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ENERGY DENSITY OF AMPELISCID AMPHIPOD POPULATIONS PREYED UPON BY GRAY WHALES IN THE NORTHERN BERING AND CHUKCHI SEAS
No full textThe shallow and highly productive waters of the northern Bering and Chukchi Seas in the Pacific sector of the Arctic are able to support numerous upper trophic level predators, including benthic feeders such as the gray whale (Eschrichtius robustus). The Eastern North Pacific population, currently the largest population of the species, migrates thousands of kilometers from calving lagoons in Baja California, Mexico to Arctic foraging grounds to feed on numerous kinds of marine invertebrates. Historically, their primary source of food has been benthic ampeliscid amphipods (Family Ampeliscidae), which can form large, dense mats of tubes in sandy sediments on the seafloor. However, several studies have noted a decline in the biomass of these amphipods since the 1980s, particularly in the Chirikov Basin just south of Bering Strait,where they are the most abundant. Concurrently with this trend, gray whales have experienced two major Unusual Mortality Events (1999-2000 and 2019-2023), as defined by NOAA; observations of emaciated whales during these events have called into question the quality and availability of benthic amphipods as prey for gray whales and their ability to support the gray whale population. To address these questions, the caloric contents of several of the most abundant benthic amphipod genera in this region were measured and compared to similar measurements published in studies going back as far as 1978. As part of this study, a conversion factor between frozen and formalin-preserved amphipod specimens was developed and applied to a time series of amphipod abundance and biomass (1970-2019) to better quantify how energy
density of benthic amphipod communities has changed over time. The energetic content of these amphipods has not changed significantly from historical values, but the amount of biomass per square meter of seafloor available has declined drastically. For ampeliscid amphipods in the Chirikov Basin, the maximum mean energy density was 347.08 kJ m^-2
in 1984; the minimum mean energy density was 31.07 kJ m^-2 in 2010, a 90% decline over 26 years. These findings suggest that, while benthic amphipods are still a high-quality food source, the extensive and dense sources of energy they once provided are no longer available. In response, gray whales are venturing further north in search of prey, bypassing formerly sufficient foraging grounds.
Two supplementary (S) files of data sets are included with this thesis project, along with descriptions of each of the variables used in the dataset. File S1 consists of all the caloric measurements made for Chapter 2. File S2 is the compiled time series synthesized for Chapter 3. Some variables in the time series dataset (S2) are calculated from values in the Chapter 2 caloric data
Comparing the Effectiveness of Standard vs. Multilevel Machine Learning Algorithms on Hierarchical Data
No full textThis dissertation explored the performance of standard and multilevel machine learning classification algorithms on hierarchical datasets, which are prevalent in educational research due to multistage sampling techniques (e.g., students nested within schools). Hierarchical data pose unique analytical challenges (e.g., nonindependence of data), often requiring specialized approaches. While multilevel modeling is well-established in inferential contexts, its potential in predictive scenarios had been largely underexplored.
Through a Monte Carlo simulation and empirical analyses using data from the Maryland Longitudinal Data System (MLDS), this study evaluated the suitability of standard and multilevel algorithms. Results revealed that multilevel models offered slight advantages in high residual level-2 variance settings, effectively capturing cluster-level dependencies and providing stable predictions. Standard models performed well in low residual level-2 variance contexts, while standard models incorporating cluster IDs as fixed effects performed comparably to multilevel models under many conditions, including high residual level-2 variance scenarios. However, this approach was only feasible when training and testing clusters overlapped, highlighting limitations in generalizing predictions to unseen clusters. In an empirical analysis addressing class imbalance, Logistic Regression and GLMM exhibited the highest sensitivity for identifying STEM completers when training and testing clusters overlapped while Neural Nets and XGBoost demonstrated better performance in identifying the minority class when training and testing clusters were distinct. These findings highlighted the complexity of predictive modeling for hierarchical data and provided insights for prediction tasks in educational research
PALS 2025 : Deliverable 4
No full textThis presentation displays the details and documentation of the Blooms and Beats Block Party in the UMD PAL 2025 Green Isles Project.Acknowledgements: School of Architecture and Urban Planning, Creative Placemaking Minor, PALS (Partnership for Action Learning in Sustainability), Purple Line Corridor Coalition, Takoma Langley Crossroads Development Authorityhttps://drive.google.com/file/d/1_tN5j51SZ3_T3KcJTwGbQQu25_498-F6/view?usp=sharin
The Effect of Inorganic-Organic Physicochemical Properties on CCN Activity of Complex Mixtures
No full textAerosol effects on Earth’s climate are a major source of uncertainty in predictions of radiative forcing. The physical and chemical composition of aerosols modify cloud reflectivity and lifetime, which exert a strong, but uncertain, cooling effect on the climate; this indirect effect is attributed to aerosols’ ability to form cloud condensation nuclei (CCN). Aerosol particles are often mixtures of inorganic and organic components, and their composition impacts their water-uptake, hygroscopicity and droplet formation. Atmospheric organic aerosol have a wide range of thermodynamic physicochemical properties, therefore introducing complexity in hygroscopicity and droplet formation predictions. To shed light on complex aerosols, this thesis uses laboratory based measurements and characterization techniques to elucidate organic physicochemical property effects on aerosol water uptake. Results of this work will better inform current hygroscopicity models. One such property is an organic compound’s ability to partition to the surface (hence, surface-activity). Organic partitioning can be enhanced during organic-inorganic interactions, known as salting out effects. The effects of salting-out and surface-active organic partitioning on water uptake of mixed organic-inorganic aerosols are investigated. Furthermore, we introduce new computationally efficient parameterizations for subsaturated and supersaturated droplet growth and CCN predictions. Results also show that both organic functional group and aerosol viscosity can also influence salting out and salting-in effects. Specifically, these properties can be predicted and influence the presence of liquid-liquid phase separation (LLPS) and subsequent aerosol water uptake processes. This work finds that organic functional groups, especially for nitrogen containing species, drive interactions with inorganic components; these interactions result in experimental water uptake that deviates from traditionally used hygroscopicity models. Therefore, organic functional groups and internal aerosol phase morphology are critical to improving our scientific understanding of aerosol-climate effects
Evaluating Costs, Quality and Performance within a Market Economy Framework for the Nations of the Organization for Economic Cooperation and Development (OECD)
No full textTitle of Dissertation: Evaluating Costs, Quality and Performance within a Market Economy Framework for the Nations of the Organization for Economic Cooperation and Development (OECD)
Joshua Winer, MPH, MBA, Doctor of Philosophy, 2024
Dissertation Directed By: Jie Chen, PhD
Department of Health Policy Management
Background: National healthcare delivery systems and social determinants of a population coexist within the confines of capitalism. But not all capitalist economies behave the same way. Two poles exist that demarcate the degree to which that national economy engages in coordination or liberal competition. The 38 member nations of the Organization for Economic Cooperation and Development (OECD) represent democratic governments with market-based economies. COVID-19 demonstrated that nations with Coordinated Market Economies (CME) fared better in both economic (national GDP and labor productivity measures) and health outcomes (case positivity rates and deaths) than Liberal Market Economies (LMEs). The distinguishing trait of the CME is the degree to which protection is afforded to the individual via social policy and normative values. Social and welfare markets are critical and more prevalent within CMEs. Creation of a CME order is predicated on growth of human capital stock whereas LMEs coordinate via hierarchies, competitive markets and market incentives. The current practice of evaluating differences in healthcare costs across nations utilizes the GINI coefficient and market income (i.e., total national income before debts and taxes) as independent variables. . This new approach will endeavor to create a Coordination Index across values of economic equality, education, political institutions, market concentration and employment stability. This new approach evaluates whether the OECD nations based on their level of coordination (i.e. CME vs. LME traits) produce significant differences via the Triple Aim framework: cost, care quality, and system performance by using the Coordination Index to assess cost on a total per capita expenditures basis; quality through life expectancy of the total population, and system performance via avoidable mortality.Data and Methods: A conceptual framework was first designed to explain the synergies across Andersen’s Behavioral Model, Lorenzoni and Belloni’s Reciprocal Domains, Hall and Soskice’s Coordinated Markets, and with support from Esping-Andersen and Gunnar Myrdal’s analyses on welfare states and Keynesian programs. A comprehensive literature review was conducted to make the case for inclusion of these frameworks and the differing traits they offer if collated into a novel data index. Finally, I tested the model and hypotheses empirically. Data comes from the 38 OECD nations for the period of 2008 to 2018. Measures used to create the index included: GINI coefficient of the market income; Index of Economic Freedom; Freedom in the World Score; Labor Market Institutions Index; Strictness of Employment Protection; Social Progress Index; World Integrated Trade Solutions Market Concentration; and the OECD Database. I created the coordination index using the average measures of the aforementioned multidimension aspects of coordination using the datasets presented above. After which, I applied linear regression analyses to examine the association between Coordination Index and cost, quality, and system performance.
Results: I established a conceptual model delineating the components of market and national coordination that would in theory serve as material influences on healthcare cost, quality and system performance. The empirical findings were consistent with this theory. Coordination plays a significant part in healthcare cost, quality and system performance. The empirical findings were consistent with the theory. The new Coordination index further surpassed the benchmark of an Alpha score range of 0.65 to 0.7 indicating reliability of the measure. The Creation of a new Coordination Index on a z-scale (mean: 0, median: 0.133, minimum: -4.602, maximum: 2.531) explained a higher degree of variance and association in univariate regression with Total Health Expenditure: (coeff. 0.275, 0.263 adjusted R-squared, Standard Error 0.023, Root MSE 0.460, p < 0.001) compared to using GINI alone (coeff: -3.917, 0.131 adjusted R-squared, Standard Error 0.498, Root MSE 0.500, p<0.001). I further find that Coordination had a positive association and was significantly associated with higher total cost in a baseline model and when adjusted for insignificant findings and collinearity was still significant (coeff. 0.036, p<0.05). I also find that Results showed first that the mean difference between higher quartile rankings and lower quartiles of Coordination in regard to Total Health Expenditure is significant (p<0.01), and secondly that a statistically significant (p<0.01) difference exists amongst Total Health Expenditure by quartiles of Coordination. The findings indicate that changes in Market Coordination towards the mean distribution of the OECD are associated with a higher total expenditure of 0.036 on a natural log basis, or approximately $1.036 (in thousands) per year higher Total Expenditure. I also find that Coordination did have a positive association but not a statistically significant association with a natural log of Life Expectancy in a baseline model nor when adjusted for insignificant findings and collinearity (coeff. 0.002, p<0.05) in regression. I conclude however though first that the mean difference between quartile rankings of Coordination is significant for quartiles 1 and 4 (p<0.01) and quartiles 2 and 3 (p<0.01) in regard to Life Expectancy. Secondly, that a statistically significant (p<0.01) difference exists amongst variances by quartiles of Coordination for Life Expectancy. The findings indicate that changes in Market Coordination towards the mean distribution of the OECD is associated with an increase in mean Life Expectancy of 0.002 on a natural log scale, or nearly 1 year when converted. I use the metric of Avoidable Mortality as a measure for system performance and find that Coordination was negatively associated and statistically insignificant on an Avoidable Mortality per 10 000 scale in a baseline model nor when adjusted for insignificant findings and collinearity (coeff. 0.275, p<0.05) in regression. However, I do conclude first that the mean difference between higher quartile rankings and lower quartile rankings of Coordination with is significant (p-value: 0.000, p<0.01) for quartiles 2 and 3 as well as quartiles 1 and 4 (p-value: 0.000, p<0.01). Secondly, that a statistically significant (p<0.01) difference exists among variances by quartiles of Coordination for Avoidable Mortality. This finding indicates that changes in Market Coordination towards the mean distribution of the OECD are associated with a decrease in Avoidable Mortality of approximately 3 deaths per 100 000.
Conclusion: Within the OECD nations, changes in market Coordination towards the mean distribution of the OECD are significantly associated with, and have increases in healthcare cost, quality, and system performance. Quartile levels of Coordination are also shown to produce statistically significant differences in cost, quality and system performance as well, with higher levels of Coordination having lower cost, higher quality and better performance. Though slightly imperfect in its pursuits, Coordination as a concept advances the notion that the pursuit of a welfare state which places the values of economic equality, education, political institutions, market concentration and employment stability as priorities has a relationship to healthcare as an institution. Changes to these institutions and values should be made in harmonization with all other policy measures to achieve substantive gains. Failure to improve healthcare in conjunction with these other values risks enfeebled outcomes to the former
A LANDSCAPE FOR LEARNING AT THE CENTRAL MARYLAND RESEARCH AND EDUCATION CENTER HEADQUARTERS
No full textThis thesis explores the integration of sustainable landscape design principles to enhance research, education, environmental stewardship, and aesthetic improvements at the University of Maryland Extension (UME) Central Maryland Research and Education Center (CMREC) headquarters. As part of UME’s mission to provide research-based, practical education to communities, this project provides a thoughtful design that turns the landscape into an interactive teaching tool, reinforcing Extension’s commitment to education and outreach. The design aims to create a multifunctional landscape that supports ecological health, provides outdoor learning and research spaces, and improves both the function and aesthetics of the site. A research-based design approach was used, incorporating a literature review, case studies, site inventory and analysis, and stakeholder input to develop an informed and effective plan. Key design features include a teaching pavilion, trial research fields, accessible raised beds, and a meadow boardwalk, all of which contribute to a more engaging and sustainable environment. The proposed design is expected to serve as a point of pride for the University of Maryland community. With clear metrics in place to assess its success, this project serves as a replicable model for sustainable landscape design at other Extension program locations
CHARACTERIZATION OF CURRENT SPIN QUBIT DEVICES AND A PROPOSED NEW QUBIT DESIGN
No full textWe characterize the performance of current quantum dot spin qubit devices for small quantum simulations, demonstrate a new theoretical framework for the modeling of the qubit charge stability diagram, and propose a new qubit design to extend coherence times and reduce leakage errors in exchange qubits. First, we show that silicon quantum dot spin qubits can effectively simulate discrete time crystals with clear signatures that appear even in small arrays, where charge noise—typically detrimental to qubit performance—actually stabilizes the time-translation symmetry breaking phase. Second, we develop full configuration interaction methods to accurately model multi-electron quantum dots, revealing significant many-body effects that enhance tunneling couplings and improve device characterization beyond single-electron approximations. Finally, we introduce the Singlet-only Always-on Gapless Exchange (SAGE) qubit architecture, a four-electron encoding that eliminates sensitivity to local magnetic fields while maintaining all-electrical baseband control, and suppressing leakage. The SAGE qubit offers a promising pathway toward ultra-scalable quantum computation with spin qubits
Discovering the Hygroscopic Behavior of Atmospheric Aerosols with Vapor-Phase Transmission Electron Microscopy
No full textAtmospheric aerosols play a large role in cloud formation, radiative forcing, and precipitation. Inorganic and organic aerosol particles can act as seeds for cloud droplet formation through water adsorption and hygroscopic growth. In this work, we utilize in situ transmission electron microscopy to investigate the atomic structure and water uptake properties of atmospheric aerosols with nanometer scale spatial resolution and single second time resolution. This work reveals complex nanoscale water uptake dynamics that have not been previously observed and stresses the need to consider atomic and nanoscale structure and chemistry in water uptake models for atmospheric aerosols. We first used vapor-phase transmission electron microscopy (VPTEM) to directly image nanoscale condensation dynamics of sessile water droplets in electric fields. This work established the effect of the imaging electron beam on the water vapor–liquid equilibrium during VPTEM imaging. Simulations showed that the electron beam generated electric fields of ~108 V/m, which was high enough to depress the water vapor pressure and promote rapid nucleation of nanosized water droplets. A mass-balance model showed that droplet growth was consistent with electric-field-induced condensation, while droplet evaporation was consistent with a radiolysis-induced mechanism. This work identifies several electron beam–sample interactions that impact condensation dynamics and provides the fundamental understanding for the study of more complex vapor–liquid equilibria study with VPTEM in the future.Next, we used in situ VPTEM imaging of individual sodium chloride (NaCl) nanoparticles to visualize water adsorption and aerosol particle dissolution prior to and during deliquescence. This work demonstrates that deliquescence of simple pure salt particles with sizes in the range of 100 nm to several microns is not a spontaneous phase transition, and instead involves a range of complex dissolution and water-condensation dynamics.
Then, we imaged lab generated mixed sodium chloride (NaCl)–phthalic acid (PTA) aerosols with VPTEM. Comprehensive, high-resolution characterization demonstrated that the NaCl–PTA aerosols contained a single-crystal NaCl domain that was either fully or partially engulfed by an amorphous PTA shell. Humidity controlled in situ VPTEM revealed multistep water uptake dynamics that depended on the aerosol morphology. This work represents a first step in establishing a complete picture of how complex multicomponent aerosol particles take up water. Finally, we summarize the work in this dissertation and recommend future research avenues for VPTEM imaging of water uptake on atmospheric aerosols. The future work will focus on aged aerosol hygroscopic measurements and organic vapor condensation on aerosol particles, which extends the perspective of our study and the feasibility of VPTEM in aerosol research
BOWLS BETWEEN THE BAYS: EIGHTEENTH-CENTURY CERAMIC TRADE AND CONSUMPTION ON THE UPPER DELMARVA PENINSULA
No full textCeramics have been produced for thousands of years, and for much of that time innovators have attempted to invent new vessel forms and methods of decoration to create a unique product that would be appealing to the consumer. The seventeenth and eighteenth centuries comprised a period of booming consumerism, as evidenced by the number of locales of production dedicated to the innovation of new styles and decorative techniques applied to contemporaneous ceramic types. While the Navigation Acts limited colonial trade solely to Britain, colonists could import many types of ceramics from Britain, even those that were imported into Britain from the European mainland. Therefore, the colonists had an abundance of options to choose from when it came to vessel type and decoration. However, I and other archaeologists of the region have noticed a distinct separation between the ceramic types found in different parts of the greater Chesapeake region. As a result, I wished to see if a separation of types existed on the upper Delmarva Peninsula due to the trade routes used to ship these goods to each site of interest and, if distinct patterns exist, how these patterns are related to social and communal consumer preferences and ritualistic emulation of regional high-status individuals and families. 22 archaeological sites – 10 located on the Eastern Shore of Maryland and 12 located in Delaware – dating to the late-seventeenth and eighteenth centuries have been selected for study based on factors related to the material culture and the overall integrity of the site. Imported ceramic types from these sites will be examined to assess the region for patterns related to the trade and consumption of specific ceramic types over others. This thesis attempts to answer two distinct questions: how did patterns of trade and consumer behavior vary between the Chesapeake Bay region and Delaware River region during the eighteenth century? Also, how have these patterns associated with trade or differences in regional consumer behaviors and preferences resulted in the distribution of types across the Delmarva Peninsula and established associations of certain types with the ceramic assemblages from sites of one region over another? While similar studies into the comparison of ceramic types have been performed on individual sites and more closely related sites in the region, none have been so comprehensive to assess the entire upper Delmarva Peninsula in this way, and few have taken the approach of trade, consumer preference, and emulation in an attempt to explain the patterns in ceramic types in the region. While this thesis contributes to the study of the archaeological record of the Delmarva Peninsula, a peripheral region that is chronically overlooked and understudied during this period, it establishes a framework through which differences in the regional distribution of seventeenth- and eighteenth-century ceramic types based on consumerism and emulation can be explained
Erasure Correction for Graph Codes as a Problem of Bootstrap Percolation
No full textDistributed storage systems are designed to have the capability to recover the contents of failed nodes by accessing the contents of other functional nodes in the storage cluster. To achieve this property in storage systems, engineers have focused considerable effort on developing codes that enable local recovery. An encoding method is said to have locality if the contents of a storage node can be reconstructed by accessing other nodes in the storage cluster. An additional constraint faced by the designer is accounting for the underlying topology of the system that may affect the functioning of the recovery method. In this research, we study certain aspects of storage systems with graphical structure, modeling them as storage codes on graphs. A storage code is an assignment of bits to the vertices of a graph with the property that every vertex can recover its value from its neighbors.
Specializing the problem further, we assume that several vertices in the graph represent failed storage nodes, and the task of code construction is to support their recovery. Suppose that every vertex is erased with some probability independently from the other vertices,
and that the recovery proceeds in rounds, whereby the vertices with more than functional neighbors
are assumed to be able to recover themselves. As the number of erased vertices decreases, additional vertices
may be able to restore their values until all the erasures are corrected.
In graph-theoretic terms this procedure is known as {\em bootstrap percolation} with infection threshold (it is often called infection spread in graphs).
The research presented in this thesis extends earlier works on bootstrap percolation. We determine asymptotics of the critical probability of bootstrap percolation on the binary -dimensional hypercube, solving for several regimes of dependence of on the dimension . We also determine the maximum time to erasure recovery (the maximum percolation time) on the -ary hypercube graph. Extending the classical setting, we modify the hypercube graph to expand the neighborhood to allow vertices at distance or more, and compute the asymptotics of critical probability and obtain other similar asymptotic results