Institutional Repository

The UDSpace Institutional Repository collects and disseminates research material from the University of Delaware.

  • Faculty, staff, and graduate students can deposit their research material directly into UDSpace. Faculty may use UDSpace to fulfill the University of Delaware Faculty Senate Open Access Resolution, and in many cases may use it to fulfill open access requirements from grant funding agencies.
  • Departments can use UDSpace to publish or distribute their working papers, technical reports, or other research material.
  • UDSpace also includes all doctoral dissertations from winter 2014 forward, and all master's theses from fall 2009 forward.

To learn more about UDSpace, and how you can make your research openly accessible to the public, visit our UDSpace Policies website.


Recent Submissions

Weather drives variation in COVID-19 transmission and detection
(Environmental Research: Climate, 2023-01-26) Rising, James; Linsenmeier, Manuel; De Menezes, Ana
The debate over the influence of weather on COVID-19 epidemiological dynamics remains unsettled as multiple factors are conflated, including viral biology, transmission through social interaction, and the probability of disease detection. Here we distinguish the distinct dynamics of weather on detection and transmission with a multi-method approach combining econometric techniques with epidemiological models, including an extension of a susceptible-exposed-infectious-recovered model, to analyse data for over 4000 geographic units throughout the year 2020. We find distinct and significant effects of temperature, thermal comfort, solar radiation, and precipitation on the growth of infections. We also find that weather affects the rates of both disease transmission and detection. When we isolate transmission effects to understand the potential for seasonal shifts, the instantaneous effects of weather are small, with R0 about 0.007 higher in winter than in summer. However, the effects of weather compound over time, so that a region with a 5 ∘C drop over three months in winter is expected to have 190% more confirmed cases at the end of that 90 days period, relative to a scenario with constant temperature. We also find that the contribution of weather produces the largest effects in high-latitude countries. As the COVID-19 pandemic continues to evolve and risks becoming endemic, these seasonal dynamics may play a crucial role for health policy.
Transcriptomic Signature of the Simulated Microgravity Response in Caenorhabditis elegans and Comparison to Spaceflight Experiments
(Cells, 2023-01-10) Çelen, İrem; Jayasinghe, Aroshan; Doh, Jung H.; Sabanayagam, Chandran R.
Given the growing interest in human exploration of space, it is crucial to identify the effects of space conditions on biological processes. Here, we analyze the transcriptomic response of Caenorhabditis elegans to simulated microgravity and observe the maintained transcriptomic response after returning to ground conditions for four, eight, and twelve days. We show that 75% of the simulated microgravity-induced changes on gene expression persist after returning to ground conditions for four days while most of these changes are reverted after twelve days. Our results from integrative RNA-seq and mass spectrometry analyses suggest that simulated microgravity affects longevity-regulating insulin/IGF-1 and sphingolipid signaling pathways. Finally, we identified 118 genes that are commonly differentially expressed in simulated microgravity- and space-exposed worms. Overall, this work provides insight into the effect of microgravity on biological systems during and after exposure.
The use of airborne LiDAR data and semi-automated GIS tools for the identification and mapping of fluvial terraces along Powder River, Montana
(University of Delaware, 2022) Wiley, Katharine E.
This thesis compares river terrace polygons and elevation data from a semi-automated mapping program (TerEx) in ArcGIS to previously collected field-based polygons and elevation data over a 30 km stretch of Powder River’s valley in southeastern Montana. The purpose of this study is to determine if the polygon outputs of the semi-automated program matches with prior field, spatial (e.g. maps), and chronological (e.g. terrace elevations) interpretations. As determined by comparative geometric analyses and field observations, the semi-automated polygons rarely match with prior studies. Spatially, the TerEx program commonly creates too many polygons due to slight elevation differences and segmentations caused by agricultural activity, rough terrain, and roads. In other instances, the program output creates polygons that are too large predominantly in regions directly adjacent to alluvial fans where depositional and erosional processes are acting upon and altering the landscape. Large portions of the TerEx polygons fall within and aid in assessing previously identified chronological terrace elevation parameters. The sum of our data indicates that TerEx is useful in conjunction with extensive prior field-based data, but on its own would provide unreliable results.
Biostratigraphy and paleoecology of the Vincentown Manasquan, and Shark River Formations of northern Kent County, Delaware
(University of Delaware, 2022) Vincett, William K., III
The Vincentown, Manasquan, and Shark River Formations are three marine units deposited during the Paleocene and Eocene Epochs in the Atlantic Coastal Plain. This study analyzed the lithostratigraphy, planktonic foraminiferal biostratigraphy, and benthic foraminiferal biofacies from three cores in Kent County, Delaware. New planktonic foraminiferal biozonations from this study indicate that the Vincentown Formation in Delaware is late Paleocene (Zone P4c), the Manasquan Formation is early Eocene (Zones E1-E5), and the Shark River Formation is early to middle Eocene in age (Zones E7-E10). ☐ The Rancocas aquifer is found within the Vincentown Formation in Delaware, and is used for regional groundwater extraction. The Vincentown Formation changes from an aquifer sand to more muddy facies in a short distance near the Kent County-New Castle County boundary. Benthic foraminifera were compared to previous biofacies interpretations in New Jersey, and outer neritic biofacies are found throughout these three units, with some shallower middle neritic influence. The benthic foraminifera indicate that the Vincentown Formation in the updip coreholes is a coarse-grained outer neritic paleoenvironment with potentially some middle neritic influence, while the downdip Vincentown Formation is a finer-grained outer neritic paleoenvironment. Benthic foraminifera from the Manasquan Formation suggest middle neritic and outer neritic paleoenvironments. The Shark River Formation contains one sample with outer neritic benthic foraminifera, and other samples with more mixed results. These results indicate that there have been water depth changes with the Vincentown, Manasquan, and Shark River Formations through the Paleocene and Eocene in Delaware.
Does foraging success predict subsequent foraging behavior in Pygoscelis penguins?
(University of Delaware, 2022) Voirol, Grant
In a patchy prey environment, optimal foraging theory predicts that central place foragers will discretize horizontal movement and vertical movements into directed and resident foraging behaviors and that high foraging success should lead to similar sequential foraging trips. Here we use high resolution GPS and depth records to track the foraging locations and estimate forage success of two Pygoscelis penguin species in a known biological hotspot to test the predictions of optimal foraging theory. Over two breeding seasons, we tagged 71 penguins near Palmer Station in the West Antarctic Peninsula. We estimated foraging activity from the complexity of depth records and linked them to horizontal patterns of resident and directed movements measured by GPS tags. Contrary to theoretical expectations, we found that there was no relationship between movement modes and foraging rate. We also found that the degree of similarity between sequential trips was not predicted by foraging success, wind speed, or tidal stage. Sequential foraging trips were also not significantly more similar to each other than other non-sequential foraging trips. Our overall findings suggest that the penguins in this region forage during both directed and residential movements, which is not expected if they were following optimal foraging theory. The horizontal patterns of resident and directed movements were not good predictors of foraging activity. We suggest that the abundance and reliability of prey in the local region may explain why these penguin colonies do not follow the expectations of optimal foraging theory.