Physical Sciences and Mathematics Commons^™

A Projector-Rank Partition Theorem For Exact Degrees Of Freedom In Experimental Design, K. G. Nagananda

Mathematics and Statistics Faculty Publications and Presentations

In many experimental designs—split-plots, blocked or nested layouts, fractional factorials, and studies with missing or unequal replication—standard ANOVA procedures no longer tell us exactly how many independent pieces of information each effect truly contributes. We provide a general degrees of freedom (df) partition theorem that resolves this ambiguity. For N observations, we show that the total information in the data (i.e., N −1 df) can be split exactly across experimental effects and randomization strata by projecting the data onto each stratum and counting the df each effect contributes there. This yields integer df—not approximations—for any mix of fixed and random …

Xenoliths In Meteorites: Insights Into The Dynamics Of Material Exchange Between Asteroids, J. Gattacceca, B. Devouard, L. Bonal, Y. Marrocchi, A. Greshake, R. Tartese, M. Gounelle, D. Auyang, C. Sonzogni, M. Hutson, Multiple Additional Authors

School of Earth, Environment, and Society Faculty Publications and Presentations

A minor fraction of meteorites contains xenoliths, that is, clasts that were formed on a different parent body than that of the host lithology. The occurrence of xenoliths is direct evidence for the exchange of material between asteroids, including exchanges between asteroids from the carbonaceous (CC) and non-carbonaceous (NC) reservoirs. Overall xenolith population statistics may therefore inform us about the dynamical mixing of these two asteroid reservoirs. Xenoliths are also intrinsically interesting because they may sample parent bodies that are not represented in the meteorite collection. In this work, we conducted a critical and exhaustive review of xenoliths described in …

Measurements And Analysis Of Light Non-Methane Hydrocarbon Mole Fractions In 1982–1987 At Six Remote Sites Along The Pacific Rim, A. M. Smith, C. L. Butenhoff, M. A. K. Khalil, A. L. Rice

Physics Faculty Publications and Presentations

Atmospheric non‐methane hydrocarbons (NMHCs) are important trace species with anthropogenic and natural sources including fugitive emissions from fossil fuel mining and distribution, biomass burning, biofuel combustion, and biogenic emissions from microbes and plants. We present previously unpublished whole air sample measurements of NMHCs collected at approximately weekly intervals from 1982 to 1987 at six stations spanning the Northern and Southern hemispheres, which sampled primarily Pacific Basin air masses as determined by back‐trajectory analysis. The four alkanes in this data set, ethane, propane, i‐ and n‐butane had a mean measured mole fraction of 712 ± 22 ppt, 245 ± 13 ppt, …

Extensive Glacier Loss In The Coterminous United States, Andrew G. Fountain, Bryce Glenn, Christopher Mcneil, Brian Menounos

Geology Faculty Publications and Presentations

Glaciers populate the mountain ranges of the western conterminous United States and despite their importance to alpine hydrology, their area and volume change have never been comprehensively evaluated. Our study shows that since the mid-twentieth century about one-quarter of the glaciers have disappeared and the overall area and volume are reduced by one-third. The pattern of glacier shrinkage suggests most glaciers in the conterminous United States are largely maintained by local topographic influences due to their small size. These results improve our understanding of evolving high alpine hydrology and importance to ecosystem processes.

Computational Study Of Irrational Rotations Via Exact Discontinuity Tracking: A New Experimental Framework, Hannah Kravitz

Mathematics and Statistics Faculty Publications and Presentations

We present an algorithm for studying the sum𝐺𝑁⁡(𝑥,𝜌)=𝑁∑𝑘=1[{𝑥+𝑘⁢𝜌}−12],

which is closely related to the discrepancy of the irrational rotation. Computation of𝐺𝑁and associated statistics is notoriously difficult due to numerical instability and the failure of sampling to capture the discontinuities. Our algorithm instead fully defines𝐺𝑁through its discontinuities, which allows computation of𝐺𝑁⁡(𝑥,𝜌)with errors on the order of𝑁times machine epsilon in𝑂⁡(𝑁)time for practical𝑁. The associated probability density function can then be computed in𝑂⁡(𝑁⁢log⁡𝑁)time. Presented as a tool for experimental mathematics, the algorithm enables reliable plots of the descriptive statistics of𝐺𝑁over𝑁, in particular the length of the support of the pdf (the discrepancy), revealing …

Don’T Sweat Interaction Trees Proof-Guided Local Variable Lifting For Interaction Trees, Yiming Lin, Ian Kariniemi, Yao Li

Computer Science Faculty Publications and Presentations

Verifying existing software is hard: Programs are developed in languages not amenable to verification, involve complicated optimizations that obscure the underlying logic, and are gigantic in size. In this paper, we propose a way to ease this pain via a simplification framework that employs interaction trees as a language-agnostic interface. We show that local variable lifting, the technique underlying AutoCorres for the Simpl language, can be generalized to interaction trees via an implementation in Rocq. A key challenge with simplifying interaction trees is that they are highly dynamic structures and we would like our approach to work with mostly uninterpreted …

Representation Stability In The Intrinsic Hyperplane Arrangements Associated To Irreducible Representations Of The Symmetric Groups, Ian Flynn, Eric Ramos, Benjamin Young

Mathematics and Statistics Faculty Publications and Presentations

Some of the most classically relevant Hyperplane arrangements are the Braid Arrangements Bn and their associated compliment spaces Fn. In their recent work, Tsilevich, Vershik, and Yuzvinsky [TVY20] construct what they refer to as the intrinsic hyperplane arrangement within any irreducible representation of the symmetric group that generalize the classical braid arrangements. Through examples it is also shown that the associated compliment spaces to these intrinsic arrangements display behaviors far removed from Fn. In this work we study the intrinsic hyperplane arrangements of irreducible representations of the symmetric group from the perspective of representation stability. This work is both theoretical, …

Factors Influencing Non-Perennial Stream Initiation In The Mt. Hood National Forest, Allison Bast

Dissertations and Theses

Historically, non-perennial headwater streams have been overlooked due to their small size and infrequent flow regimes, often leading to them not being recognized as legitimate streams, despite scientific evidence that has shown these streams significantly affect the quality of downstream waters. To combat this issue, environmental managers need to be able to accurately identify and delineate the origins of these streams; however, despite decades of research, an accurate, universal method for predicting how and where these streams commence has yet to be developed. Early studies conducted in steep, humid environments, identified a strong inverse linear relationship between the size of …

A Systematic Approach For Controlling Tem Sample Thicknesses, Monte Kozell

Physics Faculty Publications and Presentations

Historically, TEM prep has been an artisan craft without a systematic workflow that ensures quantified control over TEM sample thickness. Over- and under-thinning is a significant problem in the TEM prep process. A direct measurement process was demonstrated to control the final thickness of the TEM lamella. Final lamella thickness was controlled by directly measuring lamella thickness in real time using a 10–15 kV SEM while performing secondary electron imaging at the mill position, allowing for (human-mediated) closed-loop processing. We demonstrated the utility of this technique by systematically thinning five TEM samples to discretely target thicknesses ranging from 100 nm …

Epidemic Dynamics Under Pulse Population Exchange, Hannah Kravitz, Christina Durón, Moysey Brio

Mathematics and Statistics Faculty Publications and Presentations

Many epidemiological models assume either closed populations or continuous demographic turnover. We consider an intermediate setting in which exchange occurs through discrete pulses. In this paper, we introduce a population-conserving compartmental epidemiological model with pulse population exchange at a set of prescribed times. At each pulse, a fraction of the population in each compartment is replaced by a combination of susceptible and immunized individuals. In contrast to typical pulse birth or pulse vaccination models where only a single compartment undergoes a pulse population change, the pulses in this model have competing effects: removing infectious individuals reduces the force of infection, …

Catching A Glimpse Of Complex Relaxation: A Theoretical Phase Transition Is Finally Experimentally Observed In A Material, Yogesh Joglekar

Physics Faculty Publications and Presentations

A bulk crystal, as small as 0.5 mm in size, contains more than a quintillion atoms that behave collectively like a large-scale object. When such a crystal is disturbed by an outside influence, it quickly transitions into a new steady state after a brief transient phase known as relaxation. When this phase is the shortest in duration, the system can exhibit extreme sensitivity to even a tiny perturbation. Examining changes in relaxation in a bulk material could help engineer new sensors and rapid response devices. However, the transient response only lasts for a few picoseconds, making observation difficult. On page …

Representing Post-Fire Reality: An Empirically Informed Temperature Index Approach To Post-Fire Hydrologic Modeling In Oregon's Western Cascades, Logan Hastings

Dissertations and Theses

The invaluable water resources stored in snowpack face mounting threats from rising temperatures, drought, shifts in precipitation regimes, and increased fire frequency, which pose challenges to operational hydrologic modeling in Oregon's sensitive maritime snowpacks. The gridded temperature index (GTI) approach in operational models like the Hydrological Engineering Center's Hydrologic Modeling System (HEC-HMS) from the U.S. Army Corps of Engineers remains in common use for its minimal data requirements, but how GTI parameterizations should adapt to post-fire conditions is largely unknown.

This research assessed the impact of the 2020 Lionshead Fire on HEC-HMS performance in the North Santiam River basin across …

Evolution Of Global Sea‐Level Rise Projections And Their Uncertainty, Andra J. Garner, Amy Appollina, Jessica Slotter, Gregory G. Garner, Aimée B. A. Slangen, Robert E. Kopp, Benjamin P. Horton

School of Earth, Environment, and Society Faculty Publications and Presentations

For more than 40 years, scientists have projected future sea‐level change. Documenting how sea‐level projections have evolved is vital for tracking progress, uncertainties, and future research needs. Here, we update and analyze a database of global‐mean sea level (GMSL) projections dating from 1982 to 2025, identifying five key findings. First, GMSL projection generation has been concentrated in a small number of developed countries, with 95% of projections produced in the United States, United Kingdom, European Union, or Australia. Second, while GMSL projections for 2050 and 2100 have been published regularly since the early 1980s, only 30 of 103 studies have …

Oregon State Rank Assessment For Schweinitz's Cyperus (Cyperus Schweinitzii), Nora Dunkirk

Institute for Natural Resources Publications

Oregon state conservation status assessment for Schweinitz's cyperus (Cyperus schweinitzii) using NatureServe methodology, 2026.

Oregon State Rank Assessment For Koehler's Rockcress (Boechera Koehleri), Lindsey K. Wise, Gabriel Campbell

Institute for Natural Resources Publications

Oregon state conservation status assessment for Koehler's rockcress (Boechera koehleri) using NatureServe methodology, 2026.

Feedback Indices To Evaluate Llm Responses To Rebuttals For Multiple Choice Type Questions, Justin C. Dunlap, Anne-Simone Parent, Ralf Widenhorn

Physics Faculty Publications and Presentations

We present a set of indices designed to characterize Large Language Model (LLM) responses when challenged with rebuttals during a chat. Assessing how LLMs respond to user dissent is crucial for understanding their reliability and behavior patterns, yet the complexity of human-LLM interactions makes systematic evaluation challenging. Our approach employs a fictitious-response rebuttal method that quantifies LLM behavior when presented with multiple-choice questions followed by deliberate challenges to their fictitious previous response. The indices are specifically designed to detect and measure what could be characterized as sycophantic behavior (excessive agreement with user challenges) or stubborn responses (rigid adherence to the …

Developing Field And Spaceflight Microscopy, Nikki Johnston

Dissertations and Theses

Designing for spaceflight favors the reduction of unnecessary features and cost-cutting, whether thisbe computation, hardware, or procedure. Resources are spent toward fortification and mission success over convenience. Such design goals paired with the relatively smaller budgets of academia lead us to do as much as we can in-house and use open-source as much as we can without compromising mission success. We also believe that thoroughly testing technology in extreme environments on earth is necessary for the success of a flight instrument. We focus on microscopy for life detection. I have spent my time here learning methods of hand-building microscopes to …

Oregon State Rank Assessment For Stemmed Polypore (Xeroceps Skamania), Nora Dunkirk

Institute for Natural Resources Publications

Oregon state conservation status assessment for Stemmed Polypore (Xeroceps skamania) using NatureServe methodology, 2026.

Surface Co-Crystallization With An Organic Single Crystal Enables Vapochromic And Luminescent Detection Of Phenols, Ivan Bondarenko, Kaleb Hood, Elani J. Cabrera-Vega, Aminata Dioume, Alaric Shaw, Josephine Bicknell, Simon J. Teat, Nicholas S. Settineri, Andrea M. Goforth, Stephanie S. Lee, Jun Jiao, Gonzalo Campillo-Alvarado

Chemistry Faculty Publications and Presentations

We present a novel approach for the vapochromic and luminescent detection of phenols through surface co-crystallization with single crystals of 9,10-bis(()-2-(pyridin-4-yl)vinyl)anthracene BP4VA. Upon exposure to 2,4,6-trifluorophenol (2,4,6-TFP), 3,4,5-trifluorophenol (3,4,5-TFP), and phenol (PhOH) vapor, BP4VA crystals exhibit significant changes in color and fluorescence intensity, offering a sensitive detection method. Detailed structural insights into intermolecular interactions are obtained from single-crystal and powder X-ray diffraction, as well as FT-IR and H NMR spectroscopies. Scanning electron microscopy and energy dispersive X-ray spectroscopy demonstrate the reversibility of these changes, with crystal morphology and surface composition nearly returning to near-pristine single crystals of BP4VA after annealing. …

Multi-Ion Permeation And Dynamic Conductance Modulation In Connexin Gap Junction Channels, Bassam G. Haddad, Daniel M. Zuckerman, Steve L. Reichow

Chemistry Faculty Publications and Presentations

Gap junction channels formed by connexins mediate direct intercellular communication and are essential for electrical signaling and tissue homeostasis. Despite their large, solvent-accessible pores, connexin channels exhibit distinct conductance, selectivity, and rectification properties, but the molecular mechanisms underlying these behaviors remain incompletely understood. Here, we performed ~67 μs of all-atom computational electrophysiology simulations of connexin-46 (Cx46), connexin-50 (Cx50), and heterotypic Cx46/50 gap junction channels based on high-resolution open-state structures, enabling characterization of both ion permeation and long-timescale channel dynamics. Simulations reveal a multi-ion, multi-pathway permeation mechanism governed by isoform-specific energetic barriers and transient ion coordination sites that shape conductance and …

Temperature And Hydrologic Context Influence Methane Variability In A Low-Salinity Marsh, Zoie Brauser

Dissertations and Theses

Coastal wetlands are biogeochemical hotspots that capture and transform carbon and nutrients. Wetland restoration is increasingly used as a climate mitigation strategy because of wetlands' capacity to sequester large amounts of carbon. However, low-salinity tidal marshes exhibit high variability in methane (CH₄) emissions, which could partially offset carbon sequestration under certain conditions. Understanding the drivers of CH₄ variability is crucial for restoration and conservation work. This project uses an observational research approach to assess the relationships between environmental factors and carbon dioxide (CO₂) and CH₄ soil gas fluxes in a restored low-salinity tidal marsh …

Set-Valued Conjugate Calculus And Duality In Optimization And Machine Learning Via Generalized Relative Interiors, Gary Lee Sandine

Dissertations and Theses

Convex analysis, optimization, and duality theory are broadly applicable to a multitude of real-world problems. Theoretical frameworks ensuring strong duality and optimality are fundamentally tied to convex separation under qualification conditions frequently involving topological or relative interiors. These can be empty in convex sets that appear naturally in infinite-dimensional models, yet guarantees of optimality and strong duality are often attainable. This dissertation presents frameworks for applying convex separation via generalized relative interiors to develop generalized calculus rules as well as conditions for strong duality and optimality for infinite-dimensional constrained convex optimization problems.

The first major contribution is the introduction of …

Oregon State Rank Assessment For Deer-Cabbage (Nephrophyllidium Crista-Galli), Lindsey K. Wise

Institute for Natural Resources Publications

Oregon state conservation status assessment for Deer-cabbage (Nephrophyllidium crista-galli) using NatureServe methodology, 2026.

Moss Biomonitoring And Isotopic Signatures Reveal Aviation Fuel As Local Lead Source Near Oregon Airports, Oluwaseyi E. Aderinboye, Alyssa E. Shiel, Lauren Stalford, Christina J. Murphy, Dean B. Atkinson

Chemistry Faculty Publications and Presentations

Lead emissions from piston-engine aircraft using leaded aviation gasoline (avgas) remain a significant source of environmental contamination near regional airports, posing potential health risks to nearby communities. Passive biomonitoring using the epiphytic moss Orthotrichum lyellii was combined with lead isotope fingerprinting to quantify lead concentrations and distinguish between legacy leaded gasoline and current avgas emissions near Hillsboro and Troutdale airports in Oregon. Here we show that lead levels are elevated by up to 50 times the rural background near airports, with isotopic signatures confirming avgas as a dominant local source. These findings indicate that avgas use contributes substantially to environmental …

Lessons From The Club Homeschool Capstone: Testing, Data Discipline, And The Computer Science Curriculum, Shane Brown

University Honors Theses

This thesis looks at the CLUB Homeschool Capstone project to argue that Portland State University's Computer Science curriculum should introduce testing and data quality discipline earlier and more intentionally than it does now. As team lead of a seven-person team, I coordinated sprint planning, communicated with the sponsor, and developed custom Discourse plugins that enhanced an existing forum platform instead of creating a separate application database, as requested by the sponsor. The project's requirements document called for a formal testing plan, but our team lacked the practical experience to implement one. This gap became evident through my internships as a …

Oregon State Rank Assessment For Alpine Smelowskia (Smelowskia Ovalis), Lindsey K. Wise

Institute for Natural Resources Publications

Oregon state conservation status assessment for Alpine smelowskia (Smelowskia ovalis) using NatureServe methodology, 2026.

Oregon State Rank Assessment For Ithuriel's Spear (Triteleia Laxa), Lindsey K. Wise

Institute for Natural Resources Publications

Oregon state conservation status assessment for Ithuriel's spear (Triteleia laxa)
 using NatureServe methodology, 2026.

Editorial: Participatory And Just Governance: Empowering Local And Indigenous Communities, Melissa Haeffner, Maiko Sakamoto, Jenia Mukherjee, Hong Quan Nguyen, Soyo Takahashi

Environmental Science and Management Faculty Publications and Presentations

The papers in this Research Topic (RT) extend insights on the roles of social relations, institutional arrangements, Indigenous ways of knowing, local knowledge, and decisionmaking participation in shaping water governance and practice. Despite efforts to predict flows and possible hazards, we continue to observe “unintended consequences” when humans interact with waterscapes. What we often learn, we argue, is that what appears “unintended” often reflects a deliberate architecture of exclusion; one that becomes legible only when social power relations are placed at the center of analysis alongside hydrological variables. Doing so may illuminate where injustice complicates intentions and what difference participatory …

Oregon State Rank Assessment For Thompson Mistmaiden (Romanzoffia Thompsonii), Nora Dunkirk, Gabriel Campbell, Sue Vrilakas

Institute for Natural Resources Publications

Oregon state conservation status assessment for Thompson mistmaiden (Romanzoffia thompsonii) using NatureServe methodology, 2026.

Oregon State Rank Assessment For California Pinefoot (Pityopus Californicus), Lindsey K. Wise

Institute for Natural Resources Publications

Oregon state conservation status assessment for California Pinefoot (Pityopus californicus) using NatureServe methodology, 2026.