-researchers, this study captures the collective narrative of the community of North Fair Oaks through platicas, encuentros y acción. In the process, this collective narrative disrupts the negative impact of gentrification by providing a historical context of the contributions of Latinx in North Fair Oaks. This study uses a critical coraje framework; a …

¿Tú Qué Sabes?: Latina Doctoral Women Disrupting And Resisting Dominant Knowledge, Sendy Ramos Madsen

Doctoral Dissertations

Education environments have systematically excluded, silenced, and erroneously spoken on behalf of Women of Color. Linear forms of scholarship and research practices propagate the dominant perspective and fail to address systems of oppression that result in epistemic suppression and academic hostility towards brown minds. Historically, Latina women have not been seen as creators of knowledge, and their access to educational spaces has been restricted. According to census projections, in 2036, Latinas/os will account for the largest minority group in the United States and one-third of the American educational system. Therefore, academic spaces must establish practices to include Latina women as …

Design Methods For Pressure Relief Well Systems At Dams And Levees, Andrew Keffer

Doctoral Dissertations

"Flood risk reduction structures such as dams and levees are important systems that provide significant benefits to the nation. Relief wells reduce the substratum water pressures that can compromise them via internal erosion. The U.S. Army Corps of Engineers (USACE) analytical method to design relief well systems by calculating discharge and excess head along an infinite line of wells was developed from the 1930s – 1950s. The research presented here increases our understanding of the method’s history and uses analytical and numerical models to improve current infinite and finite well system design practices. The historical development of this method was …

Strategies To Improve Shrinkage Resistance Of Cement-Based Materials For Extrusion-Based 3d Printing, Kavya Vallurupalli

Doctoral Dissertations

"The main objective of this study is to develop new generation of shrinkage-resistant 3D printable mortar mixtures. To this end, the research work was carried out to: i) identify key material and processing parameters that affect printability; ii) investigate the influence of water-to-cement ratio, superplasticizer dosage, and welan gum content on mortar printability; iii) propose a “printability window” where rheological properties and desorptivity can secure successful printing; iv) investigate effect of shrinkage mitigation materials (expansive agent (EA), pre-saturated lightweight sand (LWS), superabsorbent polymers (SAP), and shrinkage reducing admixture) on printability and shrinkage performance of mortar; and v) evaluate the effect …

Synergistic Effect Of Shrinkage Mitigating Strategies On Performance Of Fiber-Reinforced Cementitious Composites, Kamran Aghaee

Doctoral Dissertations

"The advantages of using shrinkage mitigating strategies to reduce shrinkage and mitigate cracking of concrete is well documented. However, the benefits and drawbacks of employing multiple strategies have not been explored. The main objective of this study is to provide insights into the mechanisms of using multiple strategies to enhance shrinkage and cracking resistance to promote the properties of high-performance cementitious composites (HPC) designated for infrastructural construction, repair, and 3D printing applications. HPC mixtures were prepared with steel and synthetic macro and microfibers, expansive agent (EA), and shrinkage reducing admixture (SRA) coupled with various curing methods e.g., internal curing using …

Advanced Materials And Processes For Gas Separation And Storage Applications, Qasim Mohammed Al-Naddaf

Doctoral Dissertations

"Transition to a clean, renewable energy future requires departure from thermally driven separation processes. In that regard, development of new materials that exhibit high adsorption capacity and selectivity, fast kinetics, and long-term durability under multicomponent conditions is becoming attractive for the applications in clean energy. Moreover, novel sorbents and separation systems that can store gases at normal conditions offer a promising approach for stationary or onboard gas storage. Due to the limitations on the surface area and biding energy restrict commercial materials effectiveness as a potential adsorption and storage material. There is significant interest in the properties of hybrid materials …

Depression Of Pyrite In Polymetallic Sulfide Flotation Using Chitosan-Grafted-Polyacrylamide Polymers, Keitumetse Cathrine Monyake

Doctoral Dissertations

“In this work, Chitosan-grafted-Polyacrylamides (Chi-g-PAMs) were studied, for the first time, as selective depressants of pyrite in the flotation of base metal sulfides. Fundamental studies of the adsorption behavior of Chi-g-PAM on model sulfide minerals indicated that Chi-g-PAM was more selective to pyrite’s surfaces as compared to base metal sulfides. Results suggested that the adsorption of Chi-g-PAM at pyrite-water interface was a chemisorption in nature which involved the amine, amide, and hydroxyl groups of Chi-g-PAM. Batch flotation studies of complex sulfide ore of Mississippi Valley Type (MVT) showed that Chi-g-PAM outperformed other pyrite’s depressants at producing less pyrite-diluted concentrates. Statistical …

Groundwater Withdrawal Estimation Using Integrated Remote Sensing Products And Machine Learning, Sayantan Majumdar

Doctoral Dissertations

"The rising demands for water, food, and energy primarily driven by the increasing global population constitute a pressing issue worldwide. Therefore, the water-food-energy nexus plays a substantial role in developing globally applicable sustainable solutions. Recent technological advancements, including the earth observation programs using spaceborne remote sensing platforms, have enabled us to monitor various critical components affecting the globe. Groundwater, which comprises the world's 30% freshwater, is one such key component of the global water resources and supplies nearly half of the global drinking water.

Despite groundwater overdraft in many parts of the world, including the United States (US), there are …

Synthesis And Process Optimization Of Colloidal Unimolecular Polymer, Cup, Particle Formation, And Its Interfacial Surface Tension Behavior, Ashish Zore

Doctoral Dissertations

"Colloidal Unimolecular Polymer (CUP) particles are 3-9 nm size single-chain polymer nanoparticles that are made from amphiphilic acrylic co-polymers using the process of water reduction. The formation of CUP particles was driven by the polymer-polymer interactions being greater than polymer-solvent interactions as well as the charge-charge repulsion due to the increasing dielectric of the medium. CUPs provide a surfactant or additive-free nanoparticle system that was useful for studying the interfacial behavior of pure aqueous nanoparticles using a maximum bubble pressure tensiometer. The equilibrium surface tension shows a dependence on concentration and the charge density of the CUP particle. The equilibrium …

Development Of An Interactive Robot For Overground Physical Human-Robot Interaction, Sambad Regmi

Doctoral Dissertations

"The overground interactive robots are potentially beneficial for humans in various areas, such as overground rehabilitation therapies and robotic interactive assistance. However, it is unclear what the expectations and challenges are for a robot to be physically interactive with a human during overground tasks, such as a robot helping an older adult walk. To develop such a robot, one must first build a clear understanding of how the human motor intent is communicated when interacting with another agent. Specifically, how do humans understand the leader’s intention when being led?

Based on previous works, we hypothesized that humans modulate their arm …

Sustainable Face Milling Of Inconel 718 Using Mql And Nanofluids Mql With Vegetable Oil As Base Fluid, Theodore Obumselu Nwoguh

Doctoral Dissertations

"Extreme heat and friction are generated in machining difficult-to-cut metals used in aerospace and nuclear industries leading to poor machinability (high cutting forces, rapid tool wear, shorter tool life, and poor surface integrity). Conventional flood coolant (CEC) used in industry is environmentally unfriendly, hazardous to operators, and unsustainable. These problems motivated this research, which can be mitigated with the use of effective biodegradable cutting fluids, appropriate cutting conditions, and lubrication/cooling strategies. This research provides a sustainable and environmentally friendly replacement to CEC. Firstly, the research characterized three vegetable oils (High Oleic Soybean Oil (HOSO), Low Oleic Soybean Oil (LOSO), and …

Design And Performance Of Self-Consolidating And Thixotropic Ultra-High-Performance Concrete For Infrastructure Construction And Rehabilitation, Le Teng

Doctoral Dissertations

"The objective of this research is to develop two classes of ultra-high-performance concrete (UHPC), one with self-consolidating consistency and the other with improved thixotropy. Tailoring the rheological properties of low yield stress UHPC can improve dispersion and orientation of steel fibers used in the design of UHPC, hence enhancing the tensile and flexural properties. Similarly, improving the thixotropy of UHPC can enable unique performance for the design of thin bonded bridge deck overlay. The research investigated various thixotropy enhancing admixtures to enhance the structural build-up at rest of UHPC. A total of 16 bonded overlay slab specimens were used to …

Establishing Pteridine Metabolism In A Breast Cancer Cell Model And Quantification Of Silver Nanoparticle Interactions With Yeast Cells Using Mass Spectrometry, Lindsey Katherine Rasmussen

Doctoral Dissertations

"Recent advances in analytical methods have furthered the quantitative insights that can be gleaned from cellular analyses, with applications in cancer and nanoparticle research. In the first part of the research presented, a recently developed HPLC-MS/MS method was advanced to elucidate pteridine metabolism in an isogenic progressive MCF10A breast cancer cell model. The folate-derived pteridine pathway in breast cells was established by individually dosing cell cultures with folic acid and 15 pteridines. Eight potential pteridine biomarkers in breast cancer cells were identified including pterin and isoxanthopterin, which yielded the first in vitro evidence for the cellular metabolisms behind previously reported …

Use Of Cellular Concrete For Air Convection Embankment To Protect Permafrost Foundation In Cold Regions, Hanli Wu

Doctoral Dissertations

"Crushed-rock air convection embankment (ACE) has been used to mitigate thaw settlement, and pavement distresses caused by climatic extremes in permafrost regions for over three decades. However, the desired crushed rocks needed for ACE are not readily available in many areas of interior Alaska. Burdened by the need to ship suitable rocks to remote locations, the cost of constructing an ACE is often prohibitively high, which prevents its wide use in Alaska. An existing cementitious material, cellular concrete, may provide the solution.

This study intends to systematically characterize the heat transfer patterns of ACE and identify the performance benefits of …

Design And Synthesis Of Purine Based Neuroprotectors And Novel Synthetic Methods For The Trifluoromethylation Of Aldehyde Hydrazones, Puspa Aryal

Doctoral Dissertations

"Purine-derived compounds are widely investigated as cyclin-dependent kinase inhibitors that have broad applications in the design of pharmaceuticals for treating diseases, such as diabetes, atherosclerosis, and cancers. Towards the goal of effective AGE-inhibitors, and neuroprotector compounds we have synthesized a series of novel purine-based triazoles and investigated their neuroprotective effects, using SHSY-3Y human neuroblastoma cell line. Through these studies, we have identified purine-based neuroprotector compounds that favorably modulate oxidative stress induced by the Fenton reaction-generated reactive oxygen species (ROS).

The C(sp²−H)-trifluoromethylation of hydrazones would give access to the αtrifluoromethylated hydrazones that can serve as intermediates in the synthesis …

Pi And Emi Analysis Of 3d Ic System With Tsvs And Co-Packaged Optics, Wei Zhang

Doctoral Dissertations

"With the demand for developing high-capacity, high-density, high-power optical links for data center communications, co-packaged optics is a promising solution. When the three-dimensional (3D) IC and optic engines are integrated into the same package, the design of such systems in terms of signal integrity, power integrity, and electromagnetic interference will be more challenging.

This first paper mainly focuses on modeling the bias-voltage-dependent, temperature-dependent, and light-intensity-dependent hysteresis behavior of a through-silicon-vias (TSV) structure in 3D IC and analyzing its effect on the power integrity of a system with 3D IC.

This second paper investigates the scaled tendency of the emissions in …

Evaluation Of Novel Preformed Particle Gels For Conformance Control And Acid Stimulation Through Core Flooding Tests, Shuda Zhao

Doctoral Dissertations

"Acid stimulation and conformance control are two major methods to improve oil production. This study systematically evaluates two newly developed gels: Degradable Preformed Particle Gel (DPPG) and Re-crosslinkable Preformed Polymer Gel (RPPG). DPPG is designed to be a temporary plugging agent for acid stimulation and can self-degrade into a water-like fluid. RPPG is designed for reservoir sweep efficiency improvement and can re-crosslink to each other and form an immobile bulk gel after being placed in fractures or fracture-like conduits.

For DPPG, this study evaluates the effect of monomer, crosslinker, and initiator concentration on the swelling and degradation performance. Results show …