79717 research outputs found
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Managing soil acidity for no-till wheat production and establishing lime recommendations for pH targets above 6.4 for Oregon soils
No full textSoil acidity is an emerging constraint to wheat production in the inland Pacific Northwest (iPNW), driven by long-term ammonium N fertilizer use. This thesis evaluated the effectiveness of calcium (Ca) amendment strategies—including lime and gypsum sources with different placements—on ameliorating soil acidity, reducing aluminum (Al) toxicity, and improving winter wheat (Triticum aestivum) performance in extremely acidic 0-7.5 cm A horizon Walla Walla silt loam (pH 3.8, 189 mg Al kg-1). Eight treatments (no lime control, incorporated ag lime, surface-applied ag and prilled lime, banded prilled and fluid lime, and incorporated and surface-applied gypsum) were tested in a greenhouse trial for effects on soil chemistry and plant growth.
Incorporated lime significantly improved soil pH to 5.3, reduced Al saturation to 4%, and produced the highest root biomass (2.73 g pot⁻¹), shoot biomass (24.3 g pot⁻¹), and grain yield (21.4 g pot⁻¹). Surface lime rose to pH 5.8 and 6.0 at the 0-5 cm depth, and moderately improved wheat shoot and grain biomass. Banded lime and gypsum did not significantly affect soil pH or wheat performance, likely due to low application rates or lack of pH reactivity. Results indicate lime incorporation is the most effective strategy for mitigating acidity and Al toxicity, especially in no-till systems which may have very acidic pH stratified layers in the upper 20 cm depth.
To complement the greenhouse study, a laboratory incubation study assessed lime requirements for seven Oregon soils—six of which are highly buffered—using CaCO₃ rates up to 81.1 Mg ha⁻¹. All soils reached pH ≥6.4 with lime rates >40.1 Mg ha⁻¹ lime, though pH gains plateaued between 7.2 and 7.6 depending on soil type. New linear regression models were developed for pH targets from 6.4 to 7.2 using Sikora and SMP buffer methods, improving predictive accuracy (R² = 0.91–0.93). These models provide fine-scale lime rate recommendations at 0.1-unit intervals.
Together, these studies address critical gaps in soil acidity management in Oregon. They offer practical guidance on lime placement, source, and rate for improved wheat performance, while extending lime requirement models to meet evolving grower needs, especially for clubroot disease suppression and high-value crop systems where higher soil pH is desirable.KEYWORDS: soil acidity, no-till, gypsum, limin
Towards Developing Pedestrian Safety, Efficiency, and Intuition at Signalized Intersections
No full textPedestrian behavior, including crossing decisions and pushbutton use, can have important implications on the safety and efficiency of signalized intersections. Pedestrians who cross against the pedestrian signal put themselves at greater risk of being involved in a crash, while pushbutton misuse can incur substantial delay for all intersection users. Prior literature has found that a wide variety of factors, including individual characteristics, social context, environmental factors, and infrastructure design can influence pedestrian decision-making. However, many of these studies do not investigate pedestrian pushbutton use or infrastructure, nor delve beyond the observational study to explore pedestrians’ mental models when approaching a signalized intersection. This dissertation presents a sequence of research exploring pedestrian decision-making at signalized intersections, beginning with a small-scale recruited participant study of pedestrian behavior and visual attention at one intersection, followed by larger-scale observational and recruited pedestrian studies at multiple intersections on or near the Oregon State University Corvallis campus. In these studies, most pedestrians crossed according to the pedestrian signal, visually attended to traffic signals and signage to support their decision-making, and used pushbuttons as intended—particularly at locations where pushbuttons were separated on different poles. However, pedestrians also reported that they could benefit from infrastructure modifications to support their decision-making. Therefore, four novel infrastructure concepts were developed and assessed
I'm a Jurassic Girl in an Anthropocene World: Movements of Adult White Sturgeon in the John Day Reservoir, Columbia River
No full textWhite sturgeon (Acipenser transmontanus) are indigenous to major river systems in the Western U.S. and Canada. Since the construction of the Federal Columbia River Power Systems, white sturgeon populations are reproductively isolated, impacting recruitment to the point of failure in some impoundments. To address population concerns in the John Day Reservoir, detection data from 58 adult white sturgeon tagged with 69kHz Innovasea/Vemco acoustic transmitters were used to quantify range and spawning movements. I quantified daily movement values associated with individuals across six years with eleven VR2W receivers. These values were used to classify six behavioral states with a randomForest model and calculate occupation time in each. The results showed that individual variation in occupation time of each behavioral state differed each year between sex and size. General trends demonstrated that white sturgeon hold in the McNary tailrace for the majority of the year with a greater occupation of other behaviors during warmer months. The results revealed occupation of the holding behavior in the lower third of the reservoir each year, as well as a substantial degree of the exploratory behavior observed in the mid-reservoir habitat. A General Linear Mixed Model (GLMM) tested the influential relationships of sex, size, and year on the occupation time in each behavioral state. These results indicated that sex and size influenced behavior in all of the years and that variation between years was significant for all behavior states. Detection data from a dense array of sixteen VR2AR receivers in the McNary tailrace, was used to generate location estimates based on correlated random walk (CRW) in a state space model. Movements were extrapolated with a joint movement persistence model and paired with Kernel Density analysis to quantify individual space use. Home and core range areas were calculated, and sex-specific and spatio-temporal interactions were analyzed with overlap matrices. This research will equip managers with relevant information on the relationships between space use and behaviors of white sturgeon in this reservoir. The results provide areas of potential interest to further address habit complexity, fine-scale space use, and recruitment to further study spawning, foraging, and refuge-seeking behaviors in order to continue the conservation of white sturgeon
Point-particle modeling of sand dynamics in the nearshore sediment transport regime
No full textIn this dissertation, the ability of a point-particle model to accurately capture the dynamics of sediment-like particles in turbulence is evaluated and the settling dynamics of these particles is studied in direct numerical simulations (DNS). The model is then applied in a large eddy simulation (LES) to study the transient response of a flat polydisperse sediment bed to a developing oscillatory flow. This represents a complex regime relying on the accuracy of particle-flow interactions as well as particle collision dynamics in the densely packed near-bed region.
In point-particle modeling of sediment-like particles, it is crucial to couple the fluid and particle phases in an accurate way. This coupling comes down to a choice of the interpolation kernel responsible for interpolating fluid properties to the particle location to be used in force closures, as well to distribute a reactionary force from the particles back to the flow. A detailed grid refinement study examining fluid and particle statistics for grid-size particles in decaying homogeneous isotropic turbulence has been performed using DNS. It is identified that for these larger particles, implementing an interpolation kernel which is a function of the particle size, rather than the classically used grid-size dependent kernels, results in both fluid and particle statistics which remain converged under grid refinement. This ensures that the region of influences for particles do not change due to grid resolution. Furthermore, the best size of this filter, which strikes a balance between computational efficiency and accuracy, is determined by comparing results to particle-resolved simulations under the same conditions.
Next, the fundamental settling dynamics of sediment-like particles in turbulence is examined through a parametric investigation, covering a range of Stokes numbers and turbulence intensities. Nearshore sediment transport directly depends on the settling dynamics of sediment in a turbulent boundary layer, so improving the picture of fundamental settling dynamics in turbulence could eventually lead to improved sediment transport parameterizations. In this work, it is identified that low and moderate Stokes number particles tend to experience enhanced settling speeds, relative to their still-water terminal settling speed, due to turbulence. This enhancement is found to be as high as 35\% in the range tested, which could significantly alter oscillatory flow transport dynamics such as the phase lag effect. Conversely, it is found that large Stokes number particles only experience a reduction in mean settling speed due to turbulence, by up to 30\% in the range tested. The physical mechanisms behind these settling dynamics are identified and a multiscale analysis revealed that enhanced settling speed is due to particles interacting with eddies roughly 5--10 times their size.
The full point-particle model, combined with a soft-sphere collision model, is finally applied to the case of a developing oscillatory flow over a polydisperse sediment bed. The transient response of a sediment bed to an evolving oscillatory flow is not extensively known, least of all in grain-scale simulations. In a fully developed sheet flow, the boundary layer is turbulent and the bed shear stress is large, allowing the bed to be broken up and particles resuspended during every flow acceleration phase. Before the boundary layer has fully developed, however, there is a fight between the weaker vortical structures at the bed, the gravitational forces on the bed itself, and collisional dissipation due to the dense packing. Additionally, with a polydisperse sediment bed, small expansion in the upper layers of the bed during flow acceleration quickly result in a coarse-over-fine grain size sorting which further increases the barrier for mobilization of the bed. In order to break the bed armoring and suspend sediment significantly, the vortices generated at the bed must become stronger and separate from the bed, triggering the turbulent boundary layer development. The early stages of this dynamic evolution are examined here using the point-particle model within a LES
Biocompatibility of Biomimetic and Natural Interfaces
No full textThis study examines the hematological effects of both engineered and naturally occurring interphases to assess the health risks associated with foreign surface exposure. We investigated how blood proteins and cells activate upon contact with these materials, potentially initiating thrombus formation via intrinsic and common coagulation pathways, and through platelet adhesion and activation. Focusing on a bioinspired slippery liquid-infused porous surface (SLIPS) and tampon-derived nanoparticles (NPs), we evaluated their thrombogenic potential through the activation of the intrinsic pathway zymogen Factor XII, the common pathway enzyme thrombin, and platelet adhesion and activation. It was hypothesized that engineered surfaces would enhance biocompatibility due to their omniphobic properties, whereas naturally occurring surfaces might not be hematologically passive. Our findings indicate that SLIPS surfaces increased FXII activation twofold compared to clinical-grade surfaces, although platelet adhesion, activation, and thrombin concentrations were similar to those observed on clinical-grade surfaces. Conversely, tampon-derived NPs increased FXII activation up to sixfold and reduced thrombin-antithrombin III complex formation by up to 40% compared to baseline. These results highlight significant differences in biocompatibility between engineered and natural interphases, suggesting that the surface chemistry and composition of biomaterials play a critical role in their interaction with blood components. Future research should explore how these interactions affect long-term health outcomes and guide the development of safer medical devices.KEYWORDS: Coagulation, Hemocompatibility, Biomaterials, Nanoparticle
Transitory
No full textTransitory unfolds as a lyric memoir that employs hybrid storytelling to explore one person’s journey through trauma, memory, and self-expression via art.
The collection begins with “The 11th Hour,” where the narrator engages in a charged conversation with her aunt while her estranged mother lies dying in the hospital. This opening scene anchors the emotional stakes and sets the tone for the narrative’s layered exploration of loss and reconciliation.
The section titled “Linoleum” opens the collection with a series of first-person vignettes that capture pivotal childhood memories. These snapshots gradually reveal the trauma that ultimately leads to the narrator’s estrangement from her mother.
Following “Linoleum” are the poems “Incoming” and “Seasons,” along with the short story “Portrait of a Child.” These works serve as narrative bridges, guiding the reader across shifting time periods and preparing them for the emotional and thematic progression of the collection.
In “Backslide and the Space Between,” the narrator enters young adulthood. This section deepens the exploration of the adults who shaped her life, culminating in a letter from her estranged mother—a moment that underscores the complexity of familial relationships.
The short story “In Quotation” adopts a second-person point of view and a more experimental form, using titled segments to frame the action. Through this less conventional style, the rebellious side of the narrator emerges, setting the stage for “Time Bomb,” a narrative essay that recounts the lived experience of coexisting with someone grappling with mental illness and substance abuse.
Together, these works form a creative nonfiction collection that experiments with narrative form and voice. Blending poetry, memoir, and fiction, the collection reimagines narrative form and invites readers to rethink how voice, structure, and technique shape personal histories
Disturbance, Season of Recruitment, Competition and Herbivory Effects on Ragwort Populations
No full textData from a field experiment examining the effects of season of disturbance (tilled soil in Fall 1986, Spring 1987), 3 levels of interspecific plant competition (other vegetation Removed, Clipped, or Unaltered) and exposure to two biological control agents (ragwort flea beetle, cinnabar moth) on tansy ragwort (Senecio jacobaea, syn. Jacobaea vulgaris) populations at Cascade Head Scenic Research Area on the Oregon coast, from 1986-09-05 through July 1990. Data on ragwort populations in experimental subplots (0.0625 m2) and plots (0.25 m2) includes: 1) julian day (day of year) of emergence, first incidence of herbivory, and death; 2) number of flowering plants and capitula; 3) number of new ragwort juveniles established in 1989; 4) percent cover of ragwort, other plant species, litter and bare ground; and 5) dry biomass of ragwort
Learning parameters of differential equations through statistical inference and computational algorithms
No full textThis thesis develops a clear and accessible framework for integrating mathematics, statistics, and computer science in order to estimate unknown parameters of differential equations from noisy data. As a case study, we focus on the exponential growth equation, a simple yet widely applicable model. The mathematical foundation defines the governing equation, the statistical framework accounts for observational noise through Maximum Likelihood Estimation (MLE) and Fisher information, and computational algorithms implement the optimization and visualization. Numerical experiments confirm that this interdisciplinary workflow can accurately recover parameters from limited and noisy observations. The study highlights how mathematical structure, statistical reasoning, and computational tools form a coherent whole that is pedagogically valuable and practically reproducible
Bio-cementation for protection of coastal dunes : physical models, element tests, and numerical simulation
No full textCoastal dunes are natural protective barriers, shielding coastal communities and vital infrastructure from flooding, particularly during severe storms. To effectively safeguard inland areas, these dunes must withstand erosion in the face of such events. However, the accumulation of wave-induced pore water pressure within sandy soil can lead to localized regions of liquefaction, allowing soil particles to detach, and thus, facilitating erosion, ultimately causing failure. The intentional alignment of natural and engineering processes, known as engineering with nature (EWN), aims to seek sustainable solutions to reduce the effects of extreme events on the morphology of coastal regions. EWN includes development and implementation of natural and nature-based features (NNBF) as solutions to restore and protect beaches.
Microbial induced carbonate precipitation (MICP, or more colloquially, bio-cementation) presents a promising method to enhance the shear strength of sand and counteract erosion. It can be used to increase the critical shear strength of sand and mitigate erosion. In an effort to introduce bio-cemented dunes as an appropriate NNBF for coastal risk mitigation, this research has investigated the efficacy of MICP for reducing the impact of extreme events on dune erosion resistance. For this purpose, two near-prototype-scale experiments with different levels of cementation were performed. In the experiment, a model sand dune was constructed in the large wave flume (104 m × 3.7 m × 4.6 m, L×W×D) at the O.H. Hinsdale Wave Research Laboratory. Uncemented and bio-cemented dunes were subjected to 25 trials of approximately 300 waves each, with varying wave characteristics such as water depth, wave height, and wave period. The wave characteristics were the parameters matched to the scaled Hurricane Sandy. Remote sensing technology was used to assess the efficacy of the treated dunes during the simulated storm surges. For this purpose, three-dimensional scanners were employed to capture the dune profile's evolution between wave trials. Dunes were scanned prior to the first trial to develop a baseline for monitoring erosion in subsequent trials. Dune scarp and morphological development in treated and untreated zones were used to evaluate the performance of the bio-cemented dunes under wave loading. In addition to using remote sensing to assess the efficacy of the treated dunes during the simulated storm surges, a series of laboratory element tests was conducted on cores taken from the surface crust after the storm simulation. Laboratory test results demonstrated that increases in cementation level leads to stiffness and shear strength improvement of sand.
A new two-dimensional numerical model was developed to simulate a sand profile subjected to repeated wave loading to investigate the wave-induced pore pressure regime in the soil. Oscillatory and residual soil responses are the causes of excess pore pressure generation in the soil during storms. The oscillatory pore pressure is due to the fluctuation of the water level above the seabed under wave loading and can cause momentary liquefaction. Due to wave-induced cyclic shear stress, the principal stress orientation rotates continuously and can accelerate plastic deformations, causing an accumulation of residual pore pressure. This work used a system of equilibrium and continuity equations, including a source term, to form the governing framework for predicting the residual and oscillatory components of pore water pressure due to repeated wave loading. The model was developed such that it can support the simulation of bio-mediated soil improvement techniques used to improve the shear strength and stiffness of soil through direct modification of physically meaningful material parameters. This study incorporated the constitutive properties of bio-cemented sand to capture the pore pressure response within the treated soil. The numerical results indicate that the bio-treated layer decreases the upward pore pressure gradient in the susceptible region close to the ground surface. Moreover, due to shear strength improvement, the rate of pore pressure generation in treated soil is significantly lower than in untreated soil