Physical Sciences and Mathematics Commons^™

Valley-Dependent Lorentz Force And Aharonov-Bohm Phase In Strained Graphene P-N Junction, Sanjay Prabhakar, Rabindra Nepal, Roderick Melnik, Alexey Kovalev

Department of Physics and Astronomy: Faculty Publications

Veselago lens focusing in graphene p−n junction is promising for realizations of new generation electron optics devices. However, the effect of the strain-induced Aharonov-Bohm interference in a p−n junction has not been discussed before. We provide an experimentally feasible setup based on the Veselago lens in which the presence of strain can result in both the valley-dependent Lorentz force and Aharonov-Bohm interference. In particular, by employing the Green's function and tight-binding methods, we study the strain induced by dislocations and line defects in a p−n junction and show how the resulting Aharonov-Bohm phase and interference can be detected. Furthermore, for …

Bridge Deck Delamination Segmentation Based On Aerial Thermography Through Regularized Grayscale Morphological Reconstruction And Gradient Statistics, Chongsheng Cheng, Zhexiong Shang, Zhigang Shen

Department of Construction Engineering and Management: Faculty Publications

Environmental and surface texture-induced temperature variation across the bridge deck is a major source of errors in delamination detection through thermography. This type of external noise poises a significant challenge for conventional quantitative methods such as global thresholding and k-means clustering. An iterative top-down approach is proposed for delamination segmentation based on grayscale morphological reconstruction. A weight-decay function was used to regularize the reconstruction for regional maxima extraction. The mean and coefficient of variation of temperature gradient estimated from delamination boundaries were used for discrimination. The proposed approach was tested on a lab experiment and an in-service bridge deck. The …

Convergence Science In The Anthropocene: Navigating The Known And Unknown, David G. Angeler, Craig R. Allen, Ana Carnaval

School of Natural Resources: Faculty Publications

1. Rapidly changing ecological and social systems currently pose significant societal challenges. Navigating the complexity of social-ecological change requires ap- proaches able to cope with, and potentially solve, both foreseen and unforeseen societal challenges.

2. The emergent field of convergence addresses the intricacies of such challenges, and is thus relevant to a broad range of interdisciplinary issues.

3. This paper suggests a way to conceptualize convergence research. It discusses how it relates to two major societal challenges (adaptation, transformation), and to the generation of policy-relevant science. It also points out limitations to the further development of convergence research.

Violation Of Centrosymmetry In Time-Resolved Coherent X-Ray Diffraction From Rovibrational States Of Diatomic Molecules, Hua-Chieh Shao, Anthony F. Starace

Anthony F. Starace Publications

Owing to increasing applications of time-resolved coherent x-ray scattering for the investigation of molecular reaction dynamics, we develop a theoretical model for time-dependent x-ray diffraction from molecular and/or electronic motion in molecules. Our model shows that the violation of centrosymmetry (VOC) is a general phenomenon in time-resolved diffraction patterns. We employ our theoretical model to illustrate the VOC in time-resolved coherent x-ray diffraction from two oriented diatomic molecules undergoing rovibrational motion: lithium hydride (LiD) and hydrogen (HD). Our simulations show asymmetric x-ray diffraction images that reflect the directions of the molecular motions.

Redescription Of Anaschisma (Temnospondyli: Metoposauridae) From The Late Triassic Of Wyoming And The Phylogeny Of The Metoposauridae, Bryan M. Gee, William G. Parker, Adam D. Marsh

United States National Park Service: Publications

Metoposaurids are non-marine temnospondyls that are among the most common constituents of Late Triassic deposits, but despite their abundance, the evolutionary relationships of the group are poorly resolved and have not been fully addressed with modern phylogenetic methods. The genus Anaschisma is one of a number of poorly resolved metoposaurid taxa and was erected to describe two species from the Popo Agie Formation (Carnian) in Wyoming: Anaschisma browni and Anaschisma brachygnatha. Since being named, the genus has been repeatedly synonymized and separated with other taxa in the context of broader revisions of the Metoposauridae. At present, Anaschisma is considered …

The Accelerating Influence Of Humans On Mammalian Macroecological Patterns Over The Late Quaternary, Felisa A. Smith, Rosemary E. Elliott Smith, S. Kathleen Lyons, Jonathan L. Payne, Amelia Villaseñor

School of Biological Sciences: Faculty Publications

The transition of hominins to a largely meat-based diet ~1.8 million years ago led to the exploitation of other mammals for food and resources. As hominins, particularly archaic and modern humans, became increasingly abundant and dispersed across the globe, a temporally and spatially transgressive extinction of large-bodied mammals followed; the degree of selectivity was unprecedented in the Cenozoic fossil record. Today, most remaining large-bodied mammal species are confined to Africa, where they coevolved with hominins. Here, using a comprehensive global dataset of mammal distribution, life history and ecology, we examine the consequences of “body size downgrading” of mammals over the …

Influence Of Strain And Chemical Substitution On The Magnetic Anisotropy Of Antiferromagnetic Cr2O3: An Ab-Initio Study, Sai Mu, Kirill D. Belashchenko

Department of Physics and Astronomy: Faculty Publications

The influence of the mechanical strain and chemical substitution on the magnetic anisotropy energy (MAE) of Cr₂O₃ is studied using first-principles calculations. Dzyaloshinskii-Moriya interaction contributes substantially to MAE by inducing spin canting when the antiferromagnetic order parameter is not aligned with the hexagonal axis. Nearly cubic crystal field results in a very small MAE in pure Cr₂O₃ at zero strain, which is incorrectly predicted to be negative (in-plane) on account of spin canting. The MAE is strongly modified by epitaxial strain, which tunes the crystal-field splitting of the t_2g triplet. The contribution from …

Improving Risk Assessment Of The Emergence Of Novel Influenza A Viruses By Incorporating Environmental Surveillance, Kim M. Pepin, Matthew W. Hopken, Susan A. Shriner, Erica Spackman, Zaid Abdo, Colin Parrish, Steven Steven, James O. Lloyd-Smith, Antoinette J. Piaggio

United States Department of Agriculture Wildlife Services: Staff Publications

Reassortment is an evolutionary mechanism by which influenza A viruses (IAV) generate genetic novelty. Reassortment is an important driver of host jumps and is widespread according to retrospective surveillance studies.However, predicting the epidemiological risk of reassortant emergence in novel hosts from surveillance data remains challenging. IAV strains persist and cooccur in the environment, promoting co-infection during environmental transmission. These conditions offer opportunity to understand reassortant emergence in reservoir and spillover hosts. Specifically, environmental RNA could provide rich information for understanding the evolutionary ecology of segmented viruses, and transform our ability to quantify epidemiological risk to spillover hosts. However, significant challenges …

Geophysical Analysis Of The Midcontinent Rift’S Subsurface Structure In Southeastern Nebraska, Patrick Szopinski

Honors Theses

The Midcontinent Rift System (MCRS) is a 1.1 billion-year-old failed rift system that spans much of the North American continental interior. The MCRS is exposed at Lake Superior and is buried in the subsurface along its southwest-extending arm through southeastern Nebraska. Due to the presence of buried volcanic rocks, the MCRS has characteristic highly-pronounced potential field anomalies (gravity and magnetic). Despite these large anomalies, not much is known about the subsurface faulting associated with the rift zone in the Midwest. The goal of this project is to attempt to use integrated analysis of collected geophysical data from multiple methods to …

Flood-Inundation Maps Of The Meramec River From Eureka To Arnold, Missouri, 2018, Benjamin J. Dietsch, Kellan R. Strauch

United States Geological Survey: Water Reports and Publications

Document abstract

Libraries of digital flood-inundation maps that spanned a combined 37.2-mile reach of the Meramec River that extended upstream from Eureka, Missouri, to downstream near the confluence of the Meramec and Mississippi Rivers were created by the U.S. Geological Survey (USGS) in cooperation with the United States Army Corps of Engineers, Metropolitan St. Louis Sewer District, Missouri Department of Transportation, Missouri American Water, Federal Emergency Management Agency Region 7, and the cities of Pacific, Eureka, Wildwood, and Arnold. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/, depict estimates of …

Studies Of Boundary Layer Transition From Laminar To Turbulent, Elizabeth Spaulding

Honors Theses

In engineering applications, there is a strong desire to reduce energy losses due to turbulent energy production. However, the theoretical understanding of turbulent and transition flow is still lacking due to the absence of an exact mathematical solution for turbulent flow. In the current project, transition and turbulent behavior in wall-bounded flow is studied, with an emphasis on concepts from boundary layer theory. Organized structures, such as streaks, waves, and vortices, which occur in such flows, are analyzed. Especially for near-wall structures, control strategies for suppressing such structures are discussed. Using mathematical equations which govern fluid flow, models for different …

Reflecting On Efforts To Design An Inclusive Citizen Science Project In West Baltimore, Amanda E. Sorensen, Rebecca C. Jordan, Shannon L. Ladeau, Dawn Biehler, Sacoby Wilson, John-Henry Pitas, Paul T. Leisnham

School of Natural Resources: Faculty Publications

Citizen science (CS) has been an increasingly utilized means by which scientists leverage members of the public to increase the amount of data collected and analyzed. However, the underrepresentation of individuals from certain socio-cultural groups can have consequences that can manifest in the scientific outcomes of those CS projects such as biases in the data. Additionally, this underrepresentation can potentially affect long-term viability and support of CS as a community of practice. CS programs that promote greater inclusivity would likely provide opportunities for communities to define, investigate, and address pressing issues in collaboration with professional scientists. In this paper we …

Earth Observation And Climate Services For Food Security And Agricultural Decision Making In South And Southeast Asia, Faisal M. Qamer, Tsegaue Tadesse, Mir Matin, Walter L. Ellenburg, Benjamin Zaitchik

Drought Mitigation Center: Faculty Publications

Deliberations on new developments in the use of Earth observation for agriculture and food security in South and Southeast Asia gathered 120 participants to discuss i) agricultural and hydrological drought monitoring and early warning systems, ii) crop mapping and yield estimation, and iii) risk financing and agrometeorological advisory services.

Using Artificial Neural Networks To Predict Future Dryland Responses To Human And Climate Disturbances, C.E. Buckland, R.M. Bailey, D.S.G. Thomas

Department of Earth and Atmospheric Sciences: Faculty Publications

Land degradation and sediment remobilisation in dryland environments is considered to be a significant global environmental problem. Given the potential for currently stabilised dune systems to reactivate under climate change and increased anthropogenic pressures, identifying the role of external disturbances in driving geomorphic response is vitally important. We developed a novel approach, using artificial neural networks (ANNs) applied to time series of historical reactivation-deposition events from the Nebraska Sandhills, to determine the relationship between historic periods of sand deposition in semi-arid grasslands and external climatic conditions, land use pressures and wildfire occurrence. We show that both vegetation growth and sediment …

Pascal's Triangle Modulo N And Its Applications To Efficient Computation Of Binomial Coefficients, Zachary Warneke

Honors Theses

In this thesis, Pascal's Triangle modulo n will be explored for n prime and n a prime power. Using the results from the case when n is prime, a novel proof of Lucas' Theorem is given. Additionally, using both the results from the exploration of Pascal's Triangle here, as well as previous results, an efficient algorithm for computation of binomial coefficients modulo n (a choose b mod n) is described, and its time complexity is analyzed and compared to naive methods. In particular, the efficient algorithm runs in O(n log(a)) time (as opposed to …

Thermographic Laplacian-Pyramid Filtering To Enhance Delamination Detection In Concrete Structure, Chongsheng Cheng, Ri Na, Zhigang Shen

Department of Construction Engineering and Management: Faculty Publications

Despite decades of efforts using thermography to detect delamination in concrete decks, challenges still exist in removing environmental noise from thermal images. The performance of conventional temperature-contrast approaches can be significantly limited by environment-induced non-uniform temperature distribution across imaging spaces. Time-series based methodologies were found robust to spatial temperature non-uniformity but requires extended period to collect data. A new empirical image filtering method is introduced in this paper to enhance the delamination detection using blob detection method that originated from computer vison. The proposed method employs a Laplacian of Gaussian filter to achieve multi-scale detection of abnormal thermal patterns by …

Multivariate Analysis Of Hydrochemical Data For Jewel Cave, Wind Cave, And Surrounding Areas, Andrew J. Long, James B. Paces, William G. Eldridge

United States National Park Service: Publications

Abstract

Jewel Cave National Monument and Wind Cave National Park in South Dakota contain two of the six longest caves worldwide. These caves contain subterranean lakes that are important points of intersection between the water table of the Madison aquifer and the caves. During 2015 to 2017, several subterranean lakes were discovered in Jewel Cave, which previously was thought to be above the regional water table. The objectives of this study were to better understand the hydrology of the recently discovered subterranean lakes in Jewel Cave and to evaluate their relation or possible connection to similar lakes in Wind Cave. …

Informative Group Testing For Multiplex Assays, Christopher R. Bilder, Joshua M. Tebbs, Christopher S. Mcmahan

Department of Statistics: Faculty Publications

Infectious disease testing frequently takes advantage of two tools–group testing and multiplex assays–to make testing timely and cost effective. Until the work of Tebbs et al. (2013) and Hou et al. (2017), there was no research available to understand how best to apply these tools simultaneously. This recent work focused on applications where each individual is considered to be identical in terms of the probability of disease. However, risk-factor information, such as past behavior and presence of symptoms, is very often available on each individual to allow one to estimate individual-specific probabilities. The purpose of our paper is to propose …

X-Ray Ptychography On Low-Dimensional Hard-Condensed Matter Materials, Xiaowen Shi, Nicolas Burdet, Bo Chen, Gang Xiong, Robert Streubel, Ross Harder, Ian K. Robinson

Robert Streubel Papers

Tailoring structural, chemical, and electronic (dis-)order in heterogeneous media is one of the transformative opportunities to enable new functionalities and sciences in energy and quantum materials. This endeavor requires elemental, chemical, and magnetic sensitivities at the nano/atomic scale in two- and three-dimensional space. Soft X-ray radiation and hard X-ray radiation provided by synchrotron facilities have emerged as standard characterization probes owing to their inherent element-specificity and high intensity. One of the most promising methods in view of sensitivity and spatial resolution is coherent diffraction imaging, namely, X-ray ptychography, which is envisioned to take on the dominance of electron imaging techniques …

Interim Performance Report, Lg‐71‐16‐0152‐16, Extending Intelligent Computational Image Analysis For Archival Discovery, March 2019, Elizabeth Lorang, Leen-Kiat Soh, John O'Brien

CDRH Grant Reports

The primary goal of "Extending Intelligent Computational Image Analysis for Archival Discovery" is to investigate the use of image analysis as a methodology for content identification, description, and information retrieval in digital libraries and other digitized collections. Building on work started under a National Endowment for the Humanities' Office of Digital Humanities Start-up Grant, our IMLS project seeks to 1) analyze and verify our previously developed image analysis approach and extend it so that it is newspaper agnostic, type agnostic, and language agnostic; 2) scale and revise the intelligent image analysis approach and determine the ideal balance between precision and …

Plant Community Composition And Structure Monitoring At Scotts Bluff National Monument, 2018 Data Report, Isabel W. Ashton

United States National Park Service: Publications

Abstract

This report presents the results of vegetation monitoring efforts in 2018 at Scotts Bluff National Monument (SCBL) by the Northern Great Plains Inventory and Monitoring Network (NGPN) and Fire Ecology Program (NGPFire). This was the eighth year of combined monitoring efforts.

Crew members from NGPN visited eight long-term monitoring plots to collect data on the plant communities at SCBL. This work is part of a long-term monitoring effort designed to provide a better understanding of the condition of the vegetation community and how it changes over time. NGPN staff measured species richness, herb-layer height, native and non-native species abundance, …

Operator Algebras Generated By Left Invertibles, Derek Desantis

Department of Mathematics: Dissertations, Theses, and Student Research

Operator algebras generated by partial isometries and their adjoints form the basis for some of the most well studied classes of C*-algebras. Representations of such algebras encode the dynamics of orthonormal sets in a Hilbert space.We instigate a research program on concrete operator algebras that model the dynamics of Hilbert space frames.

The primary object of this thesis is the norm-closed operator algebra generated by a left invertible $T$ together with its Moore-Penrose inverse $T^\dagger$. We denote this algebra by $\mathfrac{A}_T$. In the isometric case, $T^\dagger = T^*$ and $\mathfrac{A}_T$ is a representation of the Toeplitz algebra. Of particular interest …

Umphlett Qci March 2019, Natalie Umphlett

High Plains Regional Climate Center: Personnel Publications

Highlights for the Basin

Temperature Anomalies

Plains Snowpack

Agriculture

Energy

Transportation

Temperature

Precipitation

Search For Narrow Hγ Resonances In Proton-Proton Collisions At √S =13 Tev, A. M. Sirunyan

Department of Physics and Astronomy: Faculty Publications

A search for heavy, narrow resonances decaying to a Higgs boson and a photon (Hγ) has been performed in proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb⁻¹ collected with the CMS detector at the LHC in 2016. Events containing a photon and a Lorentz-boosted hadronically decaying Higgs boson reconstructed as a single, large-radius jet are considered, and the γ + jet invariant mass spectrum is analyzed for the presence of narrow resonances. To increase the sensitivity of the search, events are categorized depending on whether or not …

Nebraska Statewide Groundwater-Level Monitoring Report 2018, Aaron R. Young, Mark E. Burbach, Leslie M. Howard, Michele M. Waszgis, Sue Olafsen Lackey, Robert Matthew Joeckel

Conservation and Survey Division

The term “groundwater” has come to be all but synonymous with Nebraska. Nearly three-quarters of the total volume of the High Plains Aquifer lies beneath the State. Groundwater maintains our streams, our ecosystems, our people, and our vitally important agricultural economy. Nebraska’s total groundwater resource is vast, yet it is also vulnerable to natural and anthropogenic changes, necessitating a long-term commitment to wise management through informed decision making. Monitoring, studying, and reporting form the essential basis for such management and, ultimately, for meeting the myriad challenges presented by change.

The personnel of the Conservation and Survey Division (CSD) are pleased …

Ordered Growth Of Ferroelectric Diisopropylammonium-Bromide Microcrystals Through Slotted-Jar Growth And Lithographically Controlled Wetting, Andrew J. Fanning

Honors Theses

Organic molecular ferroelectrics show promise for industry applications because of their switchable high spontaneous polarization value, mechanical flexibility, and cost-effectiveness. Since these materials, namely diisopropylammonium bromide, exhibit ferroelectricity only in tandem with a high level of crystallinity, novel methods must be explored in order to ensure that high levels of crystallinity are achieved. This project seeked to perfect the methods of Slotted Jar Growth and Lithographically Controlled Wetting (LCW). Slotted Jar Growth uses temperature driven solution saturation to grow crystals on a desired substrate. LCW drives the growth of microscopic diisopropylammonium bromide crystals, in their ferroelectric phase, through the use …

Limits To The World’S Green Water Resources For Food, Feed, Fiber, Timber, And Bioenergy, Joep F. Schyns, Arjen Y. Hoekstra, Martijn J. Booij, Rick J. Hogeboom, Mesfin Mekonnen

Daugherty Water for Food Global Institute: Faculty Publications

Green water––rainfall over land that eventually flows back to the atmosphere as evapotranspiration––is the main source of water to produce food, feed, fiber, timber, and bioenergy. To understand how freshwater scarcity constrains production of these goods, we need to consider limits to the green water footprint (WFg), the green water flow allocated to human society. However, research traditionally focuses on scarcity of blue water––groundwater and surface water. Here we expand the debate on water scarcity by considering green water scarcity (WSg). At 5 × 5 arc-minute spatial resolution, we quantify WFg and the maximum sustainable level to this footprint (WFg,m), …

The Influence Of Fetch On The Holocene Thermal Structure Of Hidden Lake, Glacier National Park, Jeffery R. Stone, Jasmine E. Saros, Trisha L. Spanbauer

Department of Earth and Atmospheric Sciences: Faculty Publications

We use three-dimensional modeling of the basin of Hidden Lake, Montana, to assess the influence of effective fetch on diatom-inferred changes in mixing depths throughout the Holocene. The basin of Hidden Lake is characterized by a complex morphometry; for example, three-dimensional modeling of the lake basin indicates that a decrease in lake level of 2 m would result in complete isolation of the deepest part of the lake basin from the rest of the lake. Our model suggests that small changes in the lake surface elevation at Hidden Lake would produce threshold-like responses in effective fetch, which in turn would …

Newgeochemical Evidence For The Origin Of North America's Largest Dune Field, The Nebraska Sand Hills, Central Great Plains, Usa, Daniel R. Muhs, James R. Budahn

United States Geological Survey: Staff Publications

The Nebraska SandHills region is the largest dune field inNorthAmerica and has diverse aeolian landforms. It has been active during both the late Pleistocene and late Holocene. Despite decades of study, the source of sediment for this large sand sea is still controversial. Here we report new trace element compositions of aeolian sand that are compared to four hypothesized sediment sources, Tertiary rocks of the Arikaree Group and Ogallala Group, unconsolidated sands of Pliocene age, and Platte River systemsands. All four potential sources have amineralogy that is similar to the Nebraska Sand Hills. K/Rb, K/Ba, Sc-Th-La, Eu/Eu*, LaN/YbN, As/Sb, and …

Testing Pyroxenite Versus Peridotite Sources For Marine Basalts Using U-Series Isotopes, Lynne J. Elkins, Bernard Bourdon, Sarah Lambart

Department of Earth and Atmospheric Sciences: Faculty Publications

Geochemically enriched signatures in global oceanic basalts have long indicated a heterogeneous mantle source, but the role of lithologic heterogeneity in producing mantle partial melts, particularly fertile pyroxenite rocks, remains unclear. Uranium-series disequilibria in basalts are particularly sensitive to the increased garnet mode and melting rates of pyroxenite rocks, making the system a useful indicator of mantle lithologic heterogeneity in the melt region for oceanic basalts. Here we summarize evidence for the presence and importance of pyroxenite rocks in the upper mantle and their role in melt generation of mid-ocean ridge basalts and ocean island basalts, with a synthesis of …