Scholarworks

A Photovoltaic Self-Powered Volatile Organic Compounds Sensor Based on Asymmetric Geometry 2D MoS2 Diodes

2025-02-05T19:17:33Z

dc.title: A Photovoltaic Self-Powered Volatile Organic Compounds Sensor Based on Asymmetric Geometry 2D MoS2 Diodes dc.contributor.author: Fawzy, Mirette; Reza Mohammadzadeh, Mohammad; Abnavi, Amin; De Silva, Thushani; Ahmadi, Ribwar; Ghanbari, Hamidreza; Kabir, Fahmid; Kavanagh, Karen L.; Hasani, Amirhossein; Adachi, Michael M. dc.description.abstract: Transition metal dichalcogenides have gained considerable interest for vapour sensing applications due to their large surface-to-volume ratio and high sensitivity. Herein, we demonstrate a new self-powered volatile organic compounds (VOC) sensor based on asymmetric geometry multi-layer molybdenum disulfide (MoS2) diode. The asymmetric contact geometry of the MoS2 diode induces an internal built-in electric field resulting in self-powering via a photovoltaic response. While illuminated by UV-light, the sensor exhibited a high responsivity of ∼60% with a relatively fast response time of ∼10 sec to 200 ppm of acetone, without an external bias voltage. The MoS2 VOC diode sensor is a promising candidate for self-powered, fast, portable, and highly sensitive VOC sensor applications.

2D MoSe2 Geometrically Asymmetric Schottky Photodiodes

2025-02-05T19:05:22Z

dc.title: 2D MoSe2 Geometrically Asymmetric Schottky Photodiodes dc.contributor.author: Ghanbari, Hamidreza; Abnavi, Amin; Ahmadi, Ribwar; Reza Mohammadzadeh, Mohammad; Fawzy, Mirette; Hasani, Amirhossein; Adachi, Michael M. dc.description.abstract: Optoelectronic devices based on geometrically asymmetric architecture have recently attracted attention due to their high performance as photodetectors and simple fabrication process. Herein, a p-type 2D MoSe2 photodetector based on geometrically asymmetric contacts is reported for the first time. The device exhibits a high current rectification ratio of ≈104 and a large self-powered photovoltage responsivity of ≈4.38 × 107 V W−1, as well as a maximum photocurrent responsivity of ≈430 mA W−1 along with a response time of ≈2.3 ms under 470 nm wavelength at 3 V bias voltage. The photocurrent responsivity is further enhanced to an ultrahigh responsivity of ≈1615 mA W−1 by applying a gate bias voltage due to the electrostatic modulation of carrier concentration in the MoSe2 channel. The simple fabrication process of the geometrically asymmetric MoSe2 diodes along with their high photodetection and diode rectifying performance make them excellent candidates for electronic and optoelectronic applications.

Elucidation of mechanisms of host plant resistance to wheat stem sawfly (Cephus cinctus Norton) in relation to antibiosis and the early stem solidness phenotype

2025-02-03T20:56:32Z

dc.title: Elucidation of mechanisms of host plant resistance to wheat stem sawfly (Cephus cinctus Norton) in relation to antibiosis and the early stem solidness phenotype dc.contributor.author: Hager, Megan Sunshine dc.description.abstract: In the North American Great Plains, wheat stem sawfly (WSS), Cephus cinctus Norton is a serious pest of cultivated cereals including common bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var durum). The solid stem phenotype is usually the basis of an effective management strategy in preventing infestation and yield loss in areas which experience pressure from large and damaging WSS populations. However solid stem expression can be negatively influenced by environmental effects and fully solid stems decrease the effectiveness of biological control of WSS by endemic parasitoids, highlighting a need for new sources of resistance outside of the solid stem phenotype. Here, we use 'omics technologies to comprehensively examine potential mechanisms of resistance including antibiotic resistance in oat, as well as small molecules, transcripts, photosynthetic parameters and volatile organic compounds in spring and durum wheat which help to explain decreased levels of infestation and lower incidence of stem cutting observed with the early solid stem phenotype. Genes and metabolites related to cellular organization, lignin composition and stem tissue structure appear to be involved in the resistance observed in oat and are also related to the early stem solidness phenotype in spring and durum wheat. Additionally, metabolic differences in abundance of lipids and carbohydrates were observed between oat and wheat as well as in spring and durum wheat near isogenic lines. Collectively, this research provides insight into the impacts that plant metabolites and gene expression may have on plant resistance to WSS.

Energy metabolism and mechanotransduction in osteoarthritic chondrocytes: targeted metabolic profiling and flux analysis

2025-02-03T20:56:32Z

dc.title: Energy metabolism and mechanotransduction in osteoarthritic chondrocytes: targeted metabolic profiling and flux analysis dc.contributor.author: Erdogan, Ayten Ebru dc.description.abstract: Osteoarthritis (OA) is a prevalent and debilitating disease that affects hundreds of millions people worldwide. One of OAs major consequences is the degradation of articular cartilage, leading to joint pain, stiffness, and loss of function. Currently, there is no treatment for OA. The existing interventions are mostly for suppressing the symptoms: physical therapy, anti-inflammatories, and pain management. The last resort is total joint replacement, which has long-term consequences especially for early-onset OA patients. Thus, researchers are focusing on understanding this complex disease and its molecular components to develop better treatments. Chondrocytes, the sole cell type in articular cartilage, play a crucial role in maintaining tissue homeostasis and responding to mechanical stimuli via synthesis of key structural components like collagen. However, the intracellular pathways underlying chondrocyte mechanotransduction are not fully understood, especially those related to central carbon metabolism. This thesis uses 13C isotopic labeling to trace carbon sources and downstream metabolites related to energy metabolism in vitro. Primary human articular chondrocytes from OA patients exposed to labeled glucose and glutamine, and their global and targeted metabolite profiles are assessed. The results show how both glucose and glutamine utilization as carbon sources flows through the TCA cycle. This work also develops a comprehensive model of mammalian carbon metabolism in OA primary human chondrocytes. The model integrates energy metabolism, amino acid synthesis, and transport reactions contributing to Collagen-II and Collagen-VI production. Using flux balance analysis (FBA), trade-offs between Collagen-II and Collagen-VI synthesis are evaluated based on ATP and carbon source requirements under different oxidative stress conditions. Then, these model predictions are presented with experimental data obtained from OA chondrocytes subjected to shear and compressive mechanical stimulation, which can be integrated in the model later on. These data shed new light on metabolism of primary OA chondrocytes and provides insight into potential therapeutic targets for OA intervention.

Interferometric methods for spatial-spectral holographic signal processing applications

2025-02-03T20:56:32Z

dc.title: Interferometric methods for spatial-spectral holographic signal processing applications dc.contributor.author: Wolfe, Owen Robert dc.description.abstract: Spatial spectral holographic (SSH) systems have applications in signal processing including spectrum analysis to optical correlation. Beam splitters and material interactions can affect the phase relationships between fields in separate spots in the material (or fields bypassing the material). Interferometric methods allow for these phase shifts to be exploited for two primary uses: the isolation of fields generated by the material and the amplification of signals and the amplification of signals in the chirped readout of programmed spectra. Stimulated photon echoes are used as the basis of SSH material-based optical systems and have been suggested as a protocol for optical quantum memory. These applications require the stimulated echo field to be isolated from a probe field. Current methods take an angular approach to isolating fields. An alternative approach uses interferometric methods to isolate fields in a way that can be implemented in a photonic integrated circuit. This dissertation will present a mathematical model for the isolation of stimulated photon echoes in both a 2-port Mach-Zehnder interferometer and a 4-port interferometer designed to emulate the isolation achieved via the angular "Box-Geometry" using interferometric methods. Experimental stimulated photon echo studies in a Mach-Zehnder interferometer built around a sample of 0.01% Tm 3+ : LiNbO 3 will demonstrate the principle of interferometric isolation of stimulated photon echoes. Maxwell-Bloch simulations will be used to demonstrate the principle of echo isolation in the 4-port interferometer. Use of the chirped interferometric readout of programmed spectra is demonstrated for SSH grating processing and spectrum analysis is shown in experiments in a sample of 0.01% Tm 3+ : LiNbO 3. Improvements to signal-to-noise ratio over traditional readout are seen by using a strong local oscillator in both applications. In spectrum analysis applications, the recovery of the proper spectral line shape is demonstrated, and SNR improvements are shown for a given read power. In the grating experiments, a non-linear noise floor was shown that created a constraint on the usable read power for these experiments. In this case, the interferometric readout was able to produce an improvement in the signal-to-noise ratio that could not be achieved using a stronger read power.

Development and optimization of open-source pumps and drop-based split-and-merge microfluidic devices

2025-02-03T20:56:31Z

dc.title: Development and optimization of open-source pumps and drop-based split-and-merge microfluidic devices dc.contributor.author: Sanchez, Humberto Scott dc.description.abstract: Drop-based microfluidics is used to encapsulate small volumes of chemical and biological agents into discrete drops. The contents of these pico-liter sized drops can then be used for biochemical assays. Microfluidic devices are used to manipulate these drops through the removal and addition of drop contents and pumps are used to control the fluid flow within the microfluidic devices. Often, the pumps used to drive fluid flow are prohibitively costly and the fluid dynamics of the devices used to control drop contents are not fully described. This research focuses on de-mystifying both the pump systems and microfluidic devices commonly used in drop-based microfluidics. We focused on developing an open-source pneumatic pressure pump to create microfluidic drops. Pneumatic pressure pumps have been found to be flexible and accurate systems to control fluid flow within microfluidic devices. Our pump system was found to be accurate and fast-responding as well as easy to assemble and control via open-source software. In addition, we developed a design process to develop drop-based split-and-merge (SAM) microfluidic devices. These devices have been commonly used to control drop volumes and add reagents for intra-drop assays. Our design and optimization methodology was then used to develop multiple SAM geometries with various splitting capabilities and the ability to create a broad range of drop volumes. The operating conditions for each SAM device was optimized for different input drop volumes. We also developed an empirical drop model to predict drop volume changes within a SAM device. Our open-source pneumatic pressure pump is a fast responding and accurate system that can be adapted for driving flow in any microfluidic device. Our drop-based SAM devices and the development and modelling process we developed serves as a blueprint for future SAM devices and similar drop manipulation microfluidic devices.

Facility-level quality of service analysis methodology for rural highways

2025-02-03T20:56:31Z

dc.title: Facility-level quality of service analysis methodology for rural highways dc.contributor.author: Raza, Sajid dc.description.abstract: Rural highways constitute a significant portion of the national highway system, serving vital mobility and freight movement functions while connecting towns and small cities separated by rural areas. As urban areas expand further from central cities, rural highways are experiencing increased traffic demand, posing challenges to maintaining an acceptable level of operational performance and quality of service. To evaluate the operational performance and quality of service of highways, the Highway Capacity Manual (HCM) offers a comprehensive set of tools and methodologies. It incorporates analytical methodologies to perform operational analyses for individual highway components (segments and intersections). It also offers facility-level analysis methodologies for freeways and urban streets only. In this context, a facility is defined as a stretch of highway consisting of multiple components. However, the current HCM lacks a facility-level analysis methodology for rural highways which is essential for evaluating extended lengths of rural highways. A rural highway facility consists of any combination of two-lane highway segments, multilane highway segments, and intersections (signal, stop control, or roundabout intersections). To address this limitation within the HCM framework, this research aims to develop a methodology for facility-level analysis of the quality of service for rural highways, thus adding to the existing tools and capabilities of the HCM. The proposed methodology, intended for inclusion in the next HCM edition, focuses on the interaction between contiguous segments and the operational impact of intersections on connected segments. In the course of developing the analysis methodology for rural highway facilities, this research needed to develop procedures for facility segmentation, which is a critical step in developing and applying the proposed methodology. To this end, the research used extensive vehicle trajectory data from multiple sites in estimating the upstream and downstream influence areas for three different types of intersections: signalized intersections, stop-controlled intersections, and roundabouts. Specifically, quantile regression models were developed to estimate the influence areas for the three different types of rural intersections. The proposed analysis methodology significantly enhances the ability of transportation analysts to assess operations along extended lengths of rural routes, allowing more effective planning and management of these important highway facilities.

From cross faults to lake deposits: geologic evidence of past and present hazards

2025-02-03T20:56:31Z

dc.title: From cross faults to lake deposits: geologic evidence of past and present hazards dc.contributor.author: Giri, Bibek dc.description.abstract: The Everest region in the eastern Nepal Himalaya is a natural laboratory for Earth sciences research as it consists of spectacular rock exposures, glaciers, lakes, rivers, and rockslide zones. While a plethora of research has been conducted in the region, a geomorphic and a tectonic feature remained unnoticed until recently. In 2017, a segment of a young (<12 Ma), NNE-striking cross fault, later named the Benkar Fault Zone (BFZ), was recognized and examined within the Everest region. Cross faults are faults that strike at a high angle to the trend of the orogen. The BFZ remained unexplored towards the south. Secondly, there are a number of layered, sandy deposits, around the Namche-Phortse areas, perched high on hillsides with no obvious connection to a modern depositional basin. The goals of my dissertation are to explore these unanswered questions in order to: 1) understand the southern continuity and genesis of the BFZ; and 2) constrain depositional ages for those sandy deposits and understand their depositional settings. To achieve my first goal, I mapped the BFZ towards the south from the Everest region and augmented the mapping results with kinematic and petrographic analysis. I find that the BFZ is a ~100 km long, segmented cross fault zone that possibly cuts across the entire width of the eastern Nepal Himalaya. The BFZ is a composite of a series of deformational events and might continue further towards the south into the foreland basin. This fault, like other Himalayan cross faults, likely contributes to seismic and landslide hazards. Through an extensive literature review, I have synthesized the occurrences and drivers of cross faults and lateral heterogeneity in several mountain belts around the world. For my second goal, I constrained the depositional ages of six sedimentary deposits by utilizing infrared stimulated luminescence analysis and integrated the ages (~13-42 ka) with their geomorphic setting. I interpret that some of them were likely deposited in localized, landslide- and/or moraine-related, ephemeral lakes/ponds. Such deposits provide invaluable agricultural land in these extreme topographies.

Childhood trauma and health: an investigation of physiological, behavioral, cognitive, and emotional pathways.

2025-02-03T20:56:30Z

dc.title: Childhood trauma and health: an investigation of physiological, behavioral, cognitive, and emotional pathways. dc.contributor.author: Counts, Cory Joe dc.description.abstract: Childhood trauma poses serious risk for overall health. Prior research has identified major pathways connecting childhood trauma to increased risk for poor health across many domains of health. The current project builds on this literature. Some prior research suggests that physiological stress responses in adulthood are blunted for individuals who experience childhood trauma compared to those who have not. Theory suggests that different patterns of physiological stress reactivity may be linked to different perceptions of environmental demands and resources to cope. The project aimed to investigate childhood trauma and blunted physiological reactivity to stress mediated by dissociative responses. Dissociation is a psychological and physiological mechanism thought to protect an individual from stressors that are inescapable or outweigh an individual's abilities to overcome stress. Separately, the perception of childhood trauma burden later in life may predict the degree to which childhood trauma affect health-relevant outcomes in adulthood. Previous research has shown that individuals who perceived their childhood trauma as more burdensome may be at higher risk for poor mental health. In separate research, emotion regulation strategy usage is related to mental health. The possibility exists that differences in childhood trauma burden and emotion regulation strategies used to cope with emotions may interact to inform differences in mental health. The current project addresses the following. Study 1 tested whether childhood trauma is linked to blunted physiological responses to a social-evaluative in-lab stressor, and proposed to test whether this relationship is in part mediated by increased dissociative responses to the stressor. Study 2 tested whether childhood trauma was linked to more dissociative responses to daily stressors, and whether childhood trauma and dissociative responses to daily stressors interacted to predict objective markers of sleep quality in a 6-day data collection period. Study 3 explored the relationship between perceived childhood trauma burden, emotion regulations strategies, and mental health in a sample of American Indian adults nationwide. The findings from Study 1+2 did not confirm hypotheses. The implications of the results are discussed. Study 3 was exploratory and the observed results are discussed. The implications, limitations, and future directions for the 3-part study results are discussed.

An expanded lava creek tuff eruption: re-mapping the Sour Creek Dome, Yellowstone National Park

2025-02-03T20:56:30Z

dc.title: An expanded lava creek tuff eruption: re-mapping the Sour Creek Dome, Yellowstone National Park dc.contributor.author: Salazar, Raymond Dale dc.description.abstract: The ~1000 km 3, ~630 ka Lava Creek Tuff is the product of the younger major caldera- forming eruption of the Yellowstone Volcanic Field. It is currently mapped as two ignimbrite units, hot dense flows of ash, gas, and molten material, termed members A and B, with accompanying widespread ashfalls over the western U.S. This view of the Lava Creek Tuff, and its eruption, was complicated when two, visually distinct, ignimbrites were recognized on the Sour Creek dome in Yellowstone National park (Wilson et al., 2018). These visually distinct ignimbrites on the Sour Creek dome were initially mapped as the older (2.08 Ma) Huckleberry Ridge Tuff, however, when dated by U - Pb on zircon and 40Ar/39Ar on sanidine the ignimbrites returned ages analytically indistinguishable from the Lava Creek Tuff (0.631 Ma). In the newly dated ignimbrites, one unit is found as clasts of dense welded tuff withing a lag deposit which is conformably overlain by a second, cliff-forming, densely welded ignimbrite that contains scoria. This study further complicate matters due to the discovery of two additional, previously unrecognized, ignimbrites while mapping on the Sour Creek dome, bringing the total to four ignimbrites. Physical and chemical evidence suggests there were multiple magma bodies tapped during the eruptions. This project broadens our understanding of the four ignimbrites documenting their spatial distribution and source area(s) and determine how they relate geochemically to the established members A and B. This was done through field mapping, thin section examination, and whole-rock and single crystal geochemistry. This resulted in a revised understanding of the Lava Creek Tuff stratigraphy and holds implications for reevaluating the eastern boundary of the Yellowstone Caldera.