Physical Sciences and Mathematics Commons^™

Boundary Conditions And Berry Phase In Magnetic Nanostructures, A. Ullah, B. Balamurugan, W. Zhang, D. J. Sellmyer, R. Skomski

Nebraska Center for Materials and Nanoscience: Faculty Publications

The effect of micromagnetic boundary conditions on the Berry curvature and topological Hall effect in granular nanostructures is investi- gated by model calculations. Both free surfaces and grain boundaries between interacting particles or grains affect the spin structure. The Dzyaloshinskii-Moriya interactions yield corrections to the Erdmann-Weierstrass boundary conditions, but the Berry curvature remains an exclusive functional of the local spin structure, which greatly simplifies the treatment of nanostructures. An explicit example is a model nanostructure with cylindrical symmetry whose spin structure is described by Bessel function and which yields a mean-field-type Hall-effect contribution that can be related to magnetic-force-microscopy images.

Radiation Tolerance In Nano-Structured Crystalline Fe(Cr)/Amorphous Sioc Composite, Qing Su, Tianyao Wang, Lin Shao, Michael Nastasi

Nebraska Center for Materials and Nanoscience: Faculty Publications

The management of irradiation defects is one of key challenges for structural materials in current and future reactor systems. To develop radiation tolerant alloys for service in extreme irradiation environments, the Fe self-ion radiation response of nanocomposites composed of amorphous silicon oxycarbide (SiOC) and crystalline Fe(Cr) were examined at 10, 20, and 50 displacements per atom damage levels. Grain growth in width direction was observed to increase with increasing irradiation dose in both Fe(Cr) films and Fe(Cr) layers in the nanocomposite after irradiation at room temperature. However, compared to the Fe(Cr) film, the Fe(Cr) layers in the nanocomposite exhibited ~50% …

Magnetic And Magnetocaloric Properties Of Pr2-Xndxfe17 Ribbons, Bishnu Dahal, Parashu Kharel, Thomas Ott, Wenyong Zhang, Shah R. Valloppilly, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The structural, magnetic and magnetocaloric properties of Fe deficient Pr_2-xNd_xFe₁₇ (x = 0.5, 0.7) alloys prepared by arc-melting and melt- spinning have been investigated. The room temperature x-ray diffraction patterns show that the samples are nearly single-phase and crystallize in the rhombohedral Th₂Zn₁₇-type crystal structure. The Curie temperatures determined from the thermomagnetic curves are 302 K and 307 K for Pr_1.5Nd_0.5Fe₁₇ and Pr_1.3Nd_0.7Fe₁₇, respectively. The peak magnetic entropy change and the relative cooling power at field change of 50 kOe …

Controlling The Magnetocrystalline Anisotropy Of E-Fe2o3, Imran Ahamed, Ralph Skomski, Arti Kashyap

Nebraska Center for Materials and Nanoscience: Faculty Publications

The magnetocrystalline anisotropy of pristine and Co-substituted ε-Fe₂O₃ is investigated by density functional calculations. The epsilon-iron oxide is the only polymorph of Fe₂O₃ magnetoelectric in its antiferromagnetic ground states other crystalline forms being α-Fe₂O₃ (hematite), β-Fe₂O₃, and γ-Fe₂O₃ (maghemite). The magnetizations of the four iron sublattices are antiferromagnetically aligned with slightly different magnetic moments resulting in a ferrimagnetic structure. Compared to the naturally occurring hematite and maghemite, bulk ε-Fe₂O₃ is difficult to prepare, but ε-Fe₂O₃ nanomaterials of different …

Quantum Phase Transition And Ferromagnetism In Co1+XSn, Rabindra Pahari, Balamurugan Balasubramanian, Rohit Pathak, Manh Coung Nguyen, Shah R. Valloppilly, Ralph Skomski, Arti Kashyap, Cai-Zhuang Wang, Kai-Ming Ho, George C. Hadjipanayis, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The onset of ferromagnetism in cobalt-tin alloys is investigated experimentally and theoretically. The Co₁₊xSn alloys were prepared by rapid quenching from the melt and form a modified hexagonal NiAs-type crystal structure for 0.45 ≤ x ≤ 1. The magnetic behavior is described analytically and by density-functional theory using supercells and the coherent-potential approximation. The excess of Co concentration x, which enters the interstitial 2d sites in the hypothetical NiAs-ordered parent alloy CoSn, yields a Griffiths-like phase and, above a quantum critical point (x_c ≈ 0.65), a quantum phase …

Crystal Structure And Dzyaloshinski–Moriya Micromagnetics, Ahsan Ullah, B. Balamurugan, Wuzhang Fang, Shah R. Valloppilly, Xingzhong Li, Rabindra Pahari, Lanping Yue, Andrei Sokolov, David J. Sellmyer, Ralph Skomski

Nebraska Center for Materials and Nanoscience: Faculty Publications

The relationship between atomic-scale and micromagnetic Dzyaloshinski–Moriya (DM) interactions has been investigated. By analyzing the Lifshitz invariants for different point groups, we have found that there is no unique link between the absence of inversion symmetry and DM interactions. The absence of inversion symmetry is a necessary condition for a net DM interaction in crystals, but several noncentrosymmetric point groups have zero DM interactions. In many cases, the key consideration is whether the crystals are polar and/or chiral. For example, MnSi-type spin spirals, which violate helical spin symmetry, are caused by the insertion of chiral atomic-scale building blocks into an …

Irrigation Water Quality—A Contemporary Perspective, Arindam Malakar, Daniel D. Snow, Chittaranjan Ray

Nebraska Water Center: Faculty Publications

In the race to enhance agricultural productivity, irrigation will become more dependent on poorly characterized and virtually unmonitored sources of water. Increased use of irrigation water has led to impaired water and soil quality in many areas. Historically, soil salinization and reduced crop productivity have been the primary focus of irrigation water quality. Recently, there is increasing evidence for the occurrence of geogenic contaminants in water. The appearance of trace elements and an increase in the use of wastewater has highlighted the vulnerability and complexities of the composition of irrigation water and its role in ensuring proper crop growth, and …

High-Order Finite-Difference Nonlinear Filter Methods For Subsonic Turbulence Simulation With Stochastic Forcing, Alexei G. Kritsuk, Dmitry Kotov, Bjorn Sjögreen, Helen C. Yee

United States National Aeronautics and Space Administration: Publications

Numerical stability of high-order fi lter schemes developed by Yee & Sjogreen is tested on thr~dimensional turbulence simulations with stochastic forcing and their performance is compared with that ofTVD and \VENO schemes. The bestperforming filter method employs an eighth-order central base scheme with the Kennedy & Gruber skew-symmetric splitting of the inviscid fttLx derivative, a wavelet-based local flow sensor, a nonlinear filter utilizing the dissipative portion of seventh-order \\'ENO scheme, and an explicit third- or fourth-order RungeKutta t ime integration. \Ve show that the filter scheme is more computational]y efficient and provides a wider spectral bandwidth compared to the seventh-order …

Associated Primes And Syzygies Of Linked Modules, Olgur Celikbas, Mohammad T. Dibaei, Mohsen Gheibi, Arash Sadeghi, Ryo Takahaski

Department of Mathematics: Faculty Publications

Motivated by the notion of geometrically linked ideals, we show that over a Gorenstein local ring R, if a Cohen-Macaulay R-module M of grade g is linked to an R-module N by a Gorenstein ideal c, such that AssR(M)\AssR(N) = ;, then M R N is isomorphic to direct sum of copies of R=a, where a is a Gorenstein ideal of R of grade g + 1. We give a criterion for the depth of a local ring (R;m; k) in terms of the homological dimensions of the modules linked to the syzygies of the residue eld k. As a …

A Doubly Nonlocal Laplace Operator And Its Connection To The Classical Laplacian, Petronela Radu, Kelseys Wells

Department of Mathematics: Faculty Publications

In this paper, motivated by the state-based peridynamic frame- work, we introduce a new nonlocal Laplacian that exhibits double nonlocality through the use of iterated integral operators. The operator introduces addi- tional degrees of exibility that can allow for better representation of physical phenomena at different scales and in materials with different properties. We study mathematical properties of this state-based Laplacian, including connec- tions with other nonlocal and local counterparts. Finally, we obtain explicit rates of convergence for this doubly nonlocal operator to the classical Laplacian as the radii for the horizons of interaction kernels shrink to zero.

Drought Scenario-Based Exercises: A Research- And Experience-Based Reference Document, Deborah Bathke, Tonya Haigh, Tonya Bernadt, Nicole Wall

National Drought Mitigation Center: Publications

Contents

Acknowledgements.............................................................................. 1

Contents ................................................................................... 2

1.Introduction......................................................................................4

Objectives .............................................................................................................. 4

Format ................................................................................................................ 5

2. Drought and the Benefits of Preparation .................................................. 6

Drought Basics .................................................. 6

The Effects of Drought ................................................................................. 7

Preparing for Drought ............................................................................................... 9

Scenario Planning and Exercises ................................................................... 10

Urban Forests In A Changing Environment: Motivations For Tree Planting And Perspectives Of Climate Change Impacts On Urban Forests, Tobias Burnham

School of Natural Resources: Dissertations, Theses, and Student Research

Urban trees perform several ecosystem services important to humans. Climate variability and poor management threatens urban forests with ecological and socio-economic consequences. Therefore, it is critical urban trees are sustainably managed. For an urban tree management plan to succeed, social inputs at the residential scale must be taken into consideration. The aim of this research is to help inform urban forest managers of social variables that may play an integral role in successful implementation of urban forest management plans. Social factors behind home-owner decision-making to plant or remove trees in the Lincoln and Omaha metro areas show that 75% of …

Electrocaloric Effect In Ferroelectric Ceramics With Point Defects, Ming Wu, Qingshan Zhu, Jianting Li, Dongsheng Song, Honghui Wu, Mengyao Guo, Jinghui Gao, Yang Bai, Yujun Feng, Stephen J. Pennycoock, Xiaojie Lou

Chemistry Department: Faculty Publications

The electrocaloric effect has drawn much attention due to its potential application in cooling devices. A negative electrocaloric effect is predicted to be induced in defect-doped ferroelectrics by computational results [A. Grunebohm and T. Nishimatsu, Phys. Rev. B 93, 134101 (2016) and Ma et al., Phys. Rev. B 94, 094113 (2016)], but it need to be confirmed by experimental results. In this work, we prepared a 1mol. % Mn-doped Pb(Zr_0.2,Ti_0.8)O₃ ceramics (Pb((Zr_0.2,Ti_0.8)_0.99,Mn_0.01)O₃), and the electrocaloric effect of the defect-containing ferroelectric ceramics has …

Experimental Assessment Of Predation Risk For Juvenile Green Sturgeon, Acipenser Medirostris, By Two Predatory Fishes, S. Baird, A. E. Steel, D. E. Cocherell, Jamilynn B. Poletto, R. Follenfant, N. A. Fangue

School of Natural Resources: Faculty Publications

No abstract provided.

Pesticide Application Practices And Knowledge Among Small-Scale Local Rice Growers And Communities In Rwanda: A Cross-Sectional Study, Benjamin Ndayambaje, Hellen Amuguni, Jeanne Coffin-Schmitt, Nancy Sibo, Martin Ntawubizi, Elizabeth Vanwormer

School of Natural Resources: Faculty Publications

Background: Agriculture contributes a third of Rwanda’s GDP and is the main source of income for rural households, with 80% of the total population involved in crop and/or livestock production. The Government of Rwanda established the Muvumba rice project in 2011 amidst a policy shift towards rice as a national staple crop. However, the indiscriminate use of pesticides by local, low-income rice growers has raised concerns about potential human, animal and ecosystem health impacts as pesticide distribution and application are not strictly regulated. Although pesticide use can directly influence farmer health and ecosystems, little is known about small-scale farmers’ pesticide …

A Pilot Qualitative Case Study Of Agricultural And Natural Resources Scientists’ Twitter Usage For Engaging Public Audiences, Jaime Loizzo, Catherine Jones, Abby Steffen

School of Natural Resources: Faculty Publications

Scientists are frequently asked to broadly share their expertise and research with a variety of audiences, beyond typical academic circles in their home disciplines. That could include developing community engagement programs, school outreach, leveraging online social networks, and other activities. The purpose of this study was to examine U.S. agricultural and natural resources (ANR) scientists’ typical science communication channels, their experiences utilizing Twitter for sharing their knowledge, research, and engaging in online public science discussion. Diffusion of Innovations theory and the model of science in-reach versus outreach guided this study. Researchers used a qualitative case study design. Data collection included …

A Methodology For Flash Drought Identification: Application Of Flash Drought Frequency Across The United Statesjordan, Jordan I. Christian, Jeffrey B. Basara, Jason A. Otkin, Eric D. Hunt, Ryann A. Wakefield, Paul Flanagan, Xiangming Xiao

School of Natural Resources: Faculty Publications

With the increasing use of the term ‘‘flash drought’’ within the scientific community, Otkin et al. provide a general definition that identifies flash droughts based on their unusually rapid rate of intensi- fication. This study presents an objective percentile-based methodology that builds upon that work by identifying flash droughts using standardized evaporative stress ratio (SESR) values and changes in SESR over some period of time. Four criteria are specified to identify flash droughts: two that emphasize the vegetative impacts of flash drought and two that focus on the rapid rate of intensification. The method- ology was applied to the North …

Evaluating The Efficacy Of The Rodenatortm (Propane-Oxygen Device) For Control Of Black-Tailed Prairie Dogs In Montana, Stephen M. Vantassel

School of Natural Resources: Faculty Publications

Black-tailed prairie dogs’ feeding and burrowing behavior is a significant economic nuisance to agricultural producers. We tested the RodenatorTM on two portions of an isolated prairie dog town in Lewis and Clark County, Montana to determine how effective it was in reducing prairie dog numbers. Though other studies have been done using propane-oxygen devices, our study employed updated application techniques and an aggressive hole closing procedure to reduce the likelihood of false failures. In the southern area, we treated 53 burrows for 30 seconds with oxygen set at 40 psi and propane at 45 psi. In the northern area, we …

A Methodology For Flash Drought Identification: Application Of Flash Drought Frequency Across The United States, Jordan I. Christian, Jeffery B. Basara, Jason A. Otkin, Eric D. Hunt, Ryann A. Wakefield, Paul X. Flanagan, Xiangming Xiao

School of Natural Resources: Faculty Publications

With the increasing use of the term ‘‘flash drought’’ within the scientific community, Otkin et al. provide a general definition that identifies flash droughts based on their unusually rapid rate of intensification. This study presents an objective percentile-based methodology that builds upon that work by identifying flash droughts using standardized evaporative stress ratio (SESR) values and changes in SESR over some period of time. Four criteria are specified to identify flash droughts: two that emphasize the vegetative impacts of flash drought and two that focus on the rapid rate of intensification. The methodology was applied to the North American Regional …

An Information Theory-Based Approach To Assessing Spatial Patterns In Complex Systems, Tarsha Eason, Wen Ching-Chuang, Shana Sundstrom, Heriberto Cabezas

School of Natural Resources: Faculty Publications

Given the intensity and frequency of environmental change, the linked and cross-scale nature of social-ecological systems, and the proliferation of big data, methods that can help synthesize complex system behavior over a geographical area are of great value. Fisher information evaluates order in data and has been established as a robust and effective tool for capturing changes in system dynamics, including the detection of regimes and regime shifts. The methods developed to compute Fisher information can accommodate multivariate data of various types and requires no a priori decisions about system drivers, making it a unique and powerful tool. However, the …

Variation In White-Tailed Deer Antler Size: The Effects Of Age, Landscape Composition, And Physiographic Province, Kathleen B. Quebedeaux, Andrew R. Little, Nathan P. Nibbelink, Gino J. D'Angelo, Charlie H. Killmaster, Karl V. Miller

School of Natural Resources: Faculty Publications

Spatial variation in landscape composition can influence phenotypic expression in wildlife species and can improve management efforts to express certain phenotypic traits. We evaluated the influence of age, landscape composition, and physiographic province on white-tailed deer (Odocoileus virginianus) antler characteristics using data from 16,622 male deer (age range: 1.5–3.5+ years old) harvested between 1997–2016 across five physiographic provinces in Georgia. Age and physiographic province influenced antler size index (ASI; P < 0.001). ASI of yearling males was greatest (- x = 53.37; SE = 0.39) in the Upper Coastal Plain and least (- x = 46.23; SE = 0.51) in the Lower Coastal Plain physiographic province. Given the differences in ASI among physiographic provinces, we evaluated how landscape composition within each physiographic province influenced ASI of 7,325 yearling (1.5-year-old) males. Yearling ASI was positively related to increasing coverage of cultivated crops and suburban-urban areas (e.g., parks, small housing developments). Conversely, evergreen and deciduous forested cover consistently had a negative effect on ASI, except in the Ridge and Valley physiographic province where evergreen was positively related to ASI. Wildlife managers and hunters should recognize the effects of age, landscape composition, and physiographic province when setting antler size expectations.

Variation In White-Tailed Deer Antler Size: The Effects Of Age, Landscape Composition, And Physiographic Province., K. B. Quebedeaux, Andrew R. Little, N. P. Nibbelink, G. J. D'Angelo, C. H. Killmaster, K. V. Miller

School of Natural Resources: Faculty Publications

Spatial variation in landscape composition can influence phenotypic expression in wildlife species and can improve management efforts to express certain phenotypic traits. We evaluated the influence of age, landscape composition, and physiographic province on white-tailed deer (Odocoileus virginianus) antler characteristics using data from 16,622 male deer (age range: 1.5–3.5+ years old) harvested between 1997–2016 across five physiographic provinces in Georgia. Age and physiographic province influenced antler size index (ASI; P < 0.001). ASI of yearling males was greatest (- x = 53.37; SE = 0.39) in the Upper Coastal Plain and least (- x = 46.23; SE = 0.51) in the Lower Coastal Plain physiographic province. Given the differences in ASI among physiographic provinces, we evaluated how landscape composition within each physiographic province influenced ASI of 7,325 yearling (1.5-year-old) males. Yearling ASI was positively related to increasing coverage of cultivated crops and suburban-urban areas (e.g., parks, small housing developments). Conversely, evergreen and deciduous forested cover consistently had a negative effect on ASI, except in the Ridge and Valley physiographic province where evergreen was positively related to ASI. Wildlife managers and hunters should recognize the effects of age, landscape composition, and physiographic province when setting antler size expectations.

Environmental Controls On The Seasonal Variation In Gas Exchange And Water Balance In A Near-Coastal Mediterranean Pinus Halepensis Forest, Mariangela N. Fotelli, Evangelia Korakaki, Spyridon A. Paparrizos, Kalliopi Radoglou, Tala Awada, Andreas Matzarakis

School of Natural Resources: Faculty Publications

No abstract provided.

Tree-Ring Stable Isotopes Show Different Ecophysiological Strategies In Native And Invasive Woody Species Of A Semi-Arid Riparian Ecosystem In The Great Plains Of The United States, Tala Awada, Kristen Skolaut, Giovanna Battipaglia, Matthias Saurer, Diego A. Riveros-Iregui, Adam Schapaugh, Julie Huddle, Xinhua Zhou, Derrell Martin, Paolo Cherubini

School of Natural Resources: Faculty Publications

No abstract provided.

Nu-Spidercam: A Large-Scale, Cable-Driven, Integrated Sensing And Robotic System For Advanced Phenotyping, Remote Sensing, And Agronomic Research, Geng Bai, Yufeng Ge, David Scoby, Bryan Leavitt, Vincent Stoerger, Norbert Kirchgessner, Suat Irkmak, George Graef, James Schnable, Tala Awada

School of Natural Resources: Faculty Publications

No abstract provided.

Leveraging Image Analysis For High-Throughput Plant Phenotyping, Sruti Das Choudhury, Ashok Samal, Tala Awada

School of Natural Resources: Faculty Publications

No abstract provided.

Comment On "Derivation Of A Sigmoid Generalized Complementary Function For Evaporation With Physical Constraints" By S. Han And F. Tian, Jozsef Szilagyi, Richard D. Crago

School of Natural Resources: Faculty Publications

No abstract provided.

National Survey Of Geoscience Teaching Practices 2016: Current Trends In Geoscience Instruction Of Scientific Modeling And Systems Thinking, Diane Lally, Cory T. Forbes, Karen S. Mcneal, Nicholas A. Soltis

School of Natural Resources: Faculty Publications

No abstract provided.

Empirical Methods For Remote Sensing Of Nitrogen In Drylands May Lead To Unreliable Interpretation Of Ecosystem Function, Hamid Dashti, Nancy F. Glenn, Susan Ustin, Jessica J. Mitchell, Yi Qi, Nayani T. Ilangakoon, Alejandro N. Flores, Jose Luis Silvan-Cardenas, Kaiguang Zhao, Lucas P. Spaete, Marie-Anne De Graaff

School of Natural Resources: Faculty Publications

No abstract provided.

The Complementary Relationship (Cr) Of Evaporation: A Calibration-Free Diagnostic And Benchmarking Tool For Large-Scale Terrestrial Evapotranspiration Modeling, N. Ma, J. Szilagyi

School of Natural Resources: Faculty Publications

No abstract provided.