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The Sloan Sag: A Mid-Miocene Volcanotectonic Depression, North-Central Mccullough Mountains, Southern Nevada, Hayden L. Bridwell

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the Hidden Valley area of the north-central McCullough Mountains, southern Nevada, mid-Miocene andesite and dacite domes, flows and pyroclastic units (the Sloan volcanics) partially fill a sag in the underlying Hidden Valley volcanics. The 13.5 km diameter sag formed during and/or after the eruption of the Sloan volcanics. Sagging was accommodated by a combination of movement on the McCullough Wash fault system, and subsidence into evacuated chambers.

Major, trace and rare-earth element geochemistry suggests that the rocks of the Sloan volcanics belong to four groups, each of which were produced by partial melting of chemically distinct sources. With the …

Electron-Energy And –Angular Distributions In The Double Photoionization Of Helium, R. Wehlitz, Franz Heiser, Oliver Hemmers, B. Langer, A. Menzel, U. Becker

Environmental Studies Faculty Publications

Photoelectron spectra of helium have been measured at different angles and at various energies above the double-ionization threshold up to 120 eV to investigate the behavior of the energy and angular distributions, of shake-off electrons. Both energy and angular distributions clearly show a U-shaped profile which turns to a flat curve near threshold pointing to a uniform intensity distribution over the kinetic energy for all angles in this excitation energy regime. Our results for the angular-distribution asymmetry parameter indicate qualitative agreement with theoretical predictions but fail to provide them quantitatively.

Measurement Of The Ratio Of Double-To-Single Photoionization Of Helium At 2.8 Kev Using Synchrotron Radiation, Jon C. Levin, Dennis W. Lindle, N. Keller, R. D. Miller, Y. Azuma, N. Berrah Mansour, H. G. Berry, Ivan A. Sellin

Chemistry and Biochemistry Faculty Research

We report the first measurement of the ratio of double-to-single photoionization of helium well above the double-ionization threshold. Using a time-of-flight technique, we find He⁺⁺/He⁺=1.6±0.3% at hν=2.8 keV. This value lies between calculations by Amusia (2.3%) and by Samson, who predicts 1.2% by analogy with electron-impact ionization cross sections of singly charged ions. Good agreement is obtained with older shake calculations of Byron and Joachain, and of Åberg, who predict 1.7%.

Anisotropy Of Polarized X-Ray Emission From Molecules, S. H. Southworth, Dennis W. Lindle, R. Mayer, P. L. Cowan

Chemistry and Biochemistry Faculty Research

Strongly anisotropic, polarized Cl K-V x-ray emission from gas-phase CF₃Cl has been observed following resonant excitation with a linearly polarized x-ray beam. Distinctively different angular distributions are observed for x-ray emission involving molecular orbitals of different symmetries. A classical model of the x-ray absorption-emission process accurately describes the observed radiation patterns.

Molecular-Orbital Studies Via Satellite-Free X-Ray Fluorescence: Cl-K Absorption And K–Valence-Level Emission Spectra Of Chlorofluoromethanes, Rupert C. Perera, P. L. Cowan, Dennis W. Lindle, R. E. Lavilla, T. Jach, R. D. Deslattes

Chemistry and Biochemistry Faculty Research

X-ray absorption and emission measurements in the vicinity of the chlorine K edge of the three chlorofluoromethanes have been made using monochromatic synchrotron radiation as the source of excitation. By selectively tuning the incident radiation to just above the Cl 1s single-electron ionization threshold for each molecule, less complex x-ray-emission spectra are obtained. This reduction in complexity is attributed to the elimination of multielectron transitions in the Cl K shell, which commonly produce satellite features in x-ray emission. The resulting "satellite-free" x-ray-emission spectra exhibit peaks due only to electrons in valence molecular orbitals filling a single Cl 1s vacancy. These …

Polarized X-Ray-Emission Studies Of Methyl Chloride And The Chlorofluoromethanes, Dennis W. Lindle, P. L. Cowan, T. Jach, R. E. Lavilla, R. D. Deslattes, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

A new technique sensitive to molecular orientation and geometry, and based on measuring the polarization of x-ray emission, has been applied to the Cl-containing molecules methyl chloride (CH₃Cl) and the chlorofluoromethanes (CF₃Cl, CF₂Cl₂, and CFCl₃) in the gas phase. Upon selective excitation using monochromatic synchrotron radiation in the Cl K-edge (Cl 1s) near-threshold region, polarization-selective x-ray emission studies reveal highly polarized molecular valence x-ray fluorescence for all four molecules. The degree and the orientation of the polarized emission are observed to be sensitive to the incident excitation energy near …

Unlv "Rebels" Vs. University Of California, Santa Barbara And Unlv "Rebels" Vs. New Mexico State, University Of Nevada, Las Vegas

UNLV Basketball Programs

Team roster for all schools.

UNLV Schedule

List of UNLV Scholarship Donors

Meet the Rebels

Opponent's Scouting Report

Jerry Tarkanian Story

Also contains information on other sports at UNLV

High-Resolution Photoelectron Spectrometry Study Of Conjugate Shakeup Processes In The Li 1s Threshold Region, B. Langer, J. Viefhaus, Oliver Hemmers, A. Menzel, U. Becker

Environmental Studies Faculty Publications

Partial cross sections and angular-distribution asymmetry parameters of diagram and satellite lines associated with Li 1s photoionization were measured using synchrotron-radiation excitation. Special emphasis was given to a high-resolution study of the ¹P and ³P conjugate shakeup satellite lines testing qualitative predictions of the conjugate shakeup model: increasing σ and decreasing β values towards threshold, both being verified. Comparison with recent relaxed Hartree-Fock calculations shows good agreement for the ¹P satellite, but demonstrates also that the present theory does not seem to be able to describe the cross-section behavior of the ³P satellite correctly.

A Methodological Study And Forecasting Of Room Occupancy Trend In Las Vegas, William Weixia Wang

UNLV Retrospective Theses & Dissertations

The purpose of this research is to develop a systematic methodology for occupancy forecasting and to obtain the future occupancy trend for the Las Vegas hotel/motel industry; A systematic analytical model is developed for generic hotel/motel occupancy forecasting; The analytical model includes log-linear regression models and "other" extrapolation forecasting models for model parameter estimation and optimization; The model is applied to Las Vegas and the U.S. lodging occupancy data from 1973 through 1990 and is used to forecast Las Vegas and the U.S. room occupancies from 1991 through 1993.

Determinants Of The Structural Niches Of Columnar Cacti In The Southwest, Joseph George Hentz

UNLV Retrospective Theses & Dissertations

I evaluated whether morphological differences among populations of Carnegiea gigantea and Pachycereus pringlei actually represent evolutionary adaptation, different developmental responses to the environment, or simply differences in population age structure. Populations of Carnegiea running east to west across southern Arizona differ primarily in size structure, not in growth form. Where growth form differences do exist, they are correlated with variation in aridity. Carnegiea and Pachycereus in less xeric environments have more branches, greater total branch length, and earlier initiation of branching than those of equal height in more xeric environments. I found no evidence of evolutionary divergence among Carnegiea or …

Direct Determination Of Molecular-Orbital Symmetry Of H2s Using Polarized X-Ray Emission, R. Mayer, Dennis W. Lindle, S. H. Southworth, P. L. Cowan

Chemistry and Biochemistry Faculty Research

X-ray emission from the molecule H₂S is strongly polarized following excitation of a sulfur K-shell electron to an unoccupied subthreshold molecular orbital with a polarized x-ray beam. Changes in the polarization of the emission spectrum are observed as the incident beam's energy is swept across the subthreshold absorption resonance. The previously unresolved absorption resonance is shown experimentally to be primarily associated with a molecular orbital of b₂ symmetry, but with a high-excitation-energy component due to an orbital with a₁ symmetry. Satellite emission intensity is shown to depend on the primary photon energy and is therefore associated …

An Investigation Of Photon Correlation Spectroscopy Data Analysis Packages "Discrete" And "Contin" Using The Schulz-Zimm Distribution, Usman Abdul Aziz Qazi

UNLV Retrospective Theses & Dissertations

DISCRETE and CONTIN are standard data analysis packages used in Photon Correlation Spectroscopy for inversion of noisy autocorrelation functions. Their resolution was studied using simulated autocorrelation data based on the Schulz-Zimm distribution of polymer radii; Autocorrelation functions with various noise levels were fitted to both programs. The CONTIN output was compared with the original distribution. Autocorrelation functions calculated for broader distributions of radii yielded correspondingly broader functions in the radius space. Features like the skewness of the original Schulz-Zimm distribution were not recovered except in the case of narrow, approximately monodisperse radius distributions. Addition of noise was not found to …

Formulation Of A Full Dynamic Transport Model For Heterojunction Devices, Anoushiravan Arman

UNLV Retrospective Theses & Dissertations

In this thesis a Full Dynamic Transport Model is presented which consists of the Momentum Conservation Equation (MCE), Energy Conservation Equation (ECE), Particle Conservation Equation (PCE), and Poisson's Equation. In our model carrier velocity and electron energy are taken as variables and have been found using electron concentration and electrostatic potential; It has been found that by increasing the doping from 10{dollar}\sp{16}cm\sp{-3}{dollar} to 5 {dollar}\times{dollar} 10{dollar}\sp{17}cm\sp{-3}{dollar}, the built-in voltage of an {dollar}Al\sb{0.3}Ga\sb{0.7}As/GaAs{dollar} heterojunction increases from 1.33V to 1.54V which is consistent with the results reported by others (1) {dollar}-{dollar} (4). Maximum velocity of electrons changes from 2.5 {dollar}\times{dollar} 10{dollar}\sp7{dollar}cm/sec to …

Feedback Linearization, Invertibility Of Map, Zero Dynamics, And Nonlinear Control Of The Space Station, Theodore Charles Bossart

UNLV Retrospective Theses & Dissertations

Based on feedback linearization and ultimate boundedness theory, a new approach to attitude control of the space station using control moment gyros (CMG's) is presented. A linearizing transformation is derived to obtain a simple linear representation of the nonlinear pitch axis dynamics. A feedback control law for trajectory tracking is derived when there is no disturbance torque acting on the space station. For attitude control in the presence of uncertain torque input, an additional control signal is superimposed such that in the closed-loop system, attitude responses are uniformly ultimately bounded and tend to a small set of ultimate boundedness. Extension …

Early Speculative Bubbles And Increases In The Supply Of Money, Douglas Edward French

UNLV Retrospective Theses & Dissertations

This paper examines three episodes in economic history that are commonly referred to as "speculative bubbles." The three bubbles analyzed are: Tulipmania, the Mississippi Bubble and the South Sea Bubble. The paper views these three events in a historical context emphasizing the monetary interventions particular to each episode; The Rational Expectations and Keynesian school's treatments of speculative bubbles are considered and rejected. The life and monetary theories of John Law are examined extensively, given his influence over the Mississippi and South Sea bubbles. Law is also indirectly connected to the Tulipmania, having been influenced by the operation of the Bank …

Inverse And Variable Structure Trajectory Control Of A Flexible Robotic Manipulator, Sethu K Madhavan

UNLV Retrospective Theses & Dissertations

This thesis introduces two schemes that control the end effector trajectory and stabilize a two-link flexible robotic arm. They are (i) The Inverse Trajectory Control scheme and (ii) The Variable Structure System (VSS) scheme; The Inverse Trajectory Control scheme develops a control law based on the inversion of an input-output map. The stable maneuver of the arm depends on the stability of the zero dynamics of the system. A linear stabilizer is designed for the final capture of the terminal state and stabilization of the elastic modes; The second scheme incorporates a Variable Structure Control law which includes robustness in …

The Effects Of Mathematics Methods Courses On The Mathematical Attitudes, Content Knowledge, And Pedagogical Beliefs Of Preservice Teachers, Robert John Quinn

UNLV Retrospective Theses & Dissertations

This study investigated the effects of mathematics methods courses on the mathematical attitudes, content knowledge, and pedagogical beliefs of preservice elementary teachers and preservice secondary mathematics teachers. The study was conducted during the fall semester of 1992 at the University of Nevada, Las Vegas. Forty-seven preservice teachers participated voluntarily. Twenty-eight were enrolled in an elementary mathematics methods course; nineteen were enrolled in a secondary mathematics methods course; Attitudes toward mathematics were studied quantitatively by administering Aiken's Revised Attitude Scale on a pretest-posttest basis. The results indicated that the attitude toward mathematics of preservice elementary teachers improved significantly. The attitude toward …

Inversion Of Input/Output Map, Sliding Mode And Nonlinear Flight Control System Design, James J. Romano

UNLV Retrospective Theses & Dissertations

We present the review of two approaches for control system design. These are: (i) Non-Linear Inverse Dynamics and (ii) Variable Structure Control; These two schemes of design are applied to a realistic aircraft flight model. The equations of motion are highly nonlinear and the design of a control system for large roll-coupled maneuvers is not a simple task. Analytical derivations of control laws are presented in this thesis for the maneuver of the aircraft using inversion and variable structure control techniques. A short theoretical treatment of each technique is developed and their applications to flight control design are presented; Several …

Gas Chromatography/Fourier Transform Infrared Spectroscopy/Mass Spectrometry For Environmental Analysis: A Quick Turnaround Method For The Analysis Of Polycyclic Aromatic Hydrocarbons, Irene Marie Farnham

UNLV Retrospective Theses & Dissertations

Two methods for organic analysis of environmental samples are discussed. The quantitative capabilities of a gas chromatograph/Fourier transform infrared spectrometer/mass spectrometer were investigated. Three methods of quantitation using FT-IR were examined. These methods were: the Gram-Schmidt method, maximum absorbance method and the integrated absorbance method. The results were compared to those obtained from the mass spectrometer operating in the single and total ion mode. The effect that injection volume has on quantitation was also investigated. Injection volumes of up to 100 uL were introduced to the GC/FT-IR/MS system using a large retention gap which preceded the analytical column; This report …

Modeling Of The Unlv-Aro Light-Weight Robot Using Lagrange's Assumed Mode Method, Symbolic Manipulation, And Numerical Simulation, Edward Yuk-Kam Lam

UNLV Retrospective Theses & Dissertations

This thesis modeled the dynamics of the UNLV-ARO serially connected light-weight robot. The two outer-most links of the robot exhibited flexible behavior in the in-plane and the out-of-plane directions. Lagrangian mechanics were used to model this system. Assumed modes method was used to approximate the vibration mode shape of the links. Using these analytical techniques in conjunction with the inverse dynamics method, a set of equations of motion was formulated to describe the vibrations of the robot. Due to the complexity of the system, the equations of motion were derived using MACSYMA, a symbolic software. From MACSYMA, the equations of …

Output Feedback Rotational Maneuvers And Vibration Damping Of Nasa Scole System By Inversion Theory, Misbahul Azam

UNLV Retrospective Theses & Dissertations

We treat the question of large rotational maneuver and vibration stabilization of NASA Spacecraft Control Laboratory Experiment System (SCOLE). The mathematical model of SCOLE System includes the dynamical equations for rigid body slew maneuver and three dimensional vibration of the rigid space shuttle, the flexible beam and the reflector with an offset mass. The contribution of this thesis lies in the development of two control systems based on (i) Euler angles or (ii) angular velocity components as output variables for large rotational maneuvers and vibration suppression of the SCOLE System. Nonlinear inversion theory is used for the design. The design …

Littoral And Limnetic Zooplankton Communities In Lake Mead, Nevada-Arizona, Usa, Patrick J. Sollberger, Larry J. Paulson

Publications (WR)

Zooplankton were collected from adjacent littoral and limnetic sites in Lake Mead, Nevada-Arizona, USA. Limnetic species dominated both littoral and limnetic zooplankton communities; littoral species rarely exceeded 2% of monthly total zooplankton densities. Low species richness of littoral taxa and high similarity in species composition between littoral and limnetic habitats appeared to result from uniform horizontal physical and chemical environments, due to horizontal mixing, and from the absence aquatic macrophytes. Significant differences in spatial distribution occurred in phytoplankton biomass, total zooplankton density, and fish "abundances; highest concentrations of these factors occurred nearest an inflow high in nutrients and progressively declined …

Hydrogeology And Hydrogeochemistry Of The Shallow Alluvial Aquifer Zone, Las Vegas Valley, Nevada, Harry Stephen Wild Jr.

UNLV Theses, Dissertations, Professional Papers, and Capstones

In Las Vegas Valley, Nevada, the shallow alluvial aquifer zone is a possible source of contamination to the principal alluvial aquifers that provide 30% of the public drinking water supply for the valley. Development of the principal aquifers has lowered pressure head in the principal aquifers and created the potential for downward seepage from the shallow aquifer zone. This study was undertaken to characterize the hydrogeology and hydrogeochemistry of the shallow alluvial aquifer zone and to compare the hydrogeochemistry of the shallow and principal alluvial aquifer zones.

A 37 well shallow ground water monitoring network was established and water-level, water-quality, …

Lake Mead Nutrient Enhancement Project, Peter D. Vaux, Larry J. Paulson, Nevada Department Of Wildlife, National Oceanic And Atmospheric Administration

Publications (WR)

The Lake Mead Fertilization Project is a research program designed to investigate the potential for using large-scale artificial fertilization to enhance the game fisheries of this reservoir through an increase in the population of threadfin shad, the system's primary forage species. A substantial decline in the population of largemouth bass, together with poor condition of adult striped bass, are the two major issues affecting the Lake Mead game fisheries. Both issues have been hypothesized to be a result of an inadequate amount of forage in the reservoir. Previous studies have in turn suggested that a major factor limiting the shad …

Argon-Photoion–Auger-Electron Coincidence Measurements Following K-Shell Excitation By Synchrotron Radiation, Jon C. Levin, C. Biedermann, N. Keller, L. Liljeby, C.-S. O, R. T. Short, Ivan A. Sellin, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Argon photoion spectra have been obtained for the first time in coincidence with K-LL and K-LM Auger electrons, as a function of photon energy. The simplified charge distributions which result exhibit a much more pronounced photon-energy dependence than do the more complicated noncoincident spectra. In the near-K-threshold region, Rydberg shakeoff of np levels, populated by resonant excitation of K electrons, occurs with significant probability, as do double-Auger processes and recapture of the K photoelectron through postcollision interaction.

Enhancement And Monitoring Of The Procambarus Clarkii Population In Lake Mead, Mikell Beth Hager

Publications (WR)

Procambarus clarkii are found in extremely low numbers throughout Lake Mead, AZ-NV. The crayfish are an important dietary component for game fish. Enhancement of the crayfish population would broaden the fishery forage base. Crayfish were stocked and monitored in a study cove on Saddle Island to determine if the Procambarus clarkii population could be enhanced. A trapping survey of the area after the following reproductive season yielded low numbers of crayfish. A comparison of pre-stocking and post-stocking catch per trap day (CPTD) values revealed no significant increase in the population. Procambarus clarkii growth is limited by environmental factors in Lake …

Stromatolites Of The Lower Cambrian Deep Spring Formation; Mount Dunfee, Esmeralda County, Nevada, Lynn Oliver

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Middle Member of the Lower Cambrian Deep Spring Formation at Mount Dunfee, Nevada contains a diverse assemblage of stromatolites that formed on a tide- and storm-dominated, siliciclastic-influenced, carbonate shelf. The stromatolites formed in a shallow subtidal environment within and near active oolite shoals under strongly focused currents. The stromatolites occur in four different lithofacies: (1) bioherms of digitate stromatolites, (2) bioherms and biostromes of inclined stromatolites, (3) isolated forms of massive and hemispheroidal stromatolites, and (4) a biostrome of cryptomicrobial boundstones. The first three lithofacies are interpreted as microbial reefs. They had topographic relief, formed in active agitated waters, …

Critical Thinking In Education: What Can The Matter Be?, Gail K Lenning

UNLV Retrospective Theses & Dissertations

The paper presents expert commentary on this issue, where informal logic and philosophy are found to be the favored approaches to the teaching of critical thinking, followed by the interpretation and evaluation of the two major types of programs used to teach critical thinking skills; Lipman's Philosophy for Children program is explained as a specific class intended to teach children to reason by means of a dialogical, philosophical approach; Thoughtful teaching or the across-the-curriculum approach will be explained as to its basic parts, which are a selection of skills and a teaching method to introduce them. There is no universally …

System Identification Of A Hydraulically-Actuated Robot, Andreas Otto Ranz

UNLV Retrospective Theses & Dissertations

A feedback control system has been developed to operate an elastic robot arm. This work was funded by a grant from the U.S. Army Research Office. The goal of this investigation was to experimentally determine the operating curves, performance plots, and flow coefficients needed to produce an appropriate servovalve signal when operating the hydraulically-actuated robot arm. Through the assimilation of data collected in the laboratory the parameters were determined.

Adaptive Control Of Decouplable Systems And Nonlinear Flight Control Systems, Sahjendra N. Singh, William R. Wells

Electrical & Computer Engineering Faculty Research

This paper treats the question of output trajectory tracking in nonlinear systems in the presence of uncertainty. It is assumed that the nominal system is decouplable using state variable feedback. An adaptive control law is derived such that in the closed-loop system, output vector asymptotically converges to the given reference trajectory. The controller includes a dynamic system in the feedback path. This result is applied to design a flight control system to control roll angle, angle of attack and sideslip in rapid, nonlinear maneuvers of aircraft.