Physical Sciences and Mathematics Commons^™

Ecology Of Elk In The Pine Ridge Region Of Northwestern Nebraska: Seasonal Distribution, Characteristics Of Wintering Sites, And Herd Health, Michael A. Cover

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

No abstract provided.

Water Current, Volume 32, No. 4, August 2000

Water Current Newsletter

New Method for Detecting Trace Amounts of MTBE and Ethanol at Heart of UNL Contamination Research
From the Director: New Director, New Directions, New Challenges
Lawn and Garden Drought and Climate Tolerance Are Focus of Festival of Color
Summer 2000 Water and Natural Resources Tour
Re-Cap of Water Management Issues Available Free
See You at Husker Harvest Days
NDEQ Water Quality Monitoring
Center-Pivot Map Available

The Development Of A Lutetium Recovery Plant, Peter Michael Smith

Doctoral Dissertations

This research project focused on the scale-up of an industrial facility for the continuous counter-current solvent extraction (CCCSX) separation of lutetium. CCCSX involves a multistage apparatus for the mixing in each stage of two immiscible liquid phases to transfer an analyte from one phase to the other. The two phases continuously flow in opposite directions in a CCCSX system. In this research, aqueous lutetium solutions, obtained from the acid leaching of lutetium oxyorthosilicate, were mixed with kerosene solutions of phosphorus based metal extractants (e.g. mono-2-ethylhexyl-(2- ethylhexyl) phosphonic acid, MEHEHP). This system extracted the lutetium from the aqueous phase, transferring the …

Laser Spark Ignition Modeling, Ivan George Dors

Doctoral Dissertations

Laser spark phenomena are studied in air and ammonia-oxygen mixtures by the use of a two-dimensional, axially-symmetric, time-accurate computational fluid dynamic model. The initial laser spark temperature distribution is generated to simulate a post-breakdown profile that is consistent with theoretical, experimental, and computational investigations for a nominal 10-ns optical breakdown laser pulse. Thermodynamic properties of various species are extended to 35,000 K to cover the range of the initial temperature distribution. The developed computational model includes a kinetics mechanism that implements plasma equilibrium kinetics in ionized regions.

The computational model time-accurately predicts species concentrations, free electron number density decay, blast …

The Narrow-Line Region In The Seyfert 2 Galaxy Ngc 3393, Andrew J. Cooke, J. A. Baldwin, Gary J. Ferland, Hagai Netzer, Andrew S. Wilson

Physics and Astronomy Faculty Publications

The narrow-line region (NLR) of the Seyfert 2 galaxy NGC 3393 is dominated by a symmetric structure which appears as S-shaped arms in Hubble Space Telescope (HST) images. These arms, which occupy the central few arcseconds of the nucleus, border a linear, triple-lobed radio source. We use HST imaging and spectra, ground-based optical images, long-slit spectra, Fabry-Perot imaging spectroscopy, and VLA radio data to perform a detailed investigation of the kinematics and ionization of the line-emitting gas in NGC 3393 and of its relationship with the relativistic gas responsible for the radio emission. The excitation map [O III] …

Magnetic Localization In Transition-Metal Nanowires, Ralph Skomski, H. Zeng, M. Zheng, David J. Sellmyer

David Sellmyer Publications

Magnetization reversal in transition-metal nanowires is investigated. Model calculations explain why magnetization reversal is localized, as opposed to the sometimes assumed delocalized coherent-rotation and curling modes. The localization is a quite general phenomenon caused by morphological inhomogenities and occurring in both polycrystalline and single-crystalline wires. In the polycrystalline limit, the competition between interatomic exchange and anisotropy gives rise to a variety of random-anisotropy effects, whereas nearly single-crystalline wires exhibit a weak localization of the nucleation mode. Model predictions are used to explain the coercive and magnetic-viscosity behavior of Co (and Ni) nanowires electrodeposited in self-assembled alumina pores.

Effect Of Disorder On Perpendicular Magnetotransport In Co/Cu Multilayers, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

We investigate the spin-dependent conductance of the Co/Cu multilayers in the current-perpendicular-tothe- plane (CPP) geometry. Using a realistic tight-binding model for the electronic band structure of the multilayer, and introducing disorder in the on-site atomic energies we calculate the conductance and giant magnetoresistance (GMR) within the quantum-mechanical linear response theory by performing averaging over random disorder configurations. By varying the thickness and the number of individual layers and the degree of disorder in the multilayers, we analyze factors influencing the CPP GMR. In particular, we show the importance of the thickness-dependent interface resistance, which depends on the mean free path …

Theory Of Magnetostatic Coupling In Thin-Film Rectangular Magnetic Elements, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

A theory of magnetostatic coupling in thin-film uniformly magnetized arrays of rectangular magnetic elements is presented. Analytic expressions for the magnetostatic energy and the dipolar fields are derived. The influence of the aspect ratio and the spacing between the elements on the magnetostatic coupling is investigated. It is found that increasing the aspect ratio reduces the critical distance between the elements, above which the magnetostatic inter-element coupling can be neglected.

Measuring The "Managedness" And Covered Benefits Of Health Plans, Paula Diehr, David Grembowski

Paula Diehr

STUDY AIMS: (1) To develop indexes measuring the degree of managedness and the covered benefits of health insurance plans, (2) to describe the variation in these indexes among plans in one health insurance market, (3) to assess the validity of the health plan indexes, and (4) to examine the association between patient characteristics and the health plan indexes. Measures of the "managedness" and covered benefits of health plans are requisite for studying the effects of managed care on clinical practice and health system performance, and they may improve people's understanding of our complex health care system. DATA SOURCES/STUDY SETTING: As …

De-2 Observations Of Morningside And Eveningside Plasma Density Depletions In The Equatorial Ionosphere, M. Palmroth, H. Laakso, Bela G. Fejer, R. F. Pfaff

Bela G. Fejer

The occurrence of equatorial density depletions in the nightside F region ionosphere has been investigated by using observations gathered by the polar-orbiting Dynamics Explorer 2 satellite from August 1981 to February 1983. A variety of electric field/plasma drift patterns were observed within these depletions, including updrafting, downdrafting, bifurcating, converging, subsonic, and supersonic flows. The depletions, 116 events in total, are distributed over two groups: group I (eveningside depletions) consists of the events in the 1900–2300 MLT sector, and group II (morningside depletions) are the events in the 2300–0600 MLT sector. A statistical analysis reveals clear differences in the density depletion …

Dynamics Of Lattice Kinks, Panos Kevrekidis, M. I. Weinstein

Panos Kevrekidis

In this paper we consider two models of soliton dynamics (the sine Gordon and the \phi^4 equations) on a 1-dimensional lattice. We are interested in particular in the behavior of their kink-like solutions inside the Peierls- Nabarro barrier and its variation as a function of the discreteness parameter. We find explicitly the asymptotic states of the system for any value of the discreteness parameter and the rates of decay of the initial data to these asymptotic states. We show that genuinely periodic solutions are possible and we identify the regimes of the discreteness parameter for which they are expected to …

9. Oskar Friedrich Olaj, Otto Vogl

Otto Vogl

No abstract provided.

Two-Level Atom In An Optical Parametric Oscillator: Spectra Of Transmitted And Fluorescent Fields In The Weak Driving Field Limit, James P. Clemens, Perry R. Rice, Pranaw Kumar Rungta, Robert J. Brecha

Physics Faculty Publications

We consider the interaction of a two-level atom inside an optical parametric oscillator. In the weak-driving-field limit, we essentially have an atom-cavity system driven by the occasional pair of correlated photons, or weakly squeezed light. We find that we may have holes, or dips, in the spectrum of the fluorescent and transmitted light. This occurs even in the strong-coupling limit when we find holes in the vacuum-Rabi doublet. Also, spectra with a subnatural linewidth may occur. These effects disappear for larger driving fields, unlike the spectral narrowing obtained in resonance fluorescence in a squeezed vacuum; here it is important that …

Spectroscopy And Photometry Of Nearby Young Solar Analogs, Eric J. Gaidos, Gregory W. Henry, Stephen M. Henry

Information Systems and Engineering Management Research Publications

We present new photometry and spectroscopy of 34 stars from a catalog of 38 nearby (d < 25 pc) G and K dwarfs selected as analogs to the early Sun. We report that the least active star in our sample is also slowly rotating and probably of solar age. Two other stars appear to be evolved objects that have recently acquired angular momentum. A fourth star may be a spectroscopic binary. Many of the other stars belong to previously identified common proper-motion groups. Space motions, lithium abundances, and Ca II emission of these stars suggest ages between 70 and 800 Myr.

Association Of Energetic Neutral Atom Bursts And Magnetospheric Substorms, A. M. Jorgensen, L. Kepko, M. G. Henderson, Harlan E. Spence, G. D. Reeves, J. B. Sigwarth, L. A. Frank

Physics & Astronomy

No abstract provided.

Release Of No(X) From Sunlight-Irradiated Midlatitude Snow, R E. Honrath, Matthew C. Peterson, M P. Dziobak, Jack E. Dibb, Matthew Arsenault, S A. Green

Earth Sciences

Photochemical production and release of gas-phase NO(x) (NO + NO2) from the natural snowpack at a remote site in northern Michigan were investigated during the Snow Nitrogen and Oxidants in Winter study in January 1999. Snow was collected in an open 34 L chamber, which was then sealed with a transparent Teflon cover and used as an outdoor flow and reaction chamber. Significant increases in NO(x) mixing ratio were observed in synthetic and ambient air pulled through the sunlit chamber. [NO(x)] enhancements were correlated to ultraviolet sunlight intensity, reaching ~300 pptv under partially overcast midday, mid-winter conditions. These findings are …

On The Effectiveness Of Probabilistic Packet Marking For Ip Traceback Under Denial Of Service Attack, Kihong Park, Heejo Lee

Department of Computer Science Technical Reports

No abstract provided.

Strain Variation With Sample Thickness In Gan Grown By Hydride Vapor Phase Epitaxy, D. C. Reynolds, David C. Look, B. Jogai, J. E. Hoelscher, R. E. Sherriff, Richard J. Molnar

Physics Faculty Publications

High quality GaN crystals can be grown on sapphire by hydride vapor phase epitaxy. The thermal expansion mismatch between sapphire and GaN produces strain in the GaN crystal as it is cooled from the growth temperature to room temperature. The strain is evidenced by shifts in the photoluminescence and reflectance line positions. By analyzing the surface strain as the crystal thickness is increased, the thickness required to obtain zero surface strain can be estimated. This structure might provide a lattice matched and thermally matched substrate for further epitaxial growth of GaN.

Oslo Summer Workshop On Stochastic Analysis, Salah-Eldin A. Mohammed

Miscellaneous (presentations, translations, interviews, etc)

No abstract provided.

Fundamentals Of Economic Principles And Wildlife Management, Peter W. Schuhmann, Kurt A. Schwabe

Human Conflicts with Wildlife: 2002 Symposium

This paper presents an overview of the economic fundamentals involved in wildlife management, with special consideration for cases involving harmful wildlife-human interactions. The process of benefit-cost analysis is used as a unifying platform for incorporating both theoretical and empirical issues. Topics such as external market effects and public goods are detailed in order to give the reader a theoretical foundation for understanding the economic perspective on the problems associated with defining and attaining optimally managed wildlife populations. To these principles we add practical considerations for measuring the costs and benefits associated with wildlife populations. Different categories of wildlife values, such …

Damage Abatement And Compensation Programs As Incentives For Wildlife Management On Private Land, Jonathan K. Yoder

Human Conflicts with Wildlife: 2002 Symposium

Public damage abatement and compensation programs may be used to alter private incentives for damage abatement and habitat provision. A model is developed that explains the economic logic behind prevalent characteristics of public wildlife damage programs. The model is supported with an examination of a broad cross-section of wildlife agency policy and law. The model can be used by wildlife managers and policy makers as a conceptual framework for understanding the incentive effects of compensation and abatement policy.

The Endangered Species Act And Private Landowner Incentives, Jeffrey A. Michael

Human Conflicts with Wildlife: 2002 Symposium

While intended to increase the habitat available to endangered species, the restrictions of the Endangered Species Act (ESA) increase the costs of harboring an endangered species to private landowners and create incentives for private landowners to reduce habitat. This paper illustrates the incentive for habitat destruction with a simple model of private land use under the ESA, and uses it to predict the effects of changes in policy or biological conditions on private landowner incentives. Many anecdotal accounts and recent empirical research support the predictions of the model. Because of the ESA’s perverse incentives, many have proposed replacing the punitive …

Economic Considerations Of Damage Assessment, Richard M. Engeman

Human Conflicts with Wildlife: 2002 Symposium

Cost-effectiveness is the fundamental economic test of any damage control or damage mitigation strategy, and damage assessment is the essential component for determination of cost-effectiveness. However, there are many potential costs associated with making damage assessments. The sampling and measurement required to produce a damage assessment have associated effort and costs, but even greater costs can be incurred due to inappropriate management decisions resulting from inaccurate damage assessments. Other costs can result from using an assessment method that is unsuited to management objectives, or by misinterpreting or not understanding the relationship between observed damage and actual losses. The concepts of …

Spreadsheets, Response Surfaces, And Intervention Decisions In Wildlife Damage Management, Ray T. Sterner

Human Conflicts with Wildlife: 2002 Symposium

An a priori approach to examining the economics of performing management activities to reduce agricultural and resource damage by wildlife is described. Computer spreadsheet procedures are used to derive response surfaces of potential net savings and benefit:cost indices for selected crop- or resource-protection activities. Tabular and graphical displays of these indices afford decision-making aids for wildlife-damage interventions. An example based on the use of an acute rodenticide, zinc phosphide (Zn₃P₂), for vole (Microtus spp.) control in alfalfa (Medicago sativa) is described. Iterative calculations were derived for 1,260 possible combinations of 3 field-size, 6 …

Impacts Of House Mice On Crops In Australia - Costs And Damage, Peter R. Brown, Grant R. Singleton

Human Conflicts with Wildlife: 2002 Symposium

Rodents cause serious losses to crops in many different parts of the world. The house mouse (Mus domesticus, Schwarz and Schwarz 1943) is a serious pest to agriculture in Australia. The impacts of house mouse damage to crops in Australia were examined. Plagues of mice (>1,000 mice/ha) cause enormous economic and social stress to rural communities in Australia. The mouse plague in 1993/94 caused about US$60 million in damage to crops, intensive livestock industries, and rural communities. The impact of mouse plagues is generally well understood, but there is a dearth of knowledge about the relationship between …

Development Of A Model To Assess Rodent Control In Swine Facilities, Kurt C. Vercauteren, Scott E. Hygnstrom, Robert M. Timm, Robert M. Corrigan, John Beller, Larry L. Bitney, Michael C. Brumm, Daniel Meyer, Dallas R. Virchow, Robert W. Wills

Human Conflicts with Wildlife: 2002 Symposium

At the request, and with the support, of the National Pork Producers Council we are conducting a comprehensive economic analysis of rodent control in swine production facilities. The authors represent an interdisciplinary working group that has been assembled to identify all necessary input variables and values associated with rodent damage and control. The working group consists of specialists in swine production, facilities management, agricultural economics, swine health, rodent control, the pest management industry, systems modeling, and distance education. We incorporated data from the scientific literature and personal experience into an interactive STELLA systems model. The model generates benefit-cost analyses and …

Using Bioeconomic Models To Maximize Benefits From Vertebrate Pest Control: Lamb Predation By Feral Pigs, David Choquenot, Jim Hone

Human Conflicts with Wildlife: 2002 Symposium

The question “When should investment in pest control stop?” either explicitly or implicitly underpins decisions concerning pest control made at every level of enterprise or government, regardless of whether these decisions are tactical or strategic. Bioeconomic modeling provides a quantitative framework for considering the benefits and costs of alternative pest control strategies. In this case study, we develop 3 bioeconomic models that examine strategies based on helicopter shooting and 1080 poisoning, for reducing feral pig (Sus scrofa) predation of newborn lambs in wool-growing enterprises located in Australia’s rangelands. In the first model, marginal analysis indicated that helicopter shooting …

Economics Of Predation Management In Relation To Agriculture, Wildlife, And Human Health And Safety, Michael J. Bodenchuk, J. Russell Mason, William C. Pitt

Human Conflicts with Wildlife: 2002 Symposium

Predation management is controversial and much recent debate has focused on the cost of management efforts. This manuscript considers the cost of predators to agriculture, big game or threatened and endangered species management, and human health and safety. Subsequently, the cost of efforts to manage predation in these contexts is discussed, and benefit:cost ratios are calculated. When properly applied, predation management shows benefit:cost ratios of between 3:1 to 27:1 for agriculture and 2:1 to 22:1 for wildlife protection. For human health and safety, benefit:cost ratios are more difficult to calculate, but we argue that benefits outweigh costs in many different …

An Analysis Of Deer-Vehicle Collisions: The Case Of Ohio, Kurt A. Schwabe, Peter W. Schuhmann, Michael J. Tonkovich, Ellen Wu

Human Conflicts with Wildlife: 2002 Symposium

The costs of deer-vehicle collisions (DVCs) in Ohio are estimated to be in excess of US$52 million annually. The intention of this paper is to identify factors contributing to the abundance of DVCs in Ohio, calculate the average cost of a deer-vehicle collision event, and illustrate the potential gains in economic efficiency from alternative approaches for reducing DVCs. Our results suggest that large potential economic gains from reducing DVCs in Ohio exist and that the optimal strategies for achieving these reductions seem to combine both changes in deer management schemes and deer-vehicle mitigation strategies.

The Economics Of Managing Belding’S Ground Squirrels In Alfalfa In Northeastern California, Desley A. Whisson, Steve B. Orloff, Donald L. Lancaster

Human Conflicts with Wildlife: 2002 Symposium

We used estimates of yield loss from 1995 to 1999 and the reported costs and effectiveness of available control methods to provide a basis for developing a cost-effective management strategy for Belding’s ground squirrels in alfalfa in northern California. Mean annual losses varied between US$110/ha and US$300/ha of alfalfa. Growers usually spend less than US$25/ha on control methods that are implemented haphazardly and provide poor control. We suggest that growers can afford to spend more on control methods such as burrow fumigation or exclusion fencing that previously have been viewed as being too expensive. Control efforts should be focused on …