Physical Sciences and Mathematics Commons^™

Spectroscopic Investigation Of Palladium-Copper Bimetallic Systems For Pem Fuel Cell Catalysts, Timo Hofmann

UNLV Theses, Dissertations, Professional Papers, and Capstones

One of the main barriers to commercialization of polymer electrolyte membrane fuel cells systems is cost, which is largely due to the need of platinum (Pt)-containing catalysts. In this thesis we investigate bimetallic systems consisting of a base metal (copper) and a noble metal (palladium) that, as an alloy on the nanoscale, mimic the electronic properties that make Pt desirable as a catalyst.

We present a detailed investigation of the electronic structure of carbon-supported Pd/Cu nanoparticle catalysts, model bilayer thin film systems, alloys, and various metal reference samples. We have investigated the valence band structure of the catalysts using a …

An Evaluation Of Lead Hazards In Pre-1978 Residental Housing Within Clark County, Nevada, Usa, Erika Raquel Torres

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lead poisoning remains a public health concern due to leads persistence in the environment from anthropogenic uses. Initial efforts to address the impacts of lead on vulnerable communities have included secondary prevention measures which typically occur after a child has been poisoned. However, in recent years there has been a pragmatic shift toward primary prevention efforts.

This study evaluates lead hazards identified through primary prevention activities in residential housing within Clark County, Nevada, USA. It is the first study to systematically address and evaluate pre-1978 housing in Southern Nevada. Risk assessments were conducted in 81 dwellings built prior to 1979 …

Examining The Influence Of Restaurant Green Practices On Customer Return Intention, Audrey L. Szuchnicki

UNLV Theses, Dissertations, Professional Papers, and Capstones

In recent years there has been an increased awareness of how the actions of the foodservice industry are effecting the environment. With this awareness we have begun to see a change in priorities for both new and existing businesses. At the forefront of this change in the "green" direction is the GRA who certifies how eco-friendly an establishment is based on its' environmental guidelines. This study will examine the correlation between customer return intention and the institution of green practices within a restaurant setting. The expected outcome would be that a restaurant that is certified green or, implementing measures to …

Empirically Derived Formulas To Predict Indoor Maximum, Average, And Minimum Temperatures In Roofpond Buildings Using Minimum Climatic Information, Ibrahim Kivarkis Kako

UNLV Theses, Dissertations, Professional Papers, and Capstones

This thesis introduces an empirically developed formula to predict the comfort conditions and thermal performance of a Skytherm(TM) Southwest Roofpond placed over a light-weight un-insulated structure built at the School of Architecture at the University of Nevada, Las Vegas.

The predictive formula introduced in this study may be used in different parts of the world (particularly developing nations where insulation and air-conditioning are rarely used) to predict the performance of a Skytherm(TM) Southwest Roofpond using minimal climate data.

The data collected in the experimental setup at the Natural Energies Advanced Technologies Laboratory included outside and inside temperatures of various surfaces …

Fate Of Sulfamethoxazole, 4-Nonylphenol, And 17Β-Estradiol In Groundwater Contaminated By Wastewater Treatment Plant Effluent, Larry Barber, Steffanie Keefe, Dennis Leblanc, Paul Bradley, Francis Chapelle, Michael Meyer, Keith Lofton, Dana Kolpin, Fernando Rubio

United States Geological Survey: Staff Publications

Organic wastewater contaminants (OWCs) were measured in samples collected from monitoring wells located along a 4.5- km transect of a plume of groundwater contaminated by 60 years of continuous rapid infiltration disposal of wastewater treatment plant effluent. Fifteen percent of the 212OWCs analyzed were detected, including the antibiotic sulfamethoxazole (SX), the nonionic surfactant degradation product 4-nonylphenol (NP), the solvent tetrachloroethene (PCE), and the disinfectant 1,4-dichlorobenzene (DCB). Comparison of the 2005 sampling results to data collected from the same wells in 1985 indicates that PCE and DCB are transported more rapidly in the aquifer than NP, consistent with predictions based on …

Biodegradation Of 17Β-Estradiol, Estrone And Testosterone In Stream Sediments, Paul Bradley, Larry Barber, Francis Chapelle, James Gray, Dana Kolpin, Peter B. Mcmahon

United States Geological Survey: Staff Publications

Biodegradation of 17β-estradiol (E2), estrone (E1), and testosterone (T) was investigated in three wastewater treatment plant (WWTP) affected streams in the United States. Relative differences in the mineralization of [4-¹⁴C] substrates were assessed in oxic microcosms containing saturated sediment or water-only from locations upstream and downstream of the WWTP outfall in each system. Upstream sediment demonstrated significant mineralization of the “A” ring of E2, E1, and T, with biodegradation of T consistently greater than that of E2 and no systematic difference in E2 and E1 biodegradation. “A” ring mineralization also was observed in downstream sediment, with E1 and …

Response Of Sandhill Crane (Grus Canadensis Riverine Roosting Habitat To Changes In Stage And Sandbar Morphology, Paul Kinzel, Jonathan Nelson, Ashley Heckman

United States Geological Survey: Staff Publications

Over the past century, flow regulation and vegetation encroachment have reduced active channel widths along the central Platte River, Nebraska. During the last two decades, an annual program of in-channel vegetation management has been implemented to stabilize or expand active channel widths. Vegetation management practices are intended to enhance riverine habitats which include nocturnal roosting habitat for sandhill cranes. Evaluating the success of other management treatments such as streamflow modification requires an understanding of how flow shapes the sandbars in the river and how sandbar morphology interacts with flow to create crane habitat. These linkages were investigated along a 1-km …

Ultrashort Pulse Electron Gun With A Mhz Repetition Rate, D. Wytrykus, Martin Centurion, P. Reckenthaeler, F. Krausz, A. Apolonski, E. Fill

Martin Centurion Publications

We report the construction of an electron gun emitting ultrashort pulses with a repetition rate of 2.7 MHz. The gun works at an acceleration voltage of 20 kV and is operated with a laser oscillator having an ultralong cavity. A low number of electrons per pulse eliminates space charge broadening. Electron yield and beam profiles are measured for operation with laser wavelengths of 800, 400, and 266 nm. The initial energy spread of the electrons is determined for these three wavelengths, and pulse durations of 600, 390, and 270 fs are inferred from the data.

Complex Magnetic Phase In Submonolayer Fe Stripes On Pt(997), Jan Honolka, T. Y. Lee, K. Kuhnke, D. Repetto, V. Sessi, Peter Wahl, A. Buchsbaum, P. Varga, S. Gardonio, C. Carbone, S. R. Krishnakumar, P. Gambardella, M. Komelj, R. Singer, M. Fähnle, K. Fauth, G. Schütz, Axel Enders, K. Kern

Axel Enders Publications

Correlations between magnetism and morphology of iron nanostructures of monatomic height on Pt(997) substrates are studied using x-ray magnetic circular dichroism as well as scanning tunneling microscopy and helium scattering. A drastic collapse of the average magnetization by more than a factor of 4 is observed when increasing the iron coverage from 0.1 to 0.2 ML. This effect goes along with a softening of the magnetic anisotropy energy and a gradual reorientation of the magnetic easy axis from in plane to out of plane. The experimental findings together with electronic density-functional calculations suggest the formation of a complex magnetic phase …

Self-Assembly Of Magnetic Ni Nanoparticles Into 1d Arrays With Antiferromagnetic Order, Valery Bliznyuk, Srikanth Singamaneni, Sarbeswar Sahoo, Srinivas Polisetty, Xi He, Christian Binek

Christian Binek Publications

In this paper, we report on the magnetic properties of isolated nanoparticles and interacting nanochains formed by the self-assembly of Ni nanoparticles. The magnetic properties were studied using superconducting quantum interference device (SQUID) magnetometry and magnetic force microscopy (MFM). We demonstrate that single-domain Ni nanoparticles spontaneously form one-dimensional (1D) chains under the influence of an external magnetic field. Furthermore, such magnetic field-driven self-assembly in conjunction with surface templating produces regular arrays of 1D nanochains with antiferromagnetic intra-chain order. The antiferromagnetic order, which is in striking contrast to what is found for non-interacting nanoparticle assemblies within the chains, can be evidenced …

Magnetism Of Cr-Doped Diamond-Like Carbon, J. A. Colón Santana, Ralph Skomski, V. R. Singh, V. Palshin, A. Petukhov, Yaroslav B. Losovyj, Andrei Sokolov, Peter A. Dowben, Ihor Ketsman

Peter Dowben Publications

Chromium-doped hydrogenated diamond-like carbon (Cr-DLC) and chromium carbide hydrogenated DLC alloys were synthesized by plasma-assisted vapor deposition and investigated by x-ray absorption near edge structure spectroscopy, extended x-ray absorption fine structure, and superconducting quantum interference device (SQUID) magnetometry. Structural and magnetic properties of the doped and alloy materials were investigated as a function of the Cr concentration (0.1–20 at. %). Toward the upper end of the concentration range, Cr precipitates in the form of chromium carbide (Cr₃C₂) nanoclusters. For low Cr concentrations, the systems are ferromagnetic at very low temperatures, whereas the chromium carbide clusters appear …

Radiation-Induced Decomposition Of The Metal-Organic Molecule Bis(4-Cyano-2,2,6,6-Tetramethyl-3,5-Heptanedionato)Copper(Ii), David Wisbey, Ning Wu, Yaroslav B. Losovyj, Ihor Ketsman, A. N. Caruso, Danqin Feng, John Belot, Elio Vescovo, Peter A. Dowben

Peter Dowben Publications

The effects of vacuum ultraviolet radiation on the adsorbed copper center molecule bis(4-cyano-2,2,6,6- tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)₂), (C₂₄H₃₆N₂O₄Cu, Cu(II)) was studied by photoemission spectroscopy. Changes in the ultraviolet photoemission spectra (UPS) of Cu(CNdpm)₂, adsorbed on Co(1 1 1), indicate that the ultraviolet radiation leads to decomposition of Cu(CNdpm)₂ and this decomposition is initially dominated by loss of peripheral hydrogen.

The Surface Core Level Shift For Lithium At The Surface Of Lithium Borate, David Wooten, Ihor Ketsman, Jie Xiao, Yaroslav B. Losovyj, J. C. Petrosky, J. Mcclory, Ya. V. Burak, V. T. Adamiv, Peter A. Dowben

Peter Dowben Publications

The shallow Li 1s core level exhibits a surface-to-bulk core level shift for the stoichiometric Li₂B₄O₇ (1 1 0) surface. Angle-resolved photoemission spectroscopy was used to identify Li1s bulk and surface core level components at binding energies –56.5 ± 0.4 and –53.7 ± 0.5 eV, respectively. We find photoemission evidence for surface states of Li₂B₄O₇ (1 1 0) that exist in the gap of the projected bulk density of states. The existence of surface states is consistent with the large surface-to-bulk core level shift for the Li 1s core.

Induced Spin Polarization Of Copper Spin 1/2 Molecular Layers, David Wisbey, Ning Wu, Danqin Feng, A. N. Caruso, J. Belot, Yaroslav B. Losovyj, Elio Vescovo, Peter A. Dowben

Peter Dowben Publications

Thin films of the metal organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)₂), (C₂₄H₃₆N₂O₄Cu, Cu(II)), deposited on ferromagnetic Co(111) at 40 K, exhibit a finite electron spin polarization. The spin polarization magnitude and sign for Cu(CNdpm)₂ deposited on Co(111) is coverage dependent, but deviates from the mean field expectations for a simple paramagnet on a ferromagnetic substrate. The spin asymmetry is seen to favor select molecular orbitals, consistent with the predicted single molecule density of states. The overlayer polarization observed indicates a strong influence of the ferromagnetic Co(111) substrate and some extra-molecular …

Search For The Lightest Scalar Top Quark In Events With Two Leptons In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We report results of a search for the pair production of the lightest supersymmetric partner of the top quark, t₁, using a data set corresponding to an integrated luminosity of 1 fb⁻¹ collected by the DØ detector at a pp center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. Both scalar top quarks are assumed to decay into a b quark, a charged lepton and a scalar neutrino. The search is performed in the electron plus muon and dielectron final states. The signal topology consists of two isolated leptons, missing transverse energy, and jets. We find …

Relative Rates Of B Meson Decays Into Ψ(2S) And J/Ψ Mesons, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We report on a study of the relative rates of B meson decays into ψ(2S) and J/ψ mesons using 1.3 fb^-1 of pp collisions at √s = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We observe the channels B⁰_s → ψ(2S)φ, B⁰_s → J/ψφ, B^± → ψ(2S)K^±, and B^± → i>J/ψK^± and we measure the relative branching fractions for these channels to be (B(B_s⁰ → ψ(2 …

Determination Of The Strong Coupling Constant From The Inclusive Jet Cross Section In Pp Collisions At √S= 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We determine the strong coupling constant α_s and its energy dependence from the p_T dependence of the inclusive jet cross section in pp collisions at √s= 1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50<p_T < 145 GeV. Using perturbative QCD calculations to order O(α_s³) combined with O(α_s⁴) contributions from threshold corrections, we obtain α_s(M_Z) =0.1161_-0.0048^+0.0041. This is the most precise result obtained at a hadron-hadron collider.

Combination Of Tt Cross Section Measurements And Constraints On The Mass Of The Top Quark And Its Decays Into Charged Higgs Bosons, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We combine measurements of the top quark pair production cross section in pp collisions in the ℓ + jets, ℓℓ, and τℓ final states (where ℓ is an electron or muon) at a center of mass energy of √s = 1.96 TeV in 1 fb^-1 of data collected with the D0 detector. For a top quark mass of 170 GeV/c², we obtain σ_tt = 8.18_-0.87^+0.98 pb in agreement with the theoretical prediction. Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined tt …

Search For Charged Higgs Bosons In Decays Of Top Quarks, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a search for charged Higgs bosons in decays of top quarks, in the mass range 80 < m_H^± < 155 GeV, assuming the subsequent decay H⁺ → τ⁺v_τ (and its charge conjugate). Using 0.9 fb^-1 of lepton + jets data collected with the D0 detector at the Fermilab Tevatron pp collider, operating at a center of mass energy √s = 1.96 TeV, we find no evidence for a H^± signal. Hence we exclude branching ratios B(t → H⁺b) > 0.24 for m_H^± = 80 GeV and B(t → H …

Observation Of Single Top-Quark Production, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We report observation of the electroweak production of single top quarks in pp collisions at √s = 1.96 TeV based on 2.3 fb^-1 of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of σ(pp → tb + X, tqb + X) = 3.94 ± 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10 …

Measurement Of The Ww Production Cross Section With Dilepton Final States In Pp Collisions At √S = 1.96 Tev And Limits On Anomalous Trilinear Gauge Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We provide the most precise measurement of the WW production cross section in pp collisions to date at a center of mass energy of 1.96 TeV, and set limits on the associated trilinear gauge couplings. The WW → ℓνℓ’ν(ℓ,ℓ’ = e, μ) decay channels are analyzed in 1 fb^-1 of data collected by the D0 detector at the Fermilab Tevatron Collider. The measured cross section is σ(pp → WW) = 11.5 ± 2.1 (stat + syst) ± 0.7 (lumi) pb. One- and two-dimensional 95% C.L. limits on trilinear gauge couplings are provided.

Measurement Of The ZΓ → Ννγ Production Cross Section And Limits On Anomalous ZzΓ And ZΓγ Couplings In Pp Collisions At √S= 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present the first observation of the Zγ → ννγ process at the Fermilab Tevatron at 5.1 standard deviations significance, based on 3.6 fb^-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron pp Collider at √s = 1.96 TeV. The measured Zγ production cross section multiplied by the branching fraction of Z → νν is 32 ± 9(stat + syst) ± 2(lumi) fb for the photon E_T > 90 GeV. It is in agreement with the standard model prediction of 39 ± 4 fb. We set limits on anomalous trilinear Zγγ …

Measurement Of The W Boson Mass, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the W boson mass in W → ev decays using 1 fb^-1 of data collected with the D0 detector during Run II of the Fermilab Tevatron collider. With a sample of 499830 W → ev candidate events, we measure M_W = 80.401 ± 0.043 GeV. This is the most precise measurement from a single experiment.

Measurement Of Dijet Angular Distributions At √S = 1.96 Tev And Searches For Quark Compositeness And Extra Spatial Dimensions, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We present the first measurement of dijet angular distributions in pp collisions at √s = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an integrated luminosity of 0:7 fb^-1 collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25 TeV to above 1.1 TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and TeV^-1 scale extra dimensions. For all models considered, we …

Search For The Standard Model Higgs Boson In Tau Final States, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a search for the standard model Higgs boson using hadronically decaying tau leptons, in 1 fb^-1 of data collected with the D0 detector at the Fermilab Tevatron pp collider. We select two final states: τ^± plus missing transverse energy and b jets, and τ⁺τ^- plus jets. These final states are sensitive to a combination of associated W/Z boson plus Higgs boson, vector boson fusion, and gluon-gluon fusion production processes. The observed ratio of the combined limit on the Higgs production cross section at the 95% C.L. to the standard model expectation is 29 …

Search For Next-To-Minimal Supersymmetric Higgs Bosons In The H → Aa → Μμμμ, Μμττ Channels Using Pp Collisions At √S = 1.96 Tev, V.M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We report on a first search for production of the lightest neutral CP-even Higgs boson (h) in the next-to-minimal supersymmetric standard model, where h decays to a pair of neutral pseudoscalar Higgs bosons (a), using 4.2 fb^-1 of data recorded with the D0 detector at Fermilab. The a bosons are required to either both decay to μ⁺μ^- or one to μ⁺μ and the other to τ⁺τ. No significant signal is observed, and we set limits on its production as functions of M_a and M_h.

Panarchy: Discontinuities Reveal Similarities In The Dynamic System Structure Of Ecological And Social Systems, Ahjond S. Garmestani, Craig R. Allen, Lance Gunderson

School of Natural Resources: Faculty Publications

In this paper, we review the empirical evidence of discontinuous distributions in complex systems within the context of panarchy theory and discuss the significance of discontinuities for understanding emergent properties such as resilience. Over specific spatial-temporal scale ranges, complex systems can configure in a variety of regimes, each defined by a characteristic set of self-organized structures and processes. A system may remain within a regime or dramatically shift to another regime. Understanding the drivers of regime shifts has provided critical insight into system structure and resilience. Although analyses of regime shifts have tended to focus on the system level, new …

Enhancing The Perceived Threat Of Vehicle Approach To Deer, Bradley F. Blackwell, Thomas W. Seamans

United States Department of Agriculture Wildlife Services: Staff Publications

In North America and Europe, deer (Cervidae)–vehicle collisions (DVCs) are common and result not only in injury and death to the animals involved, but also human injury and property damage. Given that most DVCs occur during crepuscular periods, we questioned whether the perceived threat to deer posed by vehicle approach could be enhanced. We hypothesized that a vehicle-based lighting system that better complements peak visual capabilities of deer at night relative to standard tungsten-halogen (TH) lighting alone would elicit a greater flight-initiation distance (FID) by free-ranging white-tailed deer (Odocoileus virginianus). Our lighting system comprised 2 TH lamps and …

Regional Assessment On Influence Of Landscape Configuration And Connectivity On Range Size Of White-Tailed Deer, W. David Walter, Kurt C. Vercauteren, Henry Campa Iii, William R. Clark, Justin W. Fischer, Scott E. Hygnstrom, Nancy E. Mathews, Clayton K. Nielsen, Eric M. Schauber, Timothy R. Van Deelen, Scott R. Winterstein

United States Department of Agriculture Wildlife Services: Staff Publications

Variation in the size of home range of white-tailed deer (Odocoileus virginianus) has broad implications for managing populations, agricultural damage, and disease spread and transmission. Size of home range of deer also varies seasonally because plant phenology dictates the vegetation types that are used as foraging or resting sites. Knowledge of the landscape configuration and connectivity that contributes to variation in size of home range of deer for the region is needed to fully understand differences and similarities of deer ecology throughout the Midwest. We developed a research team from four Midwestern states to investigate how size of …

Survival And Cause-Specific Mortality Of Wild Turkeys In Northern Indiana, Lee A. Humberg, Travis L. Devault, Olin E. Rhodes Jr.

United States Department of Agriculture Wildlife Services: Staff Publications

Information regarding survival and cause-specific mortality of eastern wild turkeys (Meleagris gallopavo silvestris) is vital to their management, especially in small or isolated populations. Between January 2003 and August 2005, we used radio telemetry to investigate survival and cause-specific mortality of 87 [44 male (24 adult and 20 juvenile) and 43 female (34 adult and 9 juvenile)] wild turkeys in northern Indiana. We estimated annual and seasonal survival using the Kaplan-Meier product-limit method. Mean male and female annual survival estimates were 0.257 and 0.777, respectively. Annual survival estimates were different between sexes within years, but were homogenous within …