Digital Commons Network^™

Optimization Of Nozzle, Application Height, And Speed For Uass Pesticide Applications, Trenton Houston

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Unmanned aerial spray systems (UASS) applications have the potential to be efficient pesticide application platforms under conditions that are not accessible or fit for typical pesticide application equipment. Although this type of application is still under development in the United States, UASS pesticide applications are common in Asia, as they have replaced backpack sprayers. There is limited literature on the optimization of UASS applications and many parameters need to be investigated to identify the best combination of application variables such as flight height, flight speed, and nozzle selection. The objectives were to identify the deposition patterns of a four rotor …

Access To Online Formative Assessments In Introductory Biology Courses: Investigating Barriers To Student Engagement, Allison M. Upchurch

School of Biological Sciences: Dissertations, Theses, and Student Research

Instructors use a variety of online formative assessment (FA) activities to support learning outside of class. Previous studies have revealed barriers for students in online courses, but little is known about the barriers students experience when completing online FA assignments. Understanding these barriers to access is critical to fostering more inclusive learning for all students. Using a framework from previous work in online learning, we examined student perceptions of online FA access with respect to five barrier categories: technical resources, instructor organization, social interactions, personal engagement, and learning environment. We developed and administered a survey to over 1200 undergraduate biology …

A General Equilibrium Assessment Of Covid-19’S Labor Productivity Impacts On China’S Regional Economies, Xi He, Edward J. Balistreri, Gyu Hyun Kim, Wendong Zhang

Department of Economics: Faculty Publications

This study introduces a database for analyzing COVID-19’s impacts on China’s regional economies. This database contains various sectoral and regional economic outcomes at the weekly and monthly level. In the context of a general equilibrium trade model, we first formulate a mathematical representation of the Chinese regional economy and calibrate the model with China’s multi-regional input-output table. We then utilize the monthly provincial and sectoral value-added and national trade series to estimate COVID-19’s province-by-month labor-productivity impacts from February 2020 to September 2020. As a year-on-year comparison, relative to February 2019 levels, we find an average 39.5% decrease in labor productivity …

Modeling And Analysis Of A 12kw Solar-Wind Hybrid Renewable Energy System, Ekaterina Muravleva

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

The increase in rate of depletion of natural resources in the last decade as well as the increased global focus on climate change has made the transition to renewable resources of energy a priority for various countries and organizations across the globe. The sporadic nature of energy generated by photovoltaic systems and wind energy conversion systems has led to an increased utilization of more reliable hybrid renewable energy systems. A combination of both solar and wind energy-based power generations systems reduces the impact of seasonal variation on the amount of power generated and therefore, can be used under varying weather …

One-Bit Algorithm Considerations For Sparse Pmcw Radar, Ethan Triplett

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Phase Modulated Continuous Wave (PMCW) radar an emerging technology for autonomous cars. It is more flexible than the current frequency modulated systems, offering better detection resolution, interference mitigation, and future development opportunities. The issue preventing PMCW adoption is the need for high sample-rate analog to digital converters (ADCs). Due to device limits, a large increase in cost and power consumption occurs for every added resolution bit for a given sampling rate. This thesis explores radar detection techniques for few-bit and 1-bit ADC measurements. 1-bit quantization typically results in poor amplitude estimation, which can limit detections if the target signals are …

Solar Radiation And Soil Moisture Drive Tropical Forest Understory Responses To Experimental And Natural Hurricanes, J. Aaron Hogan, Joanne M. Sharpe, Ashley Van Beusekom, Sarah Stankavich, Samuel Matta Carmona, John E. Bithorn, Jamarys Torres-Díaz, Grizelle González, Jess K. Zimmerman, Aaron B. Shiels

United States Department of Agriculture Wildlife Services: Staff Publications

Tropical forest understory regeneration occurs rapidly after disturbance with compositional trajectories that depend on species availability and environmental conditions. To predict future tropical forest regeneration dynamics, we need a deeper understanding of how pulse disturbance events, like hurricanes, interact with environmental variability to affect understory demography and composition. We examined fern and sapling mortality, recruitment, and community composition in relation to solar radiation and soil moisture using 17 years of forest dynamics data (2003–2019) from the Canopy Trimming Experiment in the Luquillo Experimental Forest, Puerto Rico. Solar radiation increased 150% and soil moisture increased 40% following canopy trimming of experimental …

Comparative Susceptibility Of Eastern Cottontails And New Zealand White Rabbits To Classical Rabbit Haemorrhagic Disease Virus (Rhdv) And Rhdv2, Fawzi Mohamed, Thomas Gidlewski, Mary L. Berninger, Heather M. Petrowski, Alexa J. Bracht, Carla Bravo De Rueda, Roger W. Barrette, Meredith Grady, Emily S. O'Hearn, Charles E. Lewis, Karen E. Moran, Tracy L. Sturgill, Lorenzo Capucci, J. Jeffrey Root

United States Department of Agriculture Wildlife Services: Staff Publications

Rabbit haemorrhagic disease virus (RHDV) is associated with high morbidity and mortality in the European rabbit (Oryctolagus cuniculus). In 2010, a genetically distinct RHDV named RHDV2 emerged in Europe and spread to many other regions, including North America in 2016. Prior to this study it was unknown if eastern cottontails (ECT(s); Sylvilagus floridanus), one of the most common wild lagomorphs in the United States, were susceptible to RHDV2. In this study, 10 wild-caught ECTs and 10 New Zealand white rabbits (NZWR(s); O. cuniculus) were each inoculated orally with either RHDV (RHDVa/GI.1a; n = 5 per species) or RHDV2 (a recombinant …

Genomic Prediction Accuracy Of Stripe Rust In Six Spring Wheat Populations By Modeling Genotype By Environment Interaction, Kassa Semagn, Muhammad Iqbal, Diego Jarquin, Harpinder Randhawa, Reem Aboukhaddour, Reka Howard, Izabela Ciechanowska, Momna Farzand, Raman Dhariwal, Colin W. Hiebert, Amidou N’Diaye, Curtis Pozniak, Dean Spaner

Department of Statistics: Faculty Publications

Some previous studies have assessed the predictive ability of genome-wide selection on stripe (yellow) rust resistance in wheat, but the effect of genotype by environment interaction (GEI) in prediction accuracies has not been well studied in diverse genetic backgrounds. Here, we compared the predictive ability of a model based on phenotypic data only (M1), the main effect of phenotype and molecular markers (M2), and a model that incorporated GEI (M3) using three cross-validations (CV1, CV2, and CV0) scenarios of interest to breeders in six spring wheat populations. Each population was evaluated at three to eight field nurseries and genotyped with …

Ultrafast Electron Diffraction: Visualizing Dynamic States Of Matter, D. Filipetto, P. Musumed, R. K. Li, B. J. Siwick, M. R. Otto, Martin Centurion, J. P.F. Nunes

Martin Centurion Publications

Since the discovery of electron-wave duality, electron scattering instrumentation has developed into a powerful array of techniques for revealing the atomic structure of matter. Beyond detecting local lattice variations in equilibrium structures with the highest possible spatial resolution, recent research efforts have been directed towards the long sought-after dream of visualizing the dynamic evolution of matter in real-time. The atomic behavior at ultrafast timescales carries critical information on phase transition and chemical reaction dynamics, the coupling of electronic and nuclear degrees of freedom in materials and molecules, the correlation between structure, function and previously hidden metastable or nonequilibrium states of …

Ultra-High Carrier Mobilities In Ferroelectric Domain Wall Corbino Cones At Room Temperature, Conor J. Mccluskey, Matthew G. Colbear, James P.V. Mcconville, Shane J. Mccartan, Jesi R. Maguire, Michele Conroy, Kalani Moore, Alan Harvey, Felix Trier, Ursel Bangert, Alexei Gruverman, Manuel Bibes, Amit Kumar, Raymong G.P. Mcquaid, J. Marty Gregg

Alexei Gruverman Publications

Recently, electrically conducting heterointerfaces between dissimilar band-insulators (such as lanthanum aluminate and strontium titanate) have attracted considerable research interest. Charge transport has been thoroughly explored and fundamental aspects of conduction firmly established. Perhaps surprisingly, similar insights into conceptually much simpler conducting homointerfaces, such as the domain walls that separate regions of different orientations of electrical polarisation within the same ferroelectric band-insulator, are not nearly so well-developed. Addressing this disparity, we herein report magnetoresistance in approximately conical 180° charged domain walls, which occur in partially switched ferroelectric thin film single crystal lithium niobate. This system is ideal for such measurements: firstly, …

Time-Varying Resonant Mass At Collider And Beam Dump Experiments, Jinhui Guo, Yuxuan He, Jia Liu, Xiao-Ping Wang, Ke-Pan Xie

Department of Physics and Astronomy: Faculty Publications

A new particle usually manifests itself as a single resonant peak located at its mass. We propose if the new particle mass is time-varying due to environmental effects, then its mass spectrum typically has a novel double-peak feature. A representative model is the kinetic mixing dark photon interacting with an ultralight complex scalar dark matter charged under U(1)'. We reanalyze the existing experiments, showing the constraints on such a model are drastically weakened than those on the traditional single-peak resonance model, due to the reduction of the luminosity exposure in each resonant mass bin. Consequently, for mass around tens …

First Search For Exclusive Diphoton Production At High Mass With Tagged Protons In Proton-Proton Collisions At √S =13 Tev, A. Tumasyan

Department of Physics and Astronomy: Faculty Publications

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp → pγγp with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb⁻¹ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeVat the LHC. Events are selected with a diphoton invariant mass above 350 GeVand with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons match the mass and rapidity …

Asymmetrical Spectral Continuum Between Anti-Stokes And Stokes Scattering Revealed In Low-Frequency Surface-Enhanced Raman Spectroscopy, Shuo Sun, Dhanusha T.N. Rathnayake, Yinsheng Guo

Department of Chemistry: Faculty Publications

An asymmetrical spectral continuum is observed in low-frequency surface-enhanced Raman spectroscopy (LF-SERS) in the terahertz (THz) region. This background continuum appears as a flat baseline in the Stokes side and a slope in the anti-Stokes side. Analysis shows this asymmetry originates from the different scaling of anti-Stokes and Stokes scattering with respect to the Bose−Einstein distribution. Such asymmetry is readily visible, under room temperature, in the low-frequency THz spectral range. Accounting for this spectral intensity asymmetry reveals the intrinsic continuum background of electronic origin, differing from local normal modes and collective relaxational motions. We also describe a numerical method, independent …

Vortex Sheet Sensitivity To Low-Level Vertical Shear And Airmass Temperature Perturbation, Adam L. Houston, George L. Limpert

Department of Earth and Atmospheric Sciences: Faculty Publications

A theoretical, numerical-modeling-based examination of the sensitivity of vortex sheets along airmass boundaries to the following three characteristics is presented: 1) boundary-normal component of the vertical wind shear, 2) boundary-parallel component of the vertical wind shear, and 3) temperature perturbation within the parent air mass of the boundary. The overall aim of this work is to advance understanding of the sensitivity of micro-α- tomeso-γ-scale vortex generation along airmass boundaries to the ambient environment. Density currents are simulated in a 2D domain that does not allow baroclinic generation of near-surface vertical vorticity (ζ_ns) with parameterized latent heating for convection …

The Ddt-Induced Decline Influenced Genetic Diversity In Naturally Recovered Peregrine Falcons (Falco Peregrinus) Nesting Within The Alaska Arctic And Eastern Interior, Sarah A. Sonsthagen,, Ted Swem, Skip Ambrose, Melanie J. Flamme, Clayton M. White, George K. Sage, Sandra L. Talbot

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We assessed the influence of the severe mid-20th century population decline on genetic diversity in nonaugmented Peregrine Falcon Falco peregrinus populations nesting within the Alaska Arctic and eastern Interior. Microsatellite and mitochondrial DNA (mtDNA) data were analysed for Peregrine Falcons sampled from three periods: pre-decline, decline and post-decline. The influence of the decline on genetic diversity differed between the two locales. The Alaska Arctic was characterized by shifts in mtDNA haplotype frequencies, increased inbreeding coefficient, reduction in effective population size and increase in private haplotypes, and a signature of post-decline population growth was detected; by contrast, the eastern Interior showed …

Induced Spin Textures At 3D Transition Metal–Topological Insulator Interfaces, Slimane Laref, Sumit Ghosh, Evgeny Y. Tsymbal, Aurelien Manchon

Department of Physics and Astronomy: Faculty Publications

While some of the most elegant applications of topological insulators, such as the quantum anomalous Hall effect, require the preservation of Dirac surface states in the presence of time-reversal symmetry breaking, other phenomena such as spin-charge conversion rather rely on the ability for these surface states to imprint their spin texture on adjacent magnetic layers. In this Rapid Communication, we investigate the spin-momentum locking of the surface states of a wide range of monolayer transition metals (3d-TM) deposited on top of Bi₂Se₃ topological insulators using first-principles calculations. We find an anticorrelation between the magnetic moment …

Mentoring Undergraduate Research In Mathematical Modeling, Glenn Ledder

Department of Mathematics: Faculty Publications

In writing about undergraduate research in mathematical modeling, I draw on my 31 years as a mathematics professor at the University of Nebraska–Lincoln, where I mentored students in honors’ theses, REU groups, and research done in a classroom setting, as well as my prior experience. I share my views on the differences between research at the undergraduate and professional levels, offer advice for undergraduate mentoring, provide suggestions for a variety of ways that students can disseminate their research, offer some thoughts on mathematical modeling and how to explain it to undergraduates, and discuss the challenges involved in broadening research participation …

Mentoring Undergraduate Research In Mathematical Modeling, Glenn Ledder

Department of Mathematics: Faculty Publications

In writing about undergraduate research in mathematical modeling, I draw on my 31 years as a mathematics professor at the University of Nebraska–Lincoln, where I mentored students in honors’ theses, REU groups, and research done in a classroom setting, as well as my prior experience. I share my views on the differences between research at the undergraduate and professional levels, offer advice for undergraduate mentoring, provide suggestions for a variety of ways that students can disseminate their research, offer some thoughts on mathematical modeling and how to explain it to undergraduates, and discuss the challenges involved in broadening research participation …

Superfluid Spin Transistor, Edward Schwartz, Bo Li, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

We propose to use the Hall response of topological defects, such as merons and antimerons, to spin currents in two-dimensional magnetic insulator with in-plane anisotropy for identification of the Berezinskii-Kosterlitz-Thouless (BKT) transition in a transistorlike geometry. Our numerical results relying on a combination of Monte Carlo and spin dynamics simulations show transition from spin superfluidity to conventional spin transport, accompanied by the universal jump of the spin stiffness and exponential growth of the transverse vorticity current. We propose a superfluid spin transistor in which the spin and vorticity currents are modulated by changes in density of free topological defects, e.g., …

The 30x30 Program: A Federal Land Grab?, J. David Aiken

Cornhusker Economics

In January 2021, the Biden Administration issued a climate policy executive order.[2] [or EO].[3] Section 216 of the Biden climate EO, Conserving & Protecting our Nation’s Lands & Waters, directed the U.S. Department of the Interior, the U.S. Department of Agriculture, and the U.S. Department of Commerce (which includes NOAA, the U.S. National Oceanic & Atmospheric Administration) to prepare a report “recommending steps that the United States should take, working with state, local, tribal and territorial governments, agricultural and forest landowners, fishermen and other key stakeholders to achieve the goal of conserving at least 30% of our lands and waters …

Population Genetics Reveals Bidirectional Fish Movement Across The Continental Divide Via An Interbasin Water Transfer, Audrey C. Harris, Sara J. Oyler-Mccance, Jennifer A. Fike, Matthew P. Fairchild, Christopher M. Kennedy, Harry J. Crockett, Dana L. Winkelman, Yoichiro Kanno

United States Geological Survey: Staff Publications

Interbasin water transfers are becoming an increasingly common tool to satisfy municipal and agricultural water demand, but their impacts on movement and gene flow of aquatic organisms are poorly understood. The Grand Ditch is an interbasin water transfer that diverts water from tributaries of the upper Colorado River on the west side of the Continental Divide to the upper Cache la Poudre River on the east side of the Continental Divide. We used single nucleotide polymorphisms to characterize population genetic structure in cutthroat trout (Oncorhynchus clarkii) and determine if fish utilize the Grand Ditch as a movement corridor. …

Characterizing The Interplay Of Rubisco And Nitrogenase Enzymes In Anaerobic-Photoheterotrophically Grown Rhodopseudomonas Palustris Cga009 Through A Genome-Scale Metabolic And Expression Model, Niaz Bahar Chowdhury, Adil Alsiyabi, Rajib Saha

Department of Chemical and Biomolecular Engineering: Faculty Publications

Rhodopseudomonas palustris CGA009 is a Gram-negative purple nonsulfur bacterium that grows phototrophically by fixing carbon dioxide and nitrogen or chemotrophically by fixing or catabolizing a wide array of substrates, including lignin breakdown products for its carbon and fixing nitrogen for its nitrogen requirements. It can grow aerobically or anaerobically and can use light, inorganic, and organic compounds for energy production. Due to its ability to convert different carbon sources into useful products during anaerobic growth, this study reconstructed a metabolic and expression (ME) model of R. palustris to investigate its anaerobic-photoheterotrophic growth. Unlike metabolic (M) models, ME models include transcription …

First-Order Phase Transition And Fate Of False Vacuum Remnants, Kiyoharu Kawana, Philip Lu, Ke-Pan Xie

Department of Physics and Astronomy: Faculty Publications

False vacuum remnants in first-order phase transitions in the early Universe can form compact objects which may constitute dark matter. Such remnants form because particles develop large mass gaps between the two phases and become trapped in the old phase. We focus on remnants generated in a class of models with trapped dark sector particles, trace their development, and determine their ultimate fate. Depending on model and phase transition parameters, the evolutionary endpoint of these remnants can be primordial black holes, Fermi-balls, Q-balls, or thermal balls, and they all have the potential to constitute some portion or the whole of …

Gull Plumages Are, And Are Not, What They Appear To Human Vision, Muir D. Eaton, Pilar Benites, Luke Campillo, Robert E. Wilson, Sarah A. Sonsthagen

School of Natural Resources: Faculty Publications

Clear correlations between human and bird visual assessments of color have been documented, and are often assumed, despite fundamental differences in human and avian visual physiology and morphology. Analyses of plumage colors with avian perceptual models have shown widespread hidden inter-sexual and inter-specific color variation among passerines perceived as monochromatic to humans, highlighting the uncertainty of human vision to predict potentially relevant variation in color. Herein, we use reflectance data from 13 Larus gull species as an exemplar data set to study concordance between human vision and avian visual modeling of feather colors near, or below, the human threshold for …

The Natural History And Ecology Of Melanism In Red Wolf And Coyote Populations Of The Southeastern United States – Evidence For Gloger’S Rule, Joseph W. Hinton, Kyla M. West, Daniel J. Sullivan, Jacqueline L. Frair, Michael J. Chamberlain

United States Environmental Protection Agency: Publications

Background: Gloger’s rule postulates that animals should be darker colored in warm and humid regions where dense vegetation and dark environments are common. Although rare in Canis populations, melanism in wolves is more common in North America than other regions globally and is believed to follow Gloger’s rule. In the temperate forests of the southeastern United States, historical records of red wolf (Canis rufus) and coyote (Canis latrans) populations document a consistent presence of melanism. Today, the melanistic phenotype is extinct in red wolves while occurring in coyotes and red wolf-coyote hybrids who occupy the …

Foraging Habitat Selection Of Shrubland Bird Community In Tropical Dry Forest, Anant Deshwal, Steven L. Stephenson, Pooja Panwar, Brett A. Degregorio, Ragupathy Kannan, John D. Willson

United States Geological Survey: Staff Publications

Habitat loss due to increasing anthropogenic disturbance is the major driver for bird population declines across the globe. Within the Eastern Ghats of India, shrubland bird communities are threatened by shrinking of suitable habitats due to increased anthropogenic disturbance and climate change. The development of an effective habitat management strategy is hampered by the absence of data for this bird community. To address this knowledge gap, we examined foraging sites for 14 shrubland bird species, including three declining species, in three study areas representing the shrubland type of forest community in the Eastern Ghats. We recorded microhabitat features within an …

Exploring The Metabolic Landscape Of Pancreatic Ductal Adenocarcinoma Cells Using Genome-Scale Metabolic Modeling, Mohammad Mazharul Islam, Andrea Goertzen, Pankaj K. Singh, Rajib Saha

Department of Chemical and Biomolecular Engineering: Faculty Publications

Pancreatic ductal adenocarcinoma (PDAC) is a major research focus because of its poor therapy response and dismal prognosis. PDAC cells adapt their metabolism to the surrounding environment, often relying on diverse nutrient sources. Because traditional experimental techniques appear exhaustive to find a viable therapeutic strategy, a highly curated and omics-informed PDAC genome-scale metabolic model was reconstructed using patient-specific transcriptomics data. From the model-predictions, several new metabolic functions were explored as potential therapeutic targets in addition to the known metabolic hallmarks of PDAC. Significant downregulation in the peroxisomal beta oxidation pathway, flux modulation in the carnitine shuttle system, and upregulation in …

The Status Of Posidonia Oceanica At Tremiti Islands Marine Protected Area (Adriatic Sea), Andrea Tursi, Francesco Mastrototaro, Federica Montesanto, Francesco De Giosa, Anna Lisco, Antonella Bottalico, Giovanni Chimienti

School of Natural Resources: Faculty Publications

Simple Summary: The seagrass Posidonia oceanica is the most important marine phanerogam of the Mediterranean Sea due to its meadows’ complexity, persistence, and extension. These habitats provide a suite of ecosystem goods and services, being of primary importance in marine conservation. Despite their central role in the coastal ecology, P. oceanica meadows are undergoing overall deterioration and fragmentation in the basin mostly due to anthropogenic impacts at local to global scales. In the last decades, several management measures have been proposed aiming to improve the meadow health conditions, while the periodic monitoring of P. oceanica meadows allows for verifying their …

When Sarah Meets Lawrence: The Effects Of Coeducation On Women's College Major Choices, Avery Calkins, Ariel J. Binder, Dana Shaat, Brenden Timpe

Department of Economics: Faculty Publications

We leverage variation in the adoption of coeducation by U.S. women's colleges to study how exposure to a mixed-gender collegiate environment affects women's human capital investments. Our event-study analyses of newly collected historical data find a 3.0-3.5 percentage-point (30-33%) decline in the share of women majoring in STEM. While coeducation caused a large influx of male peers and modest increase in male faculty, we find no evidence that it altered the composition of the female student body or other gender-neutral inputs. Extrapolation of our main estimate suggests that coeducational environments explain 36% of the current gender gap in STEM.

On Approximating Total Variation Distance, Arnab Bhattacharyya, Sutanu Gayen, Kuldeep S. Meel, Dimitrios Myrisiotis, A. Pavan, N. V. Vinodchandran

School of Computing: Faculty Publications

Total variation distance (TV distance) is a fundamental notion of distance between probability distributions. In this work, we introduce and study the computational problem of determining the TV distance between two product distributions over the domain {0, 1}ⁿ. We establish the following results.

1. Exact computation of TV distance between two product distributions is #P-complete. This is in stark contrast with other distance measures such as KL, Chi-square, and Hellinger which tensorize over the marginals.

2. Given two product distributions P and Q with marginals of P being at least 1/2 and marginals of Q being at most …