Physical Sciences and Mathematics Commons^™

Statistical Variation Of Diverse Light Emission Measurements From Bisphenol/Amine Epoxy Under Energetic Electron Bombardment, Justin Christensen

Physics Capstone Projects

Dielectric materials subjected to energetic electron fluxes can emit light in several forms. We have observed three distinct types of emissions: (i) short-duration (<1 ms), high-intensity electrostatic discharge (ESD) or “arc” events; (ii) intermediate-duration, high-intensity events which begin with a bright arc followed by an exponential decay of intensity (~10 to 100 s decay constant), termed “flares”; and (iii) long-duration, low-intensity emission, or cathodoluminescence, that continues as long as the electron flux is on. These events were studied for bulk samples of bisphenol/amine epoxy, using an electron gun with varying current densities (0.3 to 5 nA/cm2) and energies (12 to 40 keV) in a high vacuum chamber. Light emitted from the samples was measured with a high-sensitivity visible to near-infrared video camera. Results of the spatial and temporal extent for each type of event are presented as well as a discussion of how absolute spectral radiance and rates for each type of event are dependent on incident electron current density, energy, and power density and on material type, temperature, and thickness. Applications of this research to spacecraft charging and light emissions are discussed.

Statistical Variation Of Diverse Light Emission Measurements From Bisphenol/Amine Epoxy Under Energetic Electron Bombardment, Justin Christensen

Senior Theses and Projects

No abstract provided.

Pleistocene Relative Sea Levels In The Chesapeake Bay Region And Their Implications For The Next Century, Benjamin D. Dejong, Paul R. Bierman, Wayne L. Newell, Tammy M. Rittenour, Shannon A. Mahan, Greg Balco, Dylan H. Rood

Geosciences Faculty Publications

Today, relative sea-level rise (3.4 mm/yr) is faster in the Chesapeake Bay region than any other location on the Atlantic coast of North America, and twice the global average eustatic rate (1.7 mm/yr). Dated interglacial deposits suggest that relative sea levels in the Chesapeake Bay region deviate from global trends over a range of timescales. Glacio-isostatic adjustment of the land surface from loading and unloading of continental ice is likely responsible for these deviations, but our understanding of the scale and timeframe over which isostatic response operates in this region remains incomplete because dated sea-level proxies are mostly limited to …

Variation Of The Linear Biconformal Action, James Thomas Wheeler

All Physics Faculty Publications

We find the field equations of biconformal space in a basis adapted to Lagrangian submanifolds on which the restriction of the Killing metric is non-degenerate.

Studies In Torsion Free Biconformal Spaces. Case 2: \Gamma_{-} = 0, James Thomas Wheeler

All Physics Faculty Publications

We show that the solutions for the symmetric part of the connection in homogeneous biconformal space also satisfy the more general field equations of curved biconformal spaces in the case when \gamma_{-} = 0.

A Rank 7 Pfaffian System On A 15-Dimensional Manifold With F4 Symmetry Algebra, Ian M. Anderson

Tutorials on... in 1 hour or less

Let I be a differential system on a manifold M. The infinitesimal symmetry algebra of I is the set of all vectors fields X on M such that preserve I. In this worksheet we present an example, due to E. Cartan of a rank 7 Pfaffian system on a 15-dimensional manifold whose infinitesimal symmetry algebra is the split real form of the exceptional Lie algebra f4 .

Cartan Involutions And Cartan Decompositions Of A Semi-Simple Lie Algebra, Ian M. Anderson

Tutorials on... in 1 hour or less

In this worksheet we shall review the basic definitions and properties of Cartan involutions and Cartan decompositions and illustrate these using the DifferentialGeometry software package for Lie algebras.

Studies In Torsion Free Biconformal Spaces, James Thomas Wheeler

All Physics Faculty Publications

We study whether the solutions for the symmetric part of the connection in homogeneous biconformal space also satisfy the more general field equation of curved biconformal spaces. We show that the six field equations for the torsion and co-torsion are satisfied by vanishing torsion together with the Lorentzian form of the metric when γ+ = 0.

Individual-Based Modeling: Mountain Pine Beetle Seasonal Biology In Response To Climate, Jacques Regniere, Barbara J. Bentz, James A. Powell, Remi St-Amant

Mathematics and Statistics Faculty Publications

Over the past decades, as significant advances were made in the availability and accessibility of computing power, individual-based models (IBM) have become increasingly appealing to ecologists (Grimm 1999). The individual-based modeling approachprovides a convenient framework to incorporate detailed knowledge of individuals and of their interactions within populations (Lomnicki 1999). Variability among individuals is essential to the success of populations that are exposed to changing environments, and because natural selection acts on this variability, it is an essential component of population performance. © Springer International Publishing Switzerland 2015.

Electrical Properties Of Annealed And Coated Boron Nitride Under Electron Beam Irradiation, Kevin Guerch, Theirry Paulmier, Jr Dennison, Justin Dekany, Pascal Lenormand, Sophie Guillemet-Fritsch

Journal Articles

The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminium oxide (BN/Al₂O₃) coating, and thermally-annealed alumina-coated boron nitride (an-BN/Al₂O₃) were investigated under low power electron irradiation (5 < E₀ < 20 keV, J_i = 10 nA.cm^-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an–BN/Al₂O₃ sample was carried out …

Defects Density Of States Model Of Cathodoluminescent Intensity And Spectra Of Disordered Sio2, Amberly Evans Jensen, Jr Dennison

Journal Articles

Electron beam measurements show that disordered SiO₂ exhibits electron-induced luminescence, and that it varies with incident beam energy and current density, sample temperature, and wavelength. A simple model based on the electronic band structure and defect density of states—initially used to explain electron transport in highly disordered insulating materials—has been extended to predict the relative cathodoluminescent intensity and spectral radiance for disordered SiO₂ as a function of these variables. Due to the large band gap of insulating SiO₂, thermal excitation from the valence to conduction band is highly improbable; excitation is through collisions of the incident …

Variations In Cathodoluminescent Intensity Of Spacecraft Materials Exposed To Energetic Electron Bombardment, Justin Dekany, Justin Christensen, Jr Dennison, Amberly Evans Jensen, Gregory Wilson, Todd Schneider, Charles W. Bowers, Robert Meloy

Journal Articles

Many contemporary spacecraft materials exhibit cathodoluminescence when exposed to electron flux from the space plasma environment. A quantitative, physics-based model has been developed to predict the intensity of the total glow as a function of incident electron current density and energy, temperature, and intrinsic material properties. We present a comparative study of the absolute spectral radiance for more than 20 types of dielectric and composite materials based on this model which spans more than three orders of magnitude. Variations in intensity are contrasted for different electron environments, different sizes of samples and sample sets, different testing and analysis methods, and …

Dynamic Interplay Between Spacecraft Charging, Space Environment Interactions And Evolving Materials, Jr Dennison

Journal Articles

While the effects on spacecraft charging from varying environmental conditions and from the selection of different construction materials have been studied extensively, modification of materials properties by exposure to the space plasma environment can also have profound effects on spacecraft charging. Given the increasingly demanding nature of space missions, there is a clear need to extend our understanding of the dynamic nature of material properties that affect spacecraft charging and to expand our knowledgebase of materials’ responses to specific environmental conditions so that we can more reliably predict the long term response of spacecraft to their environment. This paper focuses …

Electrostatic Discharge And Endurance Time Measurements Of Spacecraft Materials: A Defect-Driven Dynamic Model, Allen Andersen, Jr Dennison, Alec Sim, Charles Sim

Journal Articles

Electrostatic breakdown leads to the majority of anomalies and failures attributed to spacecraft interactions with the plasma space environment. It is therefore critical to understand how electrostatic field strength (F_ESD) of spacecraft materials varies due to environmental conditions such as duration of applied electric field, rate of field change, history of exposure to high fields, and temperature. We have developed a dual-defect, thermodynamic, mean-field trapping model in terms of recoverable and irrecoverable defect modes to predict probabilities of breakdown. Fits to a variety of measurements of the dependence of F_ESD of insulating polymers on endurance time, voltage …

Electrical Properties Study Under Electron Beam Of Annealed And Coated Boron Nitride, Kevin Guerch, Thierry Paulmier, Jr Dennison, Justin Dekany, Sophie Guillemet-Fritsch, Pascal Lenormand

Journal Articles

The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminum oxide (BN/Al₂O₃) coating, and thermally-annealed alumina-coated boron nitride (an–BN/Al₂O₃) were investigated under low power electron irradiation (5 < incident energy E₀ < 20 keV and incident flux J_i = 10 nA.cm^-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an–BN/Al₂O₃ sample was carried out …

Radar Detection Of Ultra High Energy Cosmic Rays: Searching For Coincident Events With Telescope Array Radar And Surface Detectors, Zachary Gibson, Rasha Abbasi, John Belz

Presentations

No abstract provided.

Defining Terms: Greywater, Blackwater And Clearwater, Roslynn Brain, Jeremy Lynch, Kelly Kopp

Natural Resources

Why irrigate with treated drinking water when you can meet your irrigation needs through an effective greywater system?

What is greywater*? Greywater includes all wastewater generated in the home, except toilet water (which is considered “blackwater”). In Utah, kitchen sink and dishwasher water are also categorized as “blackwater”. Greywater is an abundant resource in both residential and commercial buildings. According to Brad Lancaster of the Watershed Management Group in Tucson, Arizona, “greywater harvesting is the practice of directing greywater to the primary root zone (top 2 feet or 0.6m of the soil) of perennial plants to help grow beautiful and …

Linkages Between Water Challenges And Land Use Planning In Megacities, Enjie Li, Joanna Endter-Wada, Shujuan Li

Joanna Endter-Wada

No abstract provided.

A Systems-Based Approach To Address Unintended Consequences Of Demand-Driven Transportation Planning In National Parks And Public Lands, Steven Lawson, Peter Newman, Christopher Monz

Christopher Monz

No abstract provided.

Fe Protein-Independent Substrate Reduction By Nitrogenase Mofe Protein Variants, Karamatullah Danyal, Andrew J. Rasmussen, Stephen M. Keable, Boyd S. Inglet, Studipta Shaw, Oleg A. Zadvornyy, Simon Duval, Dennis R. Dean, Simone Raugei, John W. Peters, Lance C. Seefeldt

Chemistry and Biochemistry Faculty Publications

The reduction of substrates catalyzed by nitrogenase normally requires nucleotide-dependent Fe protein delivery of electrons to the MoFe protein, which contains the active site FeMo cofactor. Here, it is reported that independent substitution of three amino acids (β- 98Tyr→His, α-64Tyr→His, and β-99Phe→His) located between the P cluster and FeMo cofactor within the MoFe protein endows it with the ability to reduce protons to H2, azide to ammonia, and hydrazine to ammonia without the need for Fe protein or ATP. Instead, electrons can be provided by the low-potential reductant polyaminocarboxylate-ligated Eu(II) (Em values of −1.1 to −0.84 V vs the normal …

Impact Of Detergent On The Biophysical Properties And Immune Response Of The Ipadb Fusion Protein, A Candidate Subunit Vaccine Against Shigella Spp., X. Chen, S. P. Choudhari, F. J. Martinez-Becerra, J. H. Kim, N. E. Dickenson, R. T. Toth, S. B. Joshi, J. C. Greenwood, J. D. Clements, W. D. Picking, C. R. Middaugh, W. L. Picking

Chemistry and Biochemistry Faculty Publications

Shigella spp. are causative agents of bacillary dysentery, a human illness with high global morbidity levels, particularly among elderly and infant populations. Shigella infects via the fecal-oral route, and its virulence is dependent upon a type III secretion system (T3SS). Two components of the exposed needle tip complex of the Shigella T3SS, invasion plasmid antigen D (IpaD) and IpaB, have been identified as broadly protective antigens in the mouse lethal pneumonia model. A recombinant fusion protein (DB fusion) was created by joining the coding sequences of IpaD and IpaB. The DB fusion is coexpressed with IpaB's cognate chaperone, IpgC, for …

Electrodeposited Cobalt-Phosphorous-Derived Films As Competent Bifunctional Catalysts For Overall Water Splitting, Nan Jiang, Bo You, Meili Sheng, Yujie Sun

Chemistry and Biochemistry Faculty Publications

One of the challenges to realize large-scale water splitting is the lack of active and low-cost electrocatalysts for its two half reactions: H2 and O2 evolution reactions (HER and OER). Herein, we report that cobalt-phosphorous-derived films (Co-P) can act as bifunctional catalysts for overall water splitting. The as-prepared Co-P films exhibited remarkable catalytic performance for both HER and OER in alkaline media, with a current density of 10 mAcm¢2 at overpotentials of ¢94 mV for HER and 345 mV for OER and Tafel slopes of 42 and 47 mV/dec, respectively. They can be employed as catalysts on both anode and …

Introduction Effort, Climate Matching And Species Traits As Predictors Of Global Establishment Success In Non-Native Reptiles, Peter J. Mahoney, Karen H. Beard, Andrew M. Durso, Aimee G. Tallian, Arin Lexine Long, Ryan J. Kindermann, Nicole E. Nolan, Daniel Kinka, Harrison E. Mohn

Biology Faculty Publications

Non-native reptiles are often detrimental to native communities and ecosystems and can be extremely difficult to manage once established. Thus, there is considerable interest in predicting the likelihood of establishment of nonnative reptiles. We assessed three hypotheses describing possible factors contributing to the successful establishment of introduced reptiles in an effort to better identify potential invaders.

Response Of Stomatal Density And Bound Gas Exchange In Leaves Of Maize To Soil Water Deficit, Wensai Zhao, Yonglin Sun, Roger Kjelgren, Xiping Liu

Plants, Soils, and Climate Faculty Publications

Stomatal behavior in response to drought has been the focus of intensive research, but less attention has been paid to stomatal density. In this study, 5-week-old maize seedlings were exposed to different soil water contents. Stomatal density and size as well as leaf gas exchange were investigated after 2-, 4- and 6-weeks of treatment, which corresponded to the jointing, trumpeting, and filling stages of maize development. Results showed that new stomata were generated continually during leaf growth. Reduced soil water content significantly stimulated stomatal generation, resulting in a significant increase in stomatal density but a decrease in stomatal size and …

Decadal Oscillation Of Autumn Precipitation In Central Vietnam Modulated By The East Pacific-North Pacific (Ep-Np), R. Li, Shih-Yu (Simon) Wang, R. R. Gillies, B. Buckley, L. H. Troung, C. Cho

Plants, Soils, and Climate Faculty Publications

Autumn precipitation over Central Vietnam is associated with an increase in the occurrence of tropical cyclones that lead to frequent flooding and pose a significant threat to lives and property. The present analyses reveal a pronounced decadal oscillation of autumn precipitation in Central Vietnam within the 8-11 year frequency band that is modulated by the East Pacific-North Pacific (EP-NP) teleconnection. The negative phase of the EP-NP pattern is associated with a positive sea surface temperature (SST) anomaly in the South China Sea (SCS) that induces low-level convergence, enhances convection, and increases precipitation over Central Vietnam and adjacent islands including Hainan …

Anthropogenic Footprint Of Climate Change In The June 2013 Northern India Flood, C. Cho, R. Li, Shih-Yu (Simon) Wang, J. -H. Yoon, R. R. Gillies

Plants, Soils, and Climate Faculty Publications

During 13-17 June 2013, heavy rainfall occurred in the northern Indian state of 15 Uttarakhand and led to one of the worst floods in history and massive landslides, 16 resulting in more than 5,000 casualties and a huge loss of property. In this study, 17 meteorological and climatic conditions leading up to this rainfall event in 2013 and 18 similar cases were analyzed for the period of 1979-2012. Attribution analysis was 19 performed to identify the natural and anthropogenic influences on the climate anomalies 20 using the historical single-forcing experiments in the Coupled Model Intercomparison 21 Project Phase 5 (CMIP5). …

A Combined Dynamical And Statistical Downscaling Technique To Reduce Biases In Climate Projections: An Example For Winter Precipitation And Snowpack In The Western United States, R. Li, Shih-Yu (Simon) Wang, R. R. Gillies

Plants, Soils, and Climate Faculty Publications

Large biases associated with climate projections are problematic when it comes to their regional application in the assessment of water resources and ecosystems. Here, we demonstrate a method that can reduce systematic biases in regional climate projections. The global and regional climate models employed to demonstrate the technique are the Community Climate System Model (CCSM)and the Weather Research and Forecasting (WRF) model. The method first utilized a statistical regression technique and a global reanalysis dataset to correct biases in the CCSM-simulated variables (e.g., temperature, geopotential height, specific humidity, and winds) that are subsequently used to drive the WRF model. …

Gauge Transformations Of The Biconformal Connection, James Thomas Wheeler

All Physics Faculty Publications

We study the changes of the biconformal gauge fields under the local rotational and dilatational gauge transformations.

Chalcogen Bonds In Complexes Of Soxy (X, Y = F, Cl) With Nitrogen Bases, Luis Miguel Azofra, Ibon Alkorta, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

SOF2, SOFCl, and SOCl2 were each paired with a series of N bases. The potential energy surface of the binary complexes were characterized by MP2 calculations with double and triple-ξ basis sets, extrapolated to complete sets. The most stable configurations contained a S···N chalcogen bond with interaction energies as high as 6.8 kcal/mol. These structures are stabilized by a Nlp→σ*(S−Z) electron transfer (Z = O, F, Cl), complemented by Coulombicattraction of N to theσ-hole opposite the Z atom. N···S−F and N···S−Cl chalcogen bonds are stronger than N···S = O interactions.Formation of each chalcogen bond elongates all of the internalcovalent bonds …

Rainich-Type Conditions For Perfect Fluid Spacetimes, Dionisios Krongos, Charles G. Torre

Research Vignettes

In this worksheet we describe and illustrate a relatively simple set of new Rainich-type conditions on an n-dimensional spacetime which are necessary and sufficient for it to define a perfect fluid solution of the Einstein field equations. Procedures are provided which implement these Rainich-type conditions and which reconstruct the perfect fluid from the metric. These results provide an example of the idea of geometrization of matter fields in general relativity, which is a purely geometrical characterization of matter fields via the Einstein field equations.