Physical Sciences and Mathematics Commons^™

Interface Engineered Electron And Hole Tunneling, R. Guo, L. Tao, M. Li, Z. Liu, W. Lin, G. Zhou, X. Chen, X. Yan, H. Tian, E. Y. Tsymbal, And J. Chen

Evgeny Tsymbal Publications

No abstract provided.

Van Der Waals Multiferroic Tunnel Junctions, Y. Su, X. Li, M. Zhu, J. Zhang, L. You, And E. Y. Tsymbal

Evgeny Tsymbal Publications

No abstract provided.

Resonant Band Engineering Of Ferroelectric Tunnel Junctions, J. Su, X. Zheng, Z. Wen, T. Li, S. Xie, K. M. Rabe, X. Liu, And E. Y. Tsymbal

Evgeny Tsymbal Publications

No abstract provided.

Two-Dimensional Antiferroelectric Tunnel Junction, J. Ding, D.-F. Shao, M. Li, L.-W. Wen, And E. Y. Tsymbal

Evgeny Tsymbal Publications

No abstract provided.

Spin Superfluidity In Noncollinear Antiferromagnets, Bo Li, Alexey Kovalev

Alexey Kovalev Papers

We explore the spin superfluid transport in exchange interaction-dominated three-sublattice antiferromagnets. The system in the long-wavelength regime is described by an SO(3) invariant field theory. Additional corrections from Dzyaloshinskii-Moriya interactions or anisotropies can break the symmetry; however, the system still approximately holds a U(1)-rotation symmetry. Thus, the power-law spatial decay signature of spin superfluidity is identified in a nonlocal-measurement setup where the spin injection is described by the generalized spin-mixing conductance. We suggest iron jarosites as promising material candidates for realizing our proposal.

Spirals And Skyrmions In Antiferromagnetic Triangular Lattices, Wuzhang Fang, Aldo Raeliarijaona, Po-Hao Chang, Alexey Kovalev, K. D. Belashchenko

Alexey Kovalev Papers

We study realizations of spirals and skyrmions in two-dimensional antiferromagnets with a triangular lattice on an inversion-symmetry-breaking substrate. As a possible material realization, we investigate the adsorption of transition-metal atoms (Cr, Mn, Fe, or Co) on a monolayer of MoS2, WS2, or WSe2 and obtain the exchange, anisotropy, and Dzyaloshinskii-Moriya interaction parameters using first-principles calculations. Using energy minimization and parallel-tempering Monte Carlo simulations, we determine the magnetic phase diagrams for a wide range of interaction parameters. We find that skyrmion lattices can appear even with weak Dzyaloshinskii-Moriya interactions, but their stability is hindered by magnetic anisotropy. However, a weak easy …

Surface Acoustic Waves Increase Magnetic Domain Wall Velocity, Anil Adhikari, Shireen Adenwalla

Shireen Adenwalla Papers

Domain walls in magnetic thin films are being explored for memory applications and the speed at which they move has acquired increasing importance. Magnetic fields and currents have been shown to drive domain walls with speeds exceeding 500 m/s. We investigate another approach to increase domain wall velocities, using high frequency surface acoustic waves to create standing strain waves in a 3 micron wide strip of magnetic film with perpendicular anisotropy. Our measurements, at a resonant frequency of 248.8 MHz, indicate that domain wall velocities increase substantially, even at relatively low applied voltages. Our findings suggest that the strain wave …

Rwanda To Phase Out Polluting Vehicles By 2040, An Efficient Strategy To Mitigate Global Warming Effects?, Josue Kwizera

Op-Eds from ENSC230 Energy and the Environment: Economics and Policies

Passenger vehicles are major pollutants because on average a typical passenger vehicle emits about 4.6 metric tons of carbon dioxide per year. I highly support the idea that Rwanda joined on November 11, 2021, a group of countries at the COP26 UN climate talks that have made an agreement to end polluting vehicles by 2040. Rwanda is a landlocked country with a 12.95 million population as of 2020(world bank). Rwanda currently has over 221,000 registered vehicles; 83980 are passenger vehicles, 114,900 vehicles (52 percent of those vehicles) are motorcycles and the rest include public transports (buses and minibuses) and trucks …

30 By 30, Laron Core

Op-Eds from ENSC230 Energy and the Environment: Economics and Policies

Biden’s 30 by 30 plan, a regulatory approach to conservation, an imminent response to environmental action, a promise of inclusivity to all stakeholders. Or a broken promise in the making, an environmental policy inadequate to deliver sufficient results to its stakeholders? I am set to believe Biden’s 30 by 30 plan could very well be DOA.

Dynamic Manipulation Of Droplets Using Mechanically Tunable Microtextured Chemical Gradients, Ali J. Mazaltarim, John J. Bowen, Jay M. Taylor, Stephen Morin

Chemistry Department: Faculty Publications

Materials and strategies applicable to the dynamic transport of microdroplets are relevant to surface fluidics, self-cleaning materials, thermal management systems, and analytical devices. Techniques based on electrowetting, topographic micropatterns, and thermal/chemical gradients have advanced considerably, but dynamic microdroplet transport remains a challenge. This manuscript reports the fabrication of mechano-tunable, microtextured chemical gradients on elastomer films and their use in controlled microdroplet transport. Specifically, discreet mechanical deformations of these films enabled dynamic tuning of the microtextures and thus transport along surface-chemical gradients. The interplay between the driving force of the chemical gradient and the microtopography was characterized, facilitating accurate prediction of …

Terrestrial Ecological Risk Analysis Via Dietary Exposure At Uranium Mine Sites In The Grand Canyon Watershed (Arizona, Usa), Jo Ellen Hinck, Danielle Cleveland, Bradley E. Sample

United States Geological Survey: Staff Publications

The U.S. Department of the Interior recently included uranium (U) on a list of mineral commodities that are considered critical to economic and national security. The uses of U for commercial and residential energy production, defense applications, medical device technologies, and energy generation for space vehicles and satellites are known, but the environmental impacts of uranium extraction are not always well quantified. We conducted a screening-level ecological risk analysis based on exposure to miningrelated elements via diets and incidental soil ingestion for terrestrial biota to provide context to chemical characterization and exposures at breccia pipe U mines in northern Arizona. …

Managing For Radical Ecosystem Change: Applying The Resist-Accept- Direct (Rad) Framework, Abigail J. Lynch, Laura M. Thompson, Erik A. Beever, David N. Cole, Augustin C. Engman, Cat Hawkins Hoffman, Stephen T. Jackson, Trevor J. Krabbenhoft, David J. Lawrence, Douglas Limpinsel, Robert T. Magill, Tracy A. Melvin, John M. Morton, Robert A. Newman, Jay O. Peterson, Mark T. Porath, Frank J. Rahel, Gregor W. Schuurman, Suresh A. Sethi, Jennifer L. Wilkening

United States Geological Survey: Staff Publications

Ecosystem transformation involves the emergence of persistent ecological or social–ecological systems that diverge, dramatically and irreversibly, from prior ecosystem structure and function. Such transformations are occurring at increasing rates across the planet in response to changes in climate, land use, and other factors. Consequently, a dynamic view of ecosystem processes that accommodates rapid, irreversible change will be critical for effectively conserving fish, wildlife, and other natural resources, and maintaining ecosystem services. However, managing ecosystems toward states with novel structure and function is an inherently unpredictable and difficult task. Managers navigating ecosystem transformation can benefit from considering broader objectives, beyond a …

Ecology Of An Isolated Muskrat Population During Regional Population Declines, Laken S. Ganoe, Matthew J. Lovallo, Justin D. Brown, W. David Walter

United States Geological Survey: Staff Publications

Evidence indicating a decline in Ondatra zibethicus (Muskrat) populations in the United States during the past 40 years has led to speculation regarding factors influencing Muskrat survival. In order to understand population dynamics and survival, it is important to first define the ecology of local populations. We investigated the dwelling structure use, movements, home range, and survival of radio-tagged Muskrats (n = 14) in an urban wetland complex in central Pennsylvania. We used locations collected from intensive radio-telemetry monitoring to determine number of lodging structures used, hourly movement, and size and percent area overlap of home ranges. Muskrats shared …

Temporal Invariance Of Social-Ecological Catchments, Mark A. Kaemingk, Christine N. Bender, Chris Chizinski, Aaron J. Bunch, Kevin L. Pope

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Natural resources such as waterbodies, public parks, and wildlife refuges attract people from varying distances on the landscape, creating “social-ecological catchments.” Catchments have provided great utility for understanding physical and social relationships within specific disciplines. Yet, catchments are rarely used across disciplines, such as its application to understand complex spatiotemporal dynamics between mobile human users and patchily distributed natural resources. We collected residence ZIP codes from 19,983 angler parties during 2014–2017 to construct seven angler–waterbody catchments in Nebraska, USA. We predicted that sizes of dense (10% utilization distribution) and dispersed (95% utilization distribution) angler–waterbody catchments would change across seasons and …

Roost Use And Movements Of Northern Long-Eared Bats In A Southeast Nebraska Agricultural Landscape, Christopher Fill, Craig R. Allen, John F. Benson, Dirac Twidwell

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Bats are important bio-indicators of ecosystem health and provide a number of ecosystem services. White-nose Syndrome and habitat loss have led to the decline of many bat species in eastern North America, including the federally threatened northern long-eared bat, Myotis septentrionalis. White-nose Syndrome was only recently found in Nebraska, which lies on the western extent of this species geographic range. To better understand how this forest-dependent species persists in an agriculturally dominated landscape amid a growing number of pressures, we investigated the roosting habits of this bat at the Homestead National Monument of America, located in southeast Nebraska. We …

Impacts Of Extreme Environmental Disturbances On Piping Plover Survival Are Partially Moderated By Migratory Connectivity, Kristen S. Ellis, Michael J. Anteau, Francesca J. Cuthbert, Cheri L. Gratto-Trevor, Joel G. Jorgensen, David J. Newstead, Larkin Powell, Megan M. Ring, Mark H. Sherfy, Rose J. Swift, Dustin L. Toy, David N. Koons

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Effective conservation for listed migratory species requires an understanding of how drivers of population decline vary spatially and temporally, as well as knowledge of range-wide connectivity between breeding and nonbreeding areas. Environmental conditions distant from breeding areas can have lasting effects on the demography of migratory species, yet these consequences are often the least understood. Our objectives were to 1) evaluate associations between survival and extreme environmental disturbances at nonbreeding areas, including hurricanes, harmful algal blooms, and oil spills, and 2) estimate migratory connectivity between breeding and nonbreeding areas of midcontinental piping plovers (Charadrius melodus). We used capture …

Game-Theoretic Analysis Of Effort Allocation Of Contributors To Public Projects, Jared Soundy, Chenhao Wang, Clay Stevens, Hau Chan

CSE Conference and Workshop Papers

Public projects can succeed or fail for many reasons such as the feasibility of the original goal and coordination among contributors. One major reason for failure is that insufficient work leaves the project partially completed. For certain types of projects anything short of full completion is a failure (e.g., feature request on software projects in GitHub). Therefore, project success relies heavily on individuals allocating sufficient effort. When there are multiple public projects, each contributor needs to make decisions to best allocate his/her limited effort (e.g., time) to projects while considering the effort allocation decisions of other strategic contributors and his/her …

A Review Of Spatial Causal Inference Methods For Environmental And Epidemiological Applications, Brian J. Reich, Shu Yang, Yawen Guan, Andrew B. Giffin, Matthew J. Miller, Ana Rappold

Department of Statistics: Faculty Publications

The scientific rigor and computational methods of causal inference have had great impacts on many disciplines but have only recently begun to take hold in spatial applications. Spatial causal inference poses analytic challenges due to complex correlation structures and interference between the treatment at one location and the outcomes at others. In this paper, we review the current literature on spatial causal inference and identify areas of future work. We first discuss methods that exploit spatial structure to account for unmeasured confounding variables. We then discuss causal analysis in the presence of spatial interference including several common assumptions used to …

Treatment Of Inconclusive Results In Firearms Error Rate Studies, Heike Hofmann, Susan Vanderplas, Alicia L. Carriquiry

Department of Statistics: Faculty Publications

★ Defining error rates for firearms evidence ★ Impact of inconclusive decisions on error rates ★ Predictive probabilities and errors

Age And Paleoenvironmental Significance Of The Frazer Beach Member—A New Lithostratigraphic Unit Overlying The End-Permian Extinction Horizon In The Sydney Basin, Australia, Stephen Mcloughlin, Robert S. Nicoll, James L. Crowley, Vivi Vajda, Chris Mays, Christopher R. Fielding, Tracy D. Frank, Alexander Wheeler, Malcolm Bocking

Department of Earth and Atmospheric Sciences: Faculty Publications

The newly defined Frazer Beach Member of the Moon Island Beach Formation is identified widely across the Sydney Basin in both outcrop and exploration wells. This thin unit was deposited immediately after extinction of the Glossopteris flora (defining the terrestrial end- Permian extinction event). The unit rests conformably on the uppermost Permian coal seam in most places. A distinctive granule-microbreccia bed is locally represented at the base of the member. The unit otherwise consists of dark gray to black siltstone, shale, mudstone and, locally, thin lenses of fine-grained sandstone and tuff. The member represents the topmost unit of the Newcastle …

Opening Of The Gulf Of Mexico: What We Know, What Questions Remain, And How We Might Answer Them, Irina Filina, James Austin, Tony Doré, Elizabeth Johnson, Daniel Minguez, Ian Norton, John Snedden, Robert J. Stern

Department of Earth and Atmospheric Sciences: Faculty Publications

The Gulf of Mexico is an economically important basin with more than a century-long history of hydrocarbon exploration. However, the opening history of the basin remains debated for two reasons: 1) the quality of data does not allow for reliable interpretations of crustal features beneath thick and complex overburden, and 2) most industry well and geophysical data are proprietary. The last concerted effort by industry and academia to summarize the state of knowledge regarding the Gulf of Mexico’s formation was three decades ago and resulted in publication of a major volume as part of the Decade of North American Geology …

The Rise And Fall Of Wiñaymarka: Rethinking Cultural And Environmental Interactions In The Southern Basin Of Lake Titicaca, Maria C. Bruno, José M. Capriles, Christine A. Hastorf, Sherilyn C. Fritz, D. Marie Weide, Alejandra I. Domic, Paul A. Baker

Department of Earth and Atmospheric Sciences: Faculty Publications

Investigations of how past human societies managed during times of major climate change can inform our understanding of potential human responses to ongoing environmental change. In this study, we evaluate the impact of environmental variation on human communities over the last four millennia in the southern Lake Titicaca basin of the Andes, known as Lake Wiñaymarka. Refined paleoenvironmental reconstructions from new diatom-based reconstructions of lake level together with archaeological evidence of animal and plant resource use from sites on the Taraco Peninsula, Bolivia, reveal frequent climate and lake-level changes within major cultural phases. We posit that climate fluctuations alone do …

Biden’S “Blue” Hydrogen Plan Is Not The Answer, Ryan Martz

Op-Eds from ENSC230 Energy and the Environment: Economics and Policies

The excitement about hydrogen as a fuel and energy source is similar to buying an electric vehicle (EV) thinking it will reduce your personal CO₂ emissions. On the surface, it seems great! No greenhouse gas emissions while driving is certainly better than the greenhouse gasses released from a normal combustion engine car, but when you consider other effects, it’s no longer as great. What if the grid that you plug your EV into is powered primarily by coal? What about the environmental and human rights impacts of mining the materials to make the batteries? What about the lack of …

Annual Report 2020 Conservation And Survey Division, Robert Matthew Joeckel

Conservation and Survey Division

The Conservation and Survey Division (Nebraska Geological Survey), the natural resource survey component of the School of Natural Resources, is a unique, multi-disciplinary research, service and data-collection organization established by state statute in 1921.

The Division's mission is to investigate and record information about Nebraska's geologic history, its rock and mineral resources, the quantity and quality of its water resources, land cover and other aspects of its geography, as well as the nature, distribution and uses of its soils.

Magnetism In Curved Geometries, Robert Streubel, Evgeny Y. Tsymbal, Peter Fischer

Robert Streubel Papers

Curvature impacts physical properties across multiple length scales, ranging from the macroscopic scale, where the shape and size vary drastically with the curvature, to the nanoscale at interfaces and inhomogeneities in materials with structural, chemical, electronic, and magnetic short-range order. In quantum materials, where correlations, entanglement, and topology dominate, the curvature opens the path to novel characteristics and phenomena that have recently emerged and could have a dramatic impact on future fundamental and applied studies of materials. Particularly, magnetic systems hosting non-collinear and topological states and 3D magnetic nanostructures strongly benefit from treating curvature as a new design parameter to …

Distribution Of Green Spaces In Omaha, Nebraska, Sofia Gavia

Department of Environmental Studies: Undergraduate Student Theses

The distribution of parks often depends on the races, ethnicity, and socioeconomic class of a community’s households. Parks and green spaces provides community residents recreational opportunities, economic benefits, and improves community public health. The unequal distribution of parks and green spaces in a city is a social issue found across the country. Limited research has been done on the relationship between green spaces and park access and social justice in Omaha, Nebraska. This study discusses whether there is a difference in how parks are distributed in Omaha, NE in terms of social justice and equitable distribution. Research is done using …

Diversification Of Angiosperms During The Cretaceous Period, Sakia Fields

Department of Environmental Studies: Undergraduate Student Theses

The topic of the Angiosperms relatively sudden appearance and diversification is a topic that has puzzled plenty of biologists and is even referred to as an “abominable mystery” by Charles Darwin. Up to date, many hypotheses have been proposed using various forms of data to form them. The available knowledge used to evaluate this topic has changed over the years, which has created some theme shifts. Some of the best supported of these hypotheses are more recent, but this does not make older articles unworthy of being evaluated, as they still often have relevant information. In the past, their appearance …

Analysis Of Drinking Water Disinfection Options, Bryce Carlen

Department of Environmental Studies: Undergraduate Student Theses

This thesis utilizes existing research to provide a framework that can be used for community and disaster planning. It analyses the critical process of water disinfection for drinking water. It focuses on chemical, distillation, and ultraviolet treatments in both centralized and point-of-use treatment. This thesis aims to provide a method for communities to determine the optimal water treatment, utilizing a framework based on weighted criteria. The decision-making framework is an easy-to-use and flexible process that communities can tailor for their specific needs to find the optimal treatment relative to their needs. In this study’s generalized example, ultraviolet treatment and distillation …

Audit Of Waste Collected Over One Week From Superior Dental Health Of Lincoln, Bryclin Alstrom

Department of Environmental Studies: Undergraduate Student Theses

A waste audit of Superior Dental Health of Lincoln was conducted in order to propagate the implementation of sustainable waste management practices within the company. Differentiating between hazardous waste and solid waste is necessary for environmentally friendly waste management and ceasing the spread of infectious pathogens. The audit identified nine different materials contributing to the biomedical waste stream of the company. Of which, personal protective equipment (PPE) is of major concern due to the financial commitment necessary to acquire / dispose of these products, as well as the strain in supply due to the current COVID-19 pandemic. The results of …

Long-Term Impacts Of 2019 Flood Experiences On Nebraskans’ Climate Change Perceptions, Caitlin Kingsley

Department of Environmental Studies: Undergraduate Student Theses

This study examines climate change perceptions in Nebraskans who experienced or witnessed flooding in March 2019. The purpose is to determine the impacts of 2019 flood experiences on Nebraskans’ climate change perceptions. The objectives are to determine the influence of flood proximity on changes in climate change perceptions, determine whether 2019 flooding had long-term impacts on Nebraskans’ climate change perceptions, and determine the influence of personal background factors on perceptions. A three-phase interview was utilized to collect background information, climate change perceptions, 2019 flood experiences, and relationships between 2019 flood experiences and climate change perceptions. Background information and climate change …