Physical Sciences and Mathematics Commons^™

Robust Isothermal Electric Control Of Exchange Bias At Room Temperature, Xi He, Ning Wu, Anthony N. Caruso, Elio Vescovo, Kirill D. Belashchenko, Peter A. Dowben, Christian Binek

Kirill Belashchenko Publications

Voltage-controlled spin electronics is crucial for continued progress in information technology. It aims at reduced power consumption, increased integration density and enhanced functionality where non-volatile memory is combined with highspeed logical processing. Promising spintronic device concepts use the electric control of interface and surface magnetization. From the combination of magnetometry, spin-polarized photoemission spectroscopy, symmetry arguments and first-principles calculations, we show that the (0001) surface of magnetoelectric Cr₂O₃ has a roughness-insensitive, electrically switchable magnetization. Using a ferromagnetic Pd/Co multilayer deposited on the (0001) surface of a Cr₂O₃ single crystal, we achieve reversible, room-temperature isothermal switching …

Polarized Neutron Reflectometry Study Of The Magnetization Reversal Process In Yba2cu3o7 /La2/3ca1/3mno3 Superlattices Grown On Srtio3 Substrates, J. Hoppler, H. Fritzsche, V. K. Malik, J. Stahn, G. P. Cristiani, H.-U. Habermeier, M. Rössle, Jan Honolka, Axel Enders, C. Bernhard

Axel Enders Publications

Using polarized neutron reflectometry we investigated the reversal of the magnetization of a high-T_c superconductor/ferromagnet superlattice that consists of eight bilayers of YBa₂Cu₃O₇(25.6 nm) /La_2/3Ca_1/3MnO₃(25.6 nm) grown on a SrTiO3 substrate. The measurements were performed during a magnetization hysteresis loop at 5 K. We obtained evidence that the reversal in the vicinity of the coercive field proceeds via the switching of micrometer-sized magnetic domains that are considerably larger than the typical domains of La_2/3Ca_1/3MnO₃. Furthermore, these large magnetic domains …

Dissociative Electron Attachment In Nonplanar Chlorocarbons With Π*/Σ*-Coupled Molecular Orbitals, Kayvan Aflatooni, Gordon A. Gallup, Paul Burrow

Paul Burrow Publications

Total absolute cross sections for the dissociative electron attachment (DEA) process are reported for a series of nonplanar ethylenic and phenylic compounds monosubstituted with (CH₂)_nCl groups, where n=1–4. Coupling between the local π^* molecular orbitals provided by the unsaturated moieties and the σ^* (C-Cl) orbital is thus examined as a function of the separation of these groups. In particular, the coupling is viewed from the perspective of the interacting temporary negative ions formed by short lived occupation of these orbitals and their decay into the DEA channel. A theoretical treatment of “remote” bond breaking, …

Piezoelectric Tuning Of Exchange Bias In A Batio3/Co/Coo Heterostructure, Srinivas Polisetty, W. Echtenkamp, Keith Jones, X. He, Sarbeswar Sahoo, Christian Binek

Christian Binek Publications

Piezoelectrically controlled strain is used for electric tuning of exchange-bias fields. A generic exchange-bias Co/CoO bilayer is deposited on the surface of a ferroelectric and thus piezoelectric BaTiO₃ substrate which allows to apply electrically and thermally tunable stress in the adjacent ferromagnetic Co thin film. The stress-induced strain alters foremost the magnetic anisotropy of the Co film and by that the magnetization orientation at the Co/CoO interface modifying the exchange-bias field. This results in a pronounced electrically induced weakening of the exchange bias but also includes the possibility of tuning the exchange-bias field through a subtle sign change from …

Vibrational Properties Of Ferroelectric Β-Vinylidene Fluoride Polymers And Oligomers, Serge M. Nakhmanson, Rafal Korlacki, J. Travis Johnston, Stephen Ducharme, Zhongxin Ge, James M. Takacs

Stephen Ducharme Publications

We utilize a plane-wave density-functional theory approach to investigate the vibrational properties of the all-trans ferroelectric phase of poly(vinylidene fluoride) (β-PVDF) showing that its stable state corresponds to the Ama2 structure with ordered dihedral tilting of the VDF monomers along the polymer chains. We then combine our theoretical analysis with IR spectroscopy to examine vibrations in oligomer crystals that are structurally related to the β-PVDF phase. We demonstrate that these materials—which can be grown in a highly crystalline form—exhibit IR activity similar to that of β-PVDF, making them an attractive choice for the studies of electroactive phenomena and phase transitions …

Why Ferroelectric Polyvinylidene Fluoride Is Special, Matt Poulsen, Stephen Ducharme

Stephen Ducharme Publications

Ferroelectric polymers entail a number of constraints, which together limit the useful compositional variations. These constraints include the following: a stable molecular dipole moment, compact crystal structure, conformational flexibility, and minimal steric hindrance. They are well satisfied by the prototype ferroelectric polymer, polyvinylidene fluoride, and yet almost every other conceivable molecular structure is limited by comparison.

Probing Equilibrium By Nonequilibrium Dynamics: Aging In Co/Cr Superlattices, Tathagata Mukherjee, M. Pleimling, Christian Binek

Christian Binek Publications

Magnetization relaxation is investigated in a structurally ordered magnetic Co/Cr superlattice. Tailored nanoscale periodicity creates mesoscopic spatial magnetic correlations with slow relaxation dynamics when quenching the system into a nonequilibrium state. Magnetization transients are measured after exposing the heterostructure to a magnetic set field for various waiting times. Scaling analysis reveals an asymptotic powerlaw behavior in accordance with a full aging scenario. The temperature dependence of the relaxation exponent shows pronounced anomalies at the equilibrium phase transitions of the antiferromagnetic superstructure and the ferromagnetic to paramagnetic transition of the Co layers. The latter leaves only weak fingerprints in the equilibrium …

Ab Initio Calculations And Ellipsometry Measurements Of The Optical Properties Of The Layered Semiconductor In4Se3, L. Makinistian, E. A. Albanesi, N. V. Gonzalez Lemus, A. G. Petukhov, D. Schmidt, Eva Schubert, M. Schubert, Yaroslav B. Losovyj, P. Galiy, Peter A. Dowben

Peter Dowben Publications

In this work, we present a thorough study of the optical properties of the layered orthorhombic compound In₄Se₃. The dielectric function—real and imaginary parts, the complex refraction index, the reflectivity, the absorption coefficient, and the conductivity of In₄Se₃ were calculated with the inclusion of the spin-orbit interaction, using an ab initio FP-LAPW method based on DFT. Also, generalized ellipsometry was employed for more precise measurement of the anisotropic dielectric functions for polarization along crystal a, b, and c axes of orthorhombic absorbing In₄Se₃ single crystals cut approximately parallel to …

The Local Structure Of Transition Metal Doped Semiconducting Boron Carbides, Jing Liu, Guangfu Luo, Wai-Ning Mei, Orhan Kizilkaya, Eric D. Shepherd, Jennifer I. Brand, Peter A. Dowben

Peter Dowben Publications

Transition metal doped boron carbides produced by plasma enhanced chemical vapour deposition of orthocarborane (closo-1,2-C₂B₁₀H₁₂) and 3d metal metallocenes were investigated by performing K-edge extended x-ray absorption fine structure and x-ray absorption near edge structure measurements. The 3d transition metal atom occupies one of the icosahedral boron or carbon atomic sites within the icosahedral cage. Good agreement was obtained between experiment and models for Mn, Fe and Co doping, based on the model structures of two adjoined vertex sharing carborane cages, each containing a transition metal. The local spin configurations of all …

Double Parton Interactions In Γ = 3 Jet Events In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We have used a sample of γ + 3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 to determine the fraction of events with double parton scattering (f_DP) in a single pp collision at √s = 1.96 TeV. The DP fraction and effective cross section (τ_eff ), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p_T) jet transverse momentum p^jet2_T within the range 15 ≤ p^jet2_T ≤ …

Search For Higgs Boson Production In Dilepton And Missing Energy Final States With 5.4 Fb-1 Of Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

A search for the standard model Higgs boson is presented using events with two charged leptons and large missing transverse energy selected from 5.4 fb^-1 of integrated luminosity in pp collisions at √s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron collider. No significant excess of events above background predictions is found, and observed (expected) upper limits at 95% confidence level on the rate of Higgs boson production are derived that are a factor of 1.55 (1.36) above the predicted standard model cross section at m_H = 165 GeV.

Combination Of Tevatron Searches For The Standard Model Higgs Boson In The W+W- Decay Mode, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W⁺W^-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb^-1 of pp collisions at √s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162–166 GeV at the 95% C.L.

Resource Selection By Elk In An Agro-Forested Landscape Of Northwestern Nebraska, David M. Baasch, Justin W. Fischer, Scott E. Hygnstrom, Kurt C. Vercauteren, Andrew J. Tyre, Joshua J. Millspaugh, James W. Merchant, Jerry D. Volesky

School of Natural Resources: Faculty Publications

In recent years, elk have begun recolonizing areas east of the Rocky Mountains that are largely agroforested ecosystems composed of privately owned land where management of elk is an increasing concern due to crop and forage depredation and interspecific disease transmission. We used a Geographic Information System, elk use locations (n = 5013), random locations (n = 25,065), discrete-choice models, and information-theoretic methods to test hypotheses about elk resource selection in an agro-forested landscape located in the Pine Ridge region of northwestern Nebraska, USA. Our objectives were to determine landscape characteristics selected by female elk and identify publicly owned land …

Seroprevalence Of Equine Influenza Virus In Northeast And Southern Mexico, B. J. Blitvich, L. A. Ibarra-Juarez, A. J. Cortes-Guzman, J. J. Root, A. B. Franklin, H. J. Sullivan, I. Fernandez-Salas

United States Department of Agriculture Wildlife Services: Staff Publications

EQUINE influenza A virus (EIV) is a highly infectious respiratory pathogen of horses (Hannant and Mumford 1996, Palese and Shaw 2007). The illness is characterized by an abrupt onset of fever, depression, coughing and nasal discharge, and is often complicated by secondary bacterial infections that can lead to pneumonia and death. Two subtypes of EIV, H3N8 and H7N7, have been isolated. The H7N7 subtype was first isolated from a horse in Czechoslovakia in 1956 (Prague/56), and the H3N8 subtype was first isolated from a horse in Miami in 1963 (Sovinova and others 1958, Waddell and others 1963). The last confirmed …

Temporal Variation In Terrestrial Invertebrate Consumption By Laughing Gulls In New York, Glen E. Bernhardt, Lisa Kutschbach-Brohl, Brian E. Washburn, Richard Chipman, Laura Francoeur

United States Department of Agriculture Wildlife Services: Staff Publications

Laughing gulls (Larus atricilla) are commonly found in many areas of North America and little is known about their diet, particularly in coastal-urban interfaces where gull-aircraft collisions can be a serious concern. The objective of this study was to describe and quantify the consumption of terrestrial invertebrates by laughing gulls at a coastal-urban interface in the northeastern United States. We examined the stomach contents of laughing gulls (n = 1053) collected during wildlife damage management operations at John F. Kennedy International Airport during the summers of 2003 and 2004. Terrestrial invertebrates consumed by laughing gulls represented 2 taxonomic …

Using A Cost-Effectiveness Model To Determine The Applicability Of Ovocontrol G To Manage Nuisance Canada Geese, Joe Caudell, Stephanie A. Shwiff, Michael Slater

United States Department of Agriculture Wildlife Services: Staff Publications

OvoControl G is a relatively new product that reduces hatchability of Canada goose (Branta canadensis) eggs, and few data are available on its cost effectiveness. Variables such as presence of nontargets, alternative foods, and public support can affect cost efficacy. We present a model that uses these and other factors to estimate the cost of application of OvoControl G for managing nuisance Canada geese. We found that at low goose densities (<35 pairs of geese), fixed labor was a significant portion of costs. As goose densities increase, OvoControl G becomes more cost effective than other methods, such as egg oiling or addling. Managers can use this model to determine whether OvoControl G will provide a successful and cost-effective treatment for population control of Canada geese in specific management areas.

Reproductive Biology Of Male Brown Treesnakes (Boiga Irregularis) On Guam, Tom Mathies, John A. Cruz, Valentine A. Lance, Julie A. Savidge

United States Department of Agriculture Wildlife Services: Staff Publications

Reproductive biology of males in the Guam population of the Brown Treesnake, Boiga irregularis, was investigated through monthly examinations of the urogenital system organs and plasma testosterone levels. All males examined during the 12 consecutive months of the study were spermatogenic and had sperm in the ductus epididymis and ductus deferens. No evidence of testicular recrudescence or regression was observed. Testis mass did not vary among months. Epithelial height of the kidney sexual segment was the only feature examined that varied significantly among months, with lowest heights observed in May through July. Despite this variation, the sexual segment in all …

Contraceptive Efficacy Of A Novel Intrauterine Device (Iud) In White-Tailed Deer, Karl D. Malcolm, Timothy R. Van Deelen, David Drake, Darrel J. Kesler, Kurt C. Vercauteren

United States Department of Agriculture Wildlife Services: Staff Publications

Overabundant white-tailed deer (Odocoileus virginianus) pose risks to property, health, and safety of human beings. Public concerns about lethal management can impair efforts to address these issues, particularly in urban settings. Several techniques developed for reducing reproductive output of deer have limited utility because they require repeated dosing to achieve permanent effect and face uncertain regulatory approval for use beyond experimentation. From 10 August 2006 through 30 December 2007, we evaluated the contraceptive efficacy of copper-containing intrauterine devices (IUDs) implanted trans-cervically in white-tailed deer at the E.S. George Reserve in Pinckney, Michigan. Intrauterine devices were implanted before (n …

Acetaminophen As An Oral Toxicant For Nile Monitor Lizards (Varanus Niloticus) And Burmese Pythons (Python Molurus Bivittatus), Richard E. Mauldin, Peter J. Savarie

United States Department of Agriculture Wildlife Services: Staff Publications

Context. Invasive species are a growing global problem. Biological invasions can result in numerous harmful impacts on local ecologies, and non-native herpetofauna are frequently ignored. Nile monitor lizards (Varanus niloticus) and Burmese pythons (Python molurus bivittatus, recently reassessed as Python bivittatus bivittatus), have become established in southern Florida. Both are large, semi-aquatic predators that pose serious threats to a variety of threatened and endangered species, as well as to the unique ecology of the area.

Aims. Acetaminophen (CAS#103-90-2), a lethal oral toxicant for the invasive brown treesnake (Boiga irregularis) on Guam, was investigated …

Seeking A Second Opinion: Uncertainty In Disease Ecology, Brett T. Mcclintock, James D. Nichols, Larissa L. Bailey, Darryl I. Mackenzie, William. L. Kendall, Alan B. Franklin

United States Department of Agriculture Wildlife Services: Staff Publications

Analytical methods accounting for imperfect detection are often used to facilitate reliable inference in population and community ecology. We contend that similar approaches are needed in disease ecology because these complicated systems are inherently difficult to observe without error. For example, wildlife disease studies often designate individuals, populations, or spatial units to states (e.g., susceptible, infected, post-infected), but the uncertainty associated with these state assignments remains largely ignored or unaccounted for. We demonstrate how recent developments incorporating observation error through repeated sampling extend quite naturally to hierarchical spatial models of disease effects, prevalence, and dynamics in natural systems. A highly …

Synchronous Monitoring Of Vulture Movements With Satellite Telemetry And Avian Radar, Robert C. Beason, J. S. Humphrey, N. E. Myers, Michael L. Avery

United States Department of Agriculture Wildlife Services: Staff Publications

Radar and satellite global positioning system-platform transmitter terminal (GPSPTT) transmitters provide complementary information on the movements and behaviors of individual birds. The GPS-PTT tag provides a snapshot of altitude and location of a specific individual of an identified species at predefined intervals. The history of the individual is known because each transmitter has a unique identification code. The radar cannot identify individuals or even species but it provides continuous position reports (altitude and location) of birds within its detection range. By integrating data from the two sources, the behavior and movements of identified individuals (not possible with radar) can be …

Metastability And Plasticity In A Conceptual Model Of Neurons, Bo Deng

Department of Mathematics: Faculty Publications

For a new class of neuron models we demonstrate here that typical membrane action potentials and spike-bursts are only transient states but appear to be asymptotically stable; and yet such metastable states are plastic — being able to dynamically change from one action potential to another with different pulse frequencies and from one spike-burst to another with different spike-per-burst numbers. The pulse and spike-burst frequencies change with individual ions’ pump currents while their corresponding metastable-plastic states maintain the same transmembrane voltage and current profiles in range. It is also demonstrated that the plasticity requires two one-way ion pumps operating in …

Bass’ Nk Groups And Cd H-Fibrant Hochschild Homology, G. Cortiñas, C. Haesemeyer, Mark E. Walker, C. Weibel

Department of Mathematics: Faculty Publications

The K-theory of a polynomial ring R[t ] contains the K-theory of R as a summand. For R commutative and containing Q, we describe K∗(R[t ])/K∗(R) in terms of Hochschild homology and the cohomology of Kähler differentials for the cdh topology.

We use this to address Bass’ question, whether K_n(R) = K_n(R[t ]) implies K_n(R) = K_n(R[t₁, t₂]). The answer to this question is affirmative when R is essentially of …

To The Ice: George Bird Grinnell's 1887 Ascent Of Grinnell Glacier, Richard Vaughan

Articles by Maurer Faculty

This article discusses a climbing expedition undertaken by U.S. conservationist George Bird Grinnell to ascend what would come to be known as Grinnell Glacier in Montana. Grinnell’s efforts to establish Glacier National Park are detailed. Grinnell’s previously unpublished descriptions of the glacier and its surrounding area are analyzed by the author.

Synthesis Of Satellite (Modis), Aircraft (Icartt), And Surface (Improve, Epa‐Aqs, Aeronet) Aerosol Observations Over Eastern North America To Improve Modis Aerosol Retrievals And Constrain Surface Aerosol Concentrations And Sources, Easan Drury, Daniel J. Jacob, Robert J. D. Spurr, Jun Wang, Yohei Shinozuka, Bruce E. Anderson, Antony D. Clarke, Jack Dibb, Cameron Mcnaughton, Rodney Weber

Department of Earth and Atmospheric Sciences: Faculty Publications

We use an ensemble of satellite (MODIS), aircraft, and ground‐based aerosol observations during the ICARTT field campaign over eastern North America in summer 2004 to (1) examine the consistency between different aerosol measurements, (2) evaluate a new retrieval of aerosol optical depths (AODs) and inferred surface aerosol concentrations (PM_2.5) from the MODIS satellite instrument, and (3) apply this collective information to improve our understanding of aerosol sources. The GEOS‐Chem global chemical transport model (CTM) provides a transfer platform between the different data sets, allowing us to evaluate the consistency between different aerosol parameters observed at different times and …

Linear Programming Models For Multi-Channel P2p Streaming Systems, Miao Wang, Lisong Xu, Byrav Ramamurthy

School of Computing: Conference and Workshop Papers

Most of the commercial P2P video streaming deployments support hundreds of channels and are referred to as multichannel systems. Measurement studies show that bandwidth resources of different channels are highly unbalanced and thus recent research studies have proposed various protocols to improve the streaming qualities for all channels by enabling cross-channel cooperation among multiple channels. However, there is no general framework for comparing existing and potential designs for multi-channel P2P systems. The goal of this paper is to establish tractable models for answering the fundamental question in multi-channel system designs: Under what circumstances, should a particular design be used to …

Spatio-Temporal Soil Moisture Measurement With Wireless Underground Sensor Networks, Xin Dong, Mehmet C. Vuran

School of Computing: Conference and Workshop Papers

In this paper, the estimation distortion of distributed soil moisture measurement using Wireless Underground Sensor Networks (WUSNs) is investigated. The main focus of this paper is to analyze the impact of the environment and network parameters on the estimation distortion of the soil moisture.More specifically, the effects of rainfall, soil porosity, and vegetation root zone are investigated by exploiting a rainfall model, in addition to the effects of sampling rate, network topology, and measurement signal noise ratio. Spatio-temporal correlation is characterized to develop a measurement distortion model with respect to these factors. The evaluations reveal that with porous soil and …

Cost Efficiency Of Anycast-Based Forwarding In Duty-Cycled Wsns With Lossy Channel, Yuyan Xue, Mehmet C. Vuran, Byrav Ramamurthy

School of Computing: Conference and Workshop Papers

Anycasting has been proposed recently as an efficient communication method for asynchronous duty-cycled wireless sensor networks. However, the interdependencies between end-toend communication cost and the anycasting design parameters have not been systematically studied. In this paper, a statistical endtoend cost model is presented to capture the end-to-end latency and energy consumption of anycasting operation under a realistic wireless channel model. By exploring the relationship between the end-to-end cost efficiency and the forwarding decision dependent anycasting design parameters, two anycasting forwarding metrics are proposed for fully distributed forwarding decision. By exploring the relationship among the preamble length, the size of the …

Stochastic Analysis Of Energy Consumption In Wireless Sensor Networks, Yunbo Wang, Mehmet C. Vuran, Steve Goddard

School of Computing: Conference and Workshop Papers

Limited energy resources in increasingly sophisticated wireless sensor networks (WSNs) call for a comprehensive crosslayer analysis of energy consumption in a multi-hop network. For reliability analysis in such networks, the statistical information about energy consumption and lifetime is required. However, traditional energy analysis approaches only focus on the average energy consumed. In this paper, instead, we provide a stochastic analysis of the energy consumption in a random network environment. Accordingly, a comprehensive cross-layer analysis framework, which employs a stochastic queueing model, is developed. Using this framework, the distribution of energy consumption for nodes in WSNs during a given time period …

A First Practical Algorithm For High Levels Of Relational Consistency, Shant Karakashian, Robert J. Woodward, Christopher Reeson, Berthe Y. Choueiry, Christian Bessiere

School of Computing: Conference and Workshop Papers

Consistency properties and algorithms for achieving them are at the heart of the success of Constraint Programming. In this paper, we study the relational consistency property R(*,m)C, which is equivalent to m-wise consistency proposed in relational databases. We also define wR(*,m)C, a weaker variant of this property. We propose an algorithm for enforcing these properties on a Constraint Satisfaction Problem by tightening the existing relations and without introducing new ones. We empirically show that wR(*,m)C solves in a backtrackfree manner all the instances of some CSP benchmark classes, thus hinting at the tractability …