Physical Sciences and Mathematics | Open Access Articles

Nutrient Loading And Eutrophication In The Great Salt Lake, Wayne A. Wurtsbaugh

Watershed Sciences Faculty Publications

No abstract provided.

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Gravity Has A Story To Tell: Lisa And The Search For Low Frequency Gravitational Waves, Shane L. Larson

Colloquia and Seminars

No abstract provided.

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Usu’S Rayleigh-Scatter Lidar, Vincent B. Wickwar

Presentations

No abstract provided.

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One With The Cosmos: A Short Tour Out Your Backdoor, Shane L. Larson

Public Talks

No abstract provided.

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Seasonal Variations Of Semidiurnal Tidalperturbations In Mesopause Region Temperature And Zonal And Meridional Winds Above Fort Collins, Colorado(40.6°N, 105.1°W), Tao Yuan, H. Schmidt, C. Y. She, D. A. Krueger, S. Reising

All Physics Faculty Publications

On the basis of Colorado State University (CSU) Na lidar observations over full diurnal cycles from May 2002 to April 2006, a harmonic analysis was performed to extract semidiurnal perturbations in mesopause region temperature and zonal and meridional winds over Fort Collins, Colorado (40.6°N, 105.1°W). The observed monthly results are in good agreement with MF radar tidal climatology for Urbana, Illinois, and with predictions of the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), sampled at the CSU Na lidar coordinates. The observed semidiurnal tidal period perturbation within the mesopause region is found to be dominated by propagating modes …

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Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffman, John R. Dennison, Clint D. Thomson, Jennifer Albresten

All Physics Faculty Publications

Electron-induced electron yields of high-resistivity high-yield materials - ceramic polycrystalline aluminum oxide and polymer polyimide (Kapton HN) - were made by using a low-fluence pulsed incident electron beam and charge neutralization electron source to minimize charge accumulation. Large changes in the energy-dependent total yield curves and yield decay curves were observed, even for incident electron fluences of < 3 fC/mm². The evolution of the electron yield as charge accumulates in the material is modeled in terms of electron recapture based on an extended Chung-Everhart model of the electron emission spectrum. This model is used to explain the anomalies measured in highly …

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Gravity Wave And Tidal Influences On Equatorial Spread F Based On Observations During The Spread F Experiment (Spreadfex), D. C. Fritts, S. L. Vadas, D. M. Riggin, M. A. Abdu, I. S. Batista, H. Takahashi, A. Medeiros, F. Kamalabadi, H. L. Liu, B. G. Fejer, Michael J. Taylor

All Physics Faculty Publications

The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in …

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Temperature And Electric Field Dependence Of Conduction In Low-Density Polyethylene, John R. Dennison, Jerilyn Brunson

All Physics Faculty Publications

A traditional constant voltage conductivity test method was used to measure how the conductivity of highly insulating low-density polyethylene (LDPE) polymer films depends on applied electric field, repeated and prolonged electric field exposure, and sample temperature. The strength of the applied voltage was varied to determine the electric field dependence. At low electric field, the resistivity was measured from cryogenic temperatures to well above the glass transition temperature. Comparisons were made with a variety of models of the conduction mechanisms common in insulators, including transient polarization and diffusion and steady-state thermally activated hopping conductivity and variable range hopping conductivity, to …

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Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffmann, Jr Dennison, Clint D. Thomson, Jennifer Albretson

Journal Articles

Electron-induced electron yields of high-resistivity, high-yield materials - ceramic polycrystalline aluminum oxide and the polymer polyimide (Kapton HN), - were made by using a low-fluence, pulsed incident electron beam and charge neutralization electron source to minimize charge accumulation. Large changes in energy-dependent total yield curves and yield decay curves were observed, even for incident electron fluences of <3 fC/mm². The evolution of the electron yield as charge accumulates in the material is modeled in terms of electron re-capture based on an extended Chung-Everhart model of the electron emission spectrum. This model is used to explain anomalies measured in highly insulating, …

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Deep Dielectric Charging Of Spacecraft Polymers By Energetic Protons, Nelson W. Green, Jr Dennison

Journal Articles

The majority of research in the field of spacecraft charging concentrates on electron charging effects with little discussion of charging by protons. For spacecraft orbiting in the traditional LEO and GEO environments, this emphasis on electrons is appropriate since energetic electrons are the dominant species. However, for spacecraft in orbits within the inner radiation belts, or for interplanetary and lunar space probes, proton charging effects may also be of concern. To examine bulk spacecraft charging effects in these environments, several typical highly insulating spacecraft polymers were exposed to energetic protons with energies from 1 to 10 MeV to simulate protons …

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Microtextural Constraints On The Interplay Between Fluidrockreactions And Deformation, Alexis K. Ault, Jane Selverstone

Geosciences Faculty Publications

Schists from two mylonitic localities in the footwall of a low-angle normal fault in the eastern Alps record different degrees of embrittlement during exhumation, depending on the extent to which fluid–rock reactions proceeded. At one site, graphitic schists preserve textural evidence for two metamorphic reactions that modified XCO2XCO2 and/or fluid volume: (1) reaction between graphite and aqueous fluid that increased XCO2XCO2 without changing the molar amount of fluid, and (2) replacement of titanite by rutile, calcite, and quartz. The latter reaction involved net consumption of increasingly CO2-rich fluid. Areas where the first reaction proceeded are associated with abundant Mode I …

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Seasonal And Longitudinal Dependence Of Equatorialdisturbance Vertical Plasma Drifts, Bela G. Fejer, J. W. Jensen, S. Y. Su

Bela G. Fejer

[1] We used equatorial measurements from the ROCSAT-1 satellite to determine the seasonal and longitudinal dependent equatorial F region disturbance vertical plasma drifts. Following sudden increases in geomagnetic activity, the prompt penetration vertical drifts are upward during the day and downward at night, and have strong local time dependence at all seasons. The largest prompt penetration drifts near dusk and dawn occur during June solstice. The daytime disturbance dynamo drifts are small at all seasons. They are downward near dusk with largest (smallest) values during equinox (June solstice); the nighttime drifts are upward with the largest magnitudes in the postmidnight …

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Movement Strategies Of Seed Predators As Determinants Of Plant Recruitment Patterns, Lorenzo Mari, Renato Casagrandi, Marino Gatto, Tal Avgar, Ran Nathan

Wildland Resources Faculty Publications

Plant recruitment in nature exhibits several distinctive patterns ranging from hump shaped to monotonically decreasing with distance from the seed source. We investigate the role of post-dispersal seed predation in shaping these patterns, introducing a new mechanistic model that explicitly accounts for the movement strategy used by seed eaters. The model consists of two partial differential equations describing the spatiotemporal dynamics of both seed and predator densities. The movement strategy is deﬁned by how predators move in response to the different cues they can use to search for seeds. These cues may be seed density, seed intake, distance from the …

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On A New Process For Cusp Irregularity Production, Herbert C. Carlson, K. Oksavik, J. Moen

Faculty publications

Two plasma instability mechanisms were thought until 2007 to dominate the formation of plasma irregularities in the F region high latitude and polar ionosphere; the gradient-drift driven instability, and the velocity-shear driven instability. The former mechanism was accepted as accounting for plasma structuring in polar cap patches, the latter for plasma structuring in polar cap sun aligned arcs. Recent work has established the need to replace this view of the past two decades with a new patch plasma structuring process (not a new mechanism), whereby shear-driven instabilities first rapidly structure the entering plasma, after which gradient drift instabilities build on …

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Vignettes From The World Of Gravitational Wave Astrophysics, Shane L. Larson

Colloquia and Seminars

No abstract provided.

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Songs From The Milky Way: Our Galaxy In Low Frequency Gravitational Waves, Shane L. Larson

Colloquia and Seminars

No abstract provided.

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How Movement Properties Affect Prey Encounter Rates Of Ambush Versus Active Predators: A Comment On Scharf Et Al, Tal Avgar, Nir Horvitz, Luba Broitman, Ran Nathan

Wildland Resources Faculty Publications

Using an individual‐based model, Scharf and coworkers showed that ambush predators may encounter prey more frequently than active predators. We show that this surprising result emerges because active predators were oblivious to prey during movement, an assumption that refutes the common conception about active foraging and lessens the key difference between these foraging modes. A revised model confirms that active predators always encounter prey more frequently, unequivocally supporting the authors’ conclusion that the advantage of active predators diminishes as prey moves faster or more directionally. We suggest that movement‐dependent perception quality can determine the relative efficiency of these two foraging …

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Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffmann, John R. Dennison

All Physics Faculty Publications

Electron-induced electron yields of high-resistivity, high-yield materials - ceramic polycrystalline aluminum oxide and the polymer polyimide (Kapton HN), - were made by using a low-fluence, pulsed incident electron beam and charge neutralization electron source to minimize charge accumulation. Large changes in energy-dependent total yield curves and yield decay curves were observed, even for incident electron fluences of

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Starlight In The Night: Discovering The Secret Lives Of Stars, Shane L. Larson

Public Talks

No abstract provided.

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Richfield Field Office Planning Area - Proposed Resource Management And Final Environmental Impact Statement, United States Department Of The Interior, Bureau Of Land Management

Final environmental Impact Statements (UT)

The Proposed RMP was crafted primarily from the Preferred Alternative presented in the DRMP/DEIS (Alternative B) and includes other decisions within the range of alternatives (Alternatives N, A, C, and D) in response to public comments and internal review. The No Action Alternative (Alternative N) reflects current management. The BLM has removed the DRMP/DEIS Alternative B (Preferred Alternative) from the PRMP/FEIS. The other DRMP/DEIS Alternatives (Alternatives N, A, C, and D) and analyses are carried forward in the PRMP/FEIS only for comparative purposes and to correct some mistakes that were identified during the public comment period.

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Moab Field Office Planning Area Proposed Resource Management Plan And Final Environmental Impact Statement, United States Department Of The Interior, Bureau Of Land Management

Final environmental Impact Statements (UT)

This Proposed Resource Management Plan (RMP) and Final Environmental Impact Statement (EIS) describes and analyzes the Proposed Plan and draft alternatives for the planning and management of public lands and resources administered by the Bureau of Land Management (BLM), Moab Field Office. The Moab planning area is located in southeastern Utah and includes approximately 2.5-million acres of land in Grand and San Juan Counties. Within the Moab planning area, the BLM manages approximately 1.8-million acres of BLM-administered public land surface as well as about 29,000 acres of federal mineral estate.

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Dark Side Of The Universe: Dark Matter In The Galaxy And Cosmos, Shane L. Larson

Public Talks

No abstract provided.

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From Quarks To The Cosmos, Shane L. Larson

Colloquia and Seminars

No abstract provided.

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Whispers From The Cosmos: Seeing The Universe In Gravitational Waves, Shane L. Larson

Colloquia and Seminars

No abstract provided.

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Timing And Cause Of Water Level Fluctuations In Kluane Lake, Yukon Territory, Over The Past 5000 Years, Janice Brahney, John J. Clague, Brian Menounos, Thomas W. D. Edwards

Watershed Sciences Faculty Publications

We reconstructed late Holocene fluctuations of Kluane Lake in Yukon Territory from variations in bulk physical properties and carbon and nitrogen elemental and isotopic abundances in nine sediment cores. Fluctuations of Kluane Lake in the past were controlled by changes in climate and glaciers, which affected inflow of Slims and Duke rivers, the two largest sources of water flowing into the lake. Kluane Lake fluctuated within a narrow range, at levels about 25 m below the present datum, from about 5000 to 1300 cal yr BP. Low lake levels during this interval are probably due to southerly drainage of Kluane …

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Rare Measurements Of A Sprite With Halo Event Driven By A Negative Lightning Discharge Over Argentina, Michael J. Taylor, T. Berkey, Pierre-Dominique Pautet, S. A. Cummer, N. Jaugey, J. N. Thomas, N. N. Solorzano, F. Sao Sabbas, R. H. Holzworth, O. Pinto, N. J. Schuch

All Physics Faculty Publications

As part of a collaborative campaign to investigate Transient Luminous Events (TLEs) over South America, coordinated optical, ELF/VLF, and lightning measurements were made of a mesoscale thunderstorm observed on February 22–23, 2006 over northern Argentina that produced 445 TLEs within a 6 hour period. Here, we report comprehensive measurements of one of these events, a sprite with halo that was unambiguously associated with a large negative cloud-to-ground (CG) lightning discharge with an impulsive vertical charge moment change (DMQv) of 03 C.km. This event was similar in its location, morphology and duration to other positive TLEs observed from this storm. However, …

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Core-Level Spectroscopy Of The Ni/W(110) Interface: Correlation Of W Interfacial Core Levelshifts With First-Layer Ni Phases, D. Mark Riffe, R. T. Franckowiak, N. D. Shinn, B. Kim, K. J. Kim, T. H. Kang

All Physics Faculty Publications

We have measured W 4f_7/2 core-level photoemission spectra from W(1 1 0) in the presence of Ni overlayers, from ∼0.2 to ∼3 monolayers. Interfacial core-level shifts associated with first-layer Ni phases have been identified: −230 ± 15 meV for the 1 × 1 pseudomorphic phase and −70 ± 7 meV for the 7 × 1 close-packed commensurate phase. At higher Ni coverages the interfacial core-level shift is −100 ± 10 meV. These shifts are analyzed using the partial-shift model of Nilsson et al. [Phys. Rev. B 38 (1988) 10357]; the analysis indicates that the difference in binding energies between …

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Resistivity As Dynamic Behavior In Low Density Polyethylene, J. Brunson, John R. Dennison

All Physics Faculty Publications

Bridging the gap between theoretical calculations and experimental data has been the focus of much of the research into the electrical behavior of insulating polymers. Low density polyethylene is the standard test material used in both experimental work and numerical calculations. Resistivity measurements provide more than an absolute value for technical use; they also provide insight into the nature of active charge carriers and trapping behavior within LDPE.

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Comparison Of Machine Learning Algorithms For Modeling Species Distributions: Application To Stream Invertebrates From Western Usa Reference Sites, Margi Dubal

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Machine learning algorithms are increasingly being used by ecologists to model and predict the distributions of individual species and entire assemblages of sites. Accurate prediction of distribution of species is an important factor in any modeling. We compared prediction accuracy of four machine learning algorithms-random forests, classification trees, support vector machines, and gradient boosting machines to a traditional method, linear discriminant models (LDM), on a large set of stream invertebrate data collected at 728 reference sites in the western United States. Classifications were constructed for individual species and for assemblages of sites clustered a priori by similarity on biological characteristics. …

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Heritability Of Cognition And Memory Loss In The Cache County Memory Study Cohort, Cassidy P. Allen

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

The Cache County Memory Study (CCMS) is a longitudinal study of the elderly in Cache County, Utah, that was initiated over twelve years ago to explore the role of APOE genotype and other environmental factors in dementia risk and cognitive function. Collaboration between the CCMS and investigators with the Utah Population Database (UPDB) at the University of Utah has revealed a significant number of sibships among the original 5,092 CCMS participants, along with complex pedigrees that include additional thousands of ancestors and relatives not enrolled in the Cache Study. Information about these families and pedigrees raises the potential for studies …

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Full-Text Articles in Physical Sciences and Mathematics

Nutrient Loading And Eutrophication In The Great Salt Lake, Wayne A. Wurtsbaugh

Watershed Sciences Faculty Publications

Gravity Has A Story To Tell: Lisa And The Search For Low Frequency Gravitational Waves, Shane L. Larson

Colloquia and Seminars

Usu’S Rayleigh-Scatter Lidar, Vincent B. Wickwar

Presentations

One With The Cosmos: A Short Tour Out Your Backdoor, Shane L. Larson

Public Talks

Seasonal Variations Of Semidiurnal Tidalperturbations In Mesopause Region Temperature And Zonal And Meridional Winds Above Fort Collins, Colorado(40.6°N, 105.1°W), Tao Yuan, H. Schmidt, C. Y. She, D. A. Krueger, S. Reising

All Physics Faculty Publications

Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffman, John R. Dennison, Clint D. Thomson, Jennifer Albresten

All Physics Faculty Publications

Gravity Wave And Tidal Influences On Equatorial Spread F Based On Observations During The Spread F Experiment (Spreadfex), D. C. Fritts, S. L. Vadas, D. M. Riggin, M. A. Abdu, I. S. Batista, H. Takahashi, A. Medeiros, F. Kamalabadi, H. L. Liu, B. G. Fejer, Michael J. Taylor

All Physics Faculty Publications

Temperature And Electric Field Dependence Of Conduction In Low-Density Polyethylene, John R. Dennison, Jerilyn Brunson

All Physics Faculty Publications

Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffmann, Jr Dennison, Clint D. Thomson, Jennifer Albretson

Journal Articles

Deep Dielectric Charging Of Spacecraft Polymers By Energetic Protons, Nelson W. Green, Jr Dennison

Journal Articles

Microtextural Constraints On The Interplay Between Fluidrockreactions And Deformation, Alexis K. Ault, Jane Selverstone

Geosciences Faculty Publications

Seasonal And Longitudinal Dependence Of Equatorialdisturbance Vertical Plasma Drifts, Bela G. Fejer, J. W. Jensen, S. Y. Su

Bela G. Fejer

Movement Strategies Of Seed Predators As Determinants Of Plant Recruitment Patterns, Lorenzo Mari, Renato Casagrandi, Marino Gatto, Tal Avgar, Ran Nathan

Wildland Resources Faculty Publications

On A New Process For Cusp Irregularity Production, Herbert C. Carlson, K. Oksavik, J. Moen

Faculty publications

Vignettes From The World Of Gravitational Wave Astrophysics, Shane L. Larson

Colloquia and Seminars

Songs From The Milky Way: Our Galaxy In Low Frequency Gravitational Waves, Shane L. Larson

Colloquia and Seminars

How Movement Properties Affect Prey Encounter Rates Of Ambush Versus Active Predators: A Comment On Scharf Et Al, Tal Avgar, Nir Horvitz, Luba Broitman, Ran Nathan

Wildland Resources Faculty Publications

Low-Fluence Electron Yields Of Highly Insulating Materials, Ryan Hoffmann, John R. Dennison

All Physics Faculty Publications

Starlight In The Night: Discovering The Secret Lives Of Stars, Shane L. Larson

Public Talks

Richfield Field Office Planning Area - Proposed Resource Management And Final Environmental Impact Statement, United States Department Of The Interior, Bureau Of Land Management

Final environmental Impact Statements (UT)

Moab Field Office Planning Area Proposed Resource Management Plan And Final Environmental Impact Statement, United States Department Of The Interior, Bureau Of Land Management

Final environmental Impact Statements (UT)

Dark Side Of The Universe: Dark Matter In The Galaxy And Cosmos, Shane L. Larson

Public Talks

From Quarks To The Cosmos, Shane L. Larson

Colloquia and Seminars

Whispers From The Cosmos: Seeing The Universe In Gravitational Waves, Shane L. Larson

Colloquia and Seminars

Timing And Cause Of Water Level Fluctuations In Kluane Lake, Yukon Territory, Over The Past 5000 Years, Janice Brahney, John J. Clague, Brian Menounos, Thomas W. D. Edwards

Watershed Sciences Faculty Publications

Rare Measurements Of A Sprite With Halo Event Driven By A Negative Lightning Discharge Over Argentina, Michael J. Taylor, T. Berkey, Pierre-Dominique Pautet, S. A. Cummer, N. Jaugey, J. N. Thomas, N. N. Solorzano, F. Sao Sabbas, R. H. Holzworth, O. Pinto, N. J. Schuch

All Physics Faculty Publications

Core-Level Spectroscopy Of The Ni/W(110) Interface: Correlation Of W Interfacial Core Levelshifts With First-Layer Ni Phases, D. Mark Riffe, R. T. Franckowiak, N. D. Shinn, B. Kim, K. J. Kim, T. H. Kang

All Physics Faculty Publications

Resistivity As Dynamic Behavior In Low Density Polyethylene, J. Brunson, John R. Dennison

All Physics Faculty Publications

Comparison Of Machine Learning Algorithms For Modeling Species Distributions: Application To Stream Invertebrates From Western Usa Reference Sites, Margi Dubal

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Heritability Of Cognition And Memory Loss In The Cache County Memory Study Cohort, Cassidy P. Allen

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023