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NOx-responsive nitrogen-doped line defective graphene nanosensor
No full textRapid industrialization has led to environmental conditions that necessitate the design and development of advanced sensing devices capable of detecting gases at minute concentrations. In this paper, we present the design of a graphene-based device incorporating an extended 5-5-8 line defect along with nitrogen as a dopant in the lattice. Its structural, electronic, and transport properties of N-doped defective graphene and the adsorbed configuration with gas molecules, including CO, CO2, NO, NH3, and NO2 are investigated based on density functional theory. The results indicate that energetically stable N-doped defective graphene is semi-metallic and exhibits n-type doping characteristics. It interacts strongly with NO and NO2 compared to CO, CO2, and NH3 molecules. Electron transport calculations using the non-equilibrium Green\u27s Function method for N-doped system reveal the presence of an additional transmission channel at the Fermi level in comparison with a bare one, which significantly diminishes upon adsorption of NO/NO2 gases. Furthermore, NO and NO2 gases desorb more rapidly under UV radiation at room temperature. These results suggest that N-doped defective graphene can be a candidate nanomaterial for sensing NO and NO2 gas molecules
TRIBOELECTROSTATIC SEPARATION OF LUNAR REGOLITH
No full textLunar regolith as a source of raw materials for a long-term human presence on the moon would need to be separated into single mineral fractions. To do this, triboelectric properties can be utilized to separate minerals without needing to add a working fluid, such as air and water, or expensive, consumable chemicals. A lightweight machine can be created to do this, one that also requires minimal electricity. A series of three prototypes for this machine were created and tested to determine if this concept would work, and what properties the machine would need. A mixture of magnetite and silica were used in the testing since those can be separated easily with a magnetic separator to calculate the grade and recovery of the products created. It was determined that while the concept works, the prototype needs more refinement before testing with lunar regolith would be beneficial
MOLECULAR DYNAMICS MODELING OF HIGH-PERFORMANCE POLYMER MATRIX COMPOSITES
No full textPolymer matrix composites (PMCs) are widely used in the aerospace industries due to their outstanding mechanical and thermal properties, as well as their resistance to fatigue and corrosion, low dielectric constant, and low thermal expansion. During processing and manufacturing, these materials undergo multiple heating and cooling cycles, causing volumetric shrinkage in the polymer matrix, while the reinforcement remains unaffected. This shrinkage, resulting either from covalent bond formation during the curing of thermosets or from crystallization in semicrystalline polymers, can generate residual stresses, which negatively affect the final product\u27s performance. This study introduces a process modeling approach to minimize the formation induced residual stresses during manufacturing of composite materials for future Integrated Computational Materials Engineering (ICME) and Materials Genome Initiative (MGI) applications.
To address the induced residual stresses during the processing of composite materials, a comprehensive characterization of the resin is required. This process is both time-consuming and costly due to the complex nature of polymer resins. The evolution of thermo-mechanical properties must be studied as a function of processing parameters like temperature and processing time. In this research, a multiscale modeling approach is used to predict the evolution of thermo-mechanical properties of semi-crystalline PEEK as function of crystallinity content and processing time. Molecular dynamics (MD) and the Multiscale Generalized Method of Cells (MSGMC) have been employed to provide a comprehensive understanding of crystallization kinetics and evolution. All the predicted properties were compared to the experimental validation in the literature.
Additionally, this work examines the role of all-atom MD simulations in predicting the thermo-mechanical properties of polymer resins at the molecular level, particularly focusing on the system size\u27s effect on predictive precision and computational efficiency. A study on epoxy systems is conducted to determine the optimal system size, balancing accuracy and simulation cost.
Lastly, the research presents a process modeling framework for ArocyL10 which is a bisphenol E cyanate ester resins and highly valued in high-temperature applications due to their excellent thermal stability. To understand the effect of process parameter on the final properties of ArocyL10, MD simulations and cure kinetics modeling are utilized to predict the evolution of the volumetric shrinkage and thermo-mechanical properties of ArocyL10 as the curing progress at different curing cycles
DAM IT ALL: A MULTI-SCALAR INVESTIGATION INTO THE ECOLOGICAL ROLE AND FUNCTION OF BEAVER DAMS
No full textThe central theme of this dissertation is ecological scaling, which examines how small, localized features, such as beaver ponds, contribute to large-scale watershed processes and how different modeling approaches at various scales reveal distinct insights. Through a combination of probabilistic modeling and high-resolution empirical research, this work demonstrates that small ponded systems, particularly those created by beavers (Castor canadensis), serve as critical biogeochemical control points, whose contributions to sediment and nutrient dynamics have been historically underestimated.
In Chapter 1, I contextualize this research within the broader fields of freshwater ecology, watershed modeling, and ecological restoration. I introduce the theoretical basis for a dual-scale approach: one that recognizes the importance of fine-scale temporal variability in understanding nutrient cycling while also making the case for simplified, probabilistic models that enable large-scale ecological inference.
In Chapter 2, I present a Monte Carlo modeling framework used to estimate the historical density and ecological function of beaver dams across the contiguous United States. Results indicate that approximately 14.2 million beaver dams once retained 25.15 km³ of sediment and 1.08 million metric tons of phosphorus while supporting nearly 47,800 km² of wetland habitat. These findings affirm that beavers were once ecosystem architects at continental scales, capable of significantly shaping water quality and hydrology through their cumulative impacts.
In Chapter 3, I analyze high-frequency spatial and diel data collected from a single beaver pond to assess the dynamics of phosphorus cycling. The study reveals that soluble reactive phosphorus (SRP) concentrations vary by up to 20 µgP/L over 24-hour cycles and across pond zones. These fluctuations are likely driven by photosynthetic alkalinization, alkaline phosphatase activity, and acropetal nutrient transport, biologically mediated processes not commonly included in conventional models of internal loading. These results suggest that ponds are highly dynamic systems that do not conform neatly to lentic or lotic classifications.
In Chapter 4, I synthesize these findings and argue for a flexible, scale-explicit modeling framework in aquatic ecosystem research. Rather than viewing complex and simplified models as mutually exclusive, I propose that each scale of analysis contributes different but complementary insights. The large-scale modeling work reveals the historical ecological magnitude of beaver activity, while the small-scale observations show how local biological processes mediate nutrient cycling. I also emphasize the need for temporally resolved sampling in aquatic systems, as single-time-point sampling would have failed to detect the biogeochemical variability documented in this study. Collectively, this dissertation supports growing calls in freshwater science and restoration ecology to reintegrate beaver-mediated processes into watershed management, and it provides both empirical and theoretical contributions to the study of cross-scal
Origin of the World-Class Eagle, Eagle East, and Tamarack Ni-Cu-PGE Deposits
No full textThe 1.1 Ga Mesoproterozoic Midcontinent rift hosts the Eagle, Eagle East, and Tamarack Ni-Cu-PGE deposits and Embayment Prospect. These deposits are hosted by ultramafic igneous rocks and have some of the highest Ni-Cu grades on Earth. We use new bulk-rock data and published datasets (bulk-rock, mineral chemistry, and isotopic analyses) to examine major, minor, and trace element trends of both Midcontinent rift-related alkaline and tholeiitic intrusions. In addition, we compare the geochemical data to local kimberlite-hosted lower-crustal xenoliths and local igneous (Archean) and sedimentary (Paleoproterozoic) country rocks. We found the peridotite magma compositions dominantly consist of primitive mantle compositions with varying abundances of subduction-related components, alkaline-transitional melts, and local country rock contaminates (e.g., Baraga and Animikie Basin sediments). The subduction-related components are interpreted to be derived from previous Archean and Paleoproterozoic subduction events and likely hosted within the sub-continental lithospheric mantle. Importantly, these subduction-related components are also interpreted to have acted as oxidizing agents within the melt, stabilizing sulfate (+2 FMQ (fayalite–magnetite–quartz) to FMQ) while inhibiting sulfide crystallization as the magma ascended through ~50 km of the Superior craton. This study largely corroborates the previous findings with respect to the contribution of local country rock contamination to the Eagle–Tamarack peridotite host rocks, which is estimated to be minimal (\u3c 5%). However, the incorporation of \u3c 5% reductive pelitic siltstone contamination results in strong shifts in the oxygen fugacity of the peridotite melt, from +2 FMQ to slightly below FMQ, as determined from spinel Fe3+/∑Fe ratios. This shift in oxygen fugacity resulted in the transition from total sulfate (+2 FMQ) to sulfate + sulfide (\u3c +2 FMQ to FMQ) to total sulfide
The scintillator surface detector of the Pierre Auger observatory
No full textData collected so far by the Pierre Auger Observatory have enabled major advances in ultrahigh energy cosmic ray physics and demonstrated that improved determination of masses of primary cosmic-ray particles, preferably on an event-by-event basis, is necessary for understanding their origin and nature. Improvement in primary mass measurements was the main motivation for the upgrade of the Pierre Auger Observatory, called AugerPrime. As part of this upgrade, scintillator detectors are added to the existing water-Cherenkov surface detector stations. By making use of the differences in detector response to the electromagnetic particles and muons between scintillator and water-Cherenkov detectors, the electromagnetic and muonic components of cosmic-ray air showers can be disentangled. Since the muonic component is sensitive to the primary mass, such combination of detectors provides a powerful way to improve primary mass composition measurements over the original Auger surface detector design. In this paper, the so-called Scintillator Surface Detectors are discussed, including their design characteristics, production process, testing procedure and deployment in the field
Using Confidence Scores to Improve Eyes-free Detection of Speech Recognition Errors
No full textConversational systems rely heavily on speech recognition to interpret and respond to user commands and queries. Despite progress on speech recognition accuracy, errors may still sometimes occur and can significantly affect the end-user utility of such systems. While visual feedback can help detect errors, it may not always be practical, especially for people who are blind or low-vision. In this study, we investigate ways to improve error detection by manipulating the audio output of the transcribed text based on the recognizer\u27s confidence level in its result. Our findings show that selectively slowing down the audio when the recognizer exhibited uncertainty led to a 12% relative increase in participants\u27 ability to detect errors compared to uniformly slowing the audio. It also reduced the time it took participants to listen to the recognition result and decide if there was an error by 11%
Correlations between hemodynamics and radiomic features in thrombosed intracranial aneurysms
No full textPurpose: Evaluating intracranial aneurysm (IA) rupture risk is essential for guiding management. Although intrasaccular thrombosis (IST) is less common, it can contribute to aneurysm growth, mass effect, and rupture. Aneurysm wall enhancement (AWE) on high-resolution MRI (HR-MRI) offers valuable insight into IST and IA progression. Using radiomics, we extracted spatial information of the aneurysm wall to characterize AWE. This study aimed to explore correlations between radiomics-based AWE profiles and gross hemodynamic parameters, integrating imaging and flow dynamics to better understand IST. Methods: Radiomic analysis was conducted on a cohort of 3T HR-MRI scans from IA with IST. Three-dimensional vascular reconstructions and CFD simulations were conducted to quantify hemodynamic parameters. Spearman’s correlation was performed to correlate aneurysm morphology, AWE patterns, and aneurysmal hemodynamic characteristics. Results: A total of 37 thrombosed IAs were included in the analysis, comprising 22 fusiform (59.5%) and 15 saccular (40.5%) aneurysms. Six AWE RFs demonstrated strong correlations with aneurysm volume and surface area (ρ \u3e 0.7 for both). Ten AWE RFs were highly correlated with flow vortex parameters (ρ \u3e 0.7), and one showed a strong correlation with wall shear stress (WSS)-related metrics (ρ \u3e 0.7). In the subset of saccular IAs, 20 AWE RFs were strongly associated with WSS-related metrics. In contrast, fusiform IAs showed stronger correlations between AWE RFs and vortex core characteristics. These findings suggest that elevated AWE is closely associated with regions of high oscillatory shear index and unstable flow vortices, indicating a potential link between wall enhancement and disturbed intra-aneurysmal hemodynamics. Conclusions Stagnant flow may promote degenerative remodeling of the aneurysm wall and IST. A combined spatiotemporal analysis of hemodynamic parameters and AWE patterns provide information about underlying biological processes of IAs, including the development of IST
EXAMINING THE ROLE OF PLANT GENOME SIZE AND POLYPLOIDY IN SHAPING ARBUSCULAR MYCORRHIZAL FUNGI SYMBIOSES
No full textPolyploid and larger genome size plants have been shown to contain more cellular nitrogen and phosphorus than related diploid and smaller genome size plants, indicating they have greater nutrient requirements. Given that arbuscular mycorrhizal fungi (AMF) associations can enhance plant nutrient acquisition, polyploid and larger genome size plants may form more associations with AMF to meet their increased nutrient demands and gain greater benefits from these symbioses. However, because AMF associations become unnecessary when nutrient-rich soils meet plant needs independently, these interactions may be more likely to occur under nutrient-poor conditions. For this research, we conducted two experiments to examine how polyploidy, genome size, and nutrient enrichments influence plant responses to AMF and AMF root colonization patterns. In the first experiment, we grew diploid and polyploid Chamerion angustifolium under a full factorial combination of ambient or enriched nutrients and AMF presence or absence, and measured traits related to plant performance, resource-use, and AMF root colonization. We hypothesized that polyploids would exhibit greater AMF root colonization and gain more performance and resource-use benefits than diploids under ambient nutrients, but that differences in AMF root colonization and responses between diploids and polyploids would be reduced under enriched nutrients. Contrary to our predictions, we found that diploids exhibited greater performance and resource-use responses to AMF than polyploids under ambient nutrients, and that polyploids had higher AMF root colonization rates across both nutrient treatments. We found that neither cytotype benefitted significantly from AMF under high nutrients. In the second experiment, we sampled a grassland community with a range in genome sizes from both control and nutrient-enriched plots to test the hypothesis that AMF root colonization increases with genome size in ambient nutrient conditions and is less affected by genome size in nutrient-enriched conditions. We found that the influence of genome size was minimal, and that nutrient enrichment decreased AMF root colonization. Our findings highlight that genome size and polyploidy can have complex effects on plant-AMF interactions, and that these effects are further mediated by nutrient availability. This research provide greater insight into the role that polyploidy and genome size play in plant-AMF dynamics, an increasing crucial goal as shifts in nutrient availabilities worldwide are altering primary producer and multitrophic communities
WIP: Computation and Student Engagement in First-Year Engineering
No full textOur WIP describes an exploratory quasi-experimental study to determine if first-year engineering students\u27 academic motivation and engagement could be improved using WebTA. WebTA is a code critiquer to assist novice programmers in identifying issues in coding when first exposed to MATLAB. Utilizing Deci and Ryan’s Self Determination Theory, we hypothesized that WebTA would contribute to students’ needs for autonomy, relatedness, and competence, resulting in students who are more motivated and engaged, experience greater well-being and satisfaction, and develop stronger intrinsic motivation. Utilizing both the MUSIC Model of Motivation and Inventory, and a domain-specific motivation inventory, factor scores from both inventories were the dependent variables in a 2 X 2 design examining intervention (exposure to WebTA) and gender as independent variables. Significant interactions existed between intervention and gender on the MUSIC factor scores of empowerment, success, and caring. Women exposed to WebTA had significantly higher success, empowerment, and caring motivation than females in the control condition. In contrast, exposure to WebTA did not affect males’ perceptions of motivation. Additionally, there was no significant difference between male and female factor scores in the Web TA condition, whereas females in the control condition had significantly lower factor scores than men. These findings suggest that WebTA can be a powerful tool in improving women\u27s academic motivation and engagement, thus diminishing the gender gap in educational engagement