Physical Sciences and Mathematics Commons^™

Pressure Induced Dynamical Instabilities In Body Center Cubic Crystals, Oscar Guerrero

Open Access Theses & Dissertations

Large-scale atomistic simulations of shock-wave propagation in single crystals exhibit large anisotropies in the elastic-plastic and solid-liquid transitions. Characteristic of this type of simulations are the large strains at which the crystal yields plastically, regardless of crystal orientation. At these large strains, uniaxial deformations, such as those produced in planar shock loading generate dynamical instabilities. We have investigated the directional anisotropy of the elastic limit in bcc crystals, in particular Tantalum (Ta), employing molecular dynamics (MD) simulations. We show that the elastic - plastic transition in BCC defect-free crystals is caused by the appearance of soft-phonon modes and not via …

Tectonic Geomorphology Of The Puna Tsang Chhu, Western Bhutan, Abby May Woody

Open Access Theses & Dissertations

There are two boundaries, or physiographic transitions, between three distinct topographic regions in Bhutan. The southern and northern regions have relatively steep hillslopes and high relief, while the central region has gentle hillslopes and low relief. The geomorphology of a 70-km stretch along the Puna Tsang Chhu valley between the towns of Uma and Amrimo was studied in March and April of 2009 to provide constraints on the active tectonics of western Bhutan and the nature of these physiographic transitions.

The Puna Tsang Chhu valley contains a set of alluvial cut-and-fill and bedrock (strath) river terraces with associated sediments - …

Use Of Cognitive Constructs In Linear Algebra, Azucena Zamora

Open Access Theses & Dissertations

Thesis analyzed the presence of two cognitive entities-- modes of thinking and metonymies and metaphors- in the reasoning of three students enrolled in a first year matrix algebra course at a southwest university via the responses given to a set of eight questions asked during one-on-one interviews. The findings of our analysis shed light on the cognitive constructs that students employ to form their understanding of linear algebra concepts. Furthermore, our findings provide clues about the ways in which students move from one mode of thinking to another in the context of varying levels of exposure to graphical, algebraic, and …

Use Of The Cmaq And Wrf-Chem Models To Investigate Tropospheric Ozone And Particulate Matter In The El Paso-Juarez Airshed, Juan Gustavo Arias Ugarte

Open Access Theses & Dissertations

Ground level ozone pollution is a continuing environmental concern in several U.S cities. A necessary step towards understanding and quantifying the problem is the implementation of numerical models that can predict pollutant concentrations. Simulations were performed using the Community Multiscale Air Quality (CMAQ) and the (Weather Research Forecast/Chemical (WRF-Chem) models to study the tropospheric ozone and particulate matter concentrations in the El Paso-Juarez Airshed and to analyze the influence of U.S and Mexican cities as possible contributors to ground level ozone pollution in this region. This study involves the implementation and validation of both the CMAQ and WRF-Chem models for …

Iron And Manganese Based Nanomaterials For The Removal Of Selenite And Selenate From Aqueous Solution, Christina Marie Gonzalez

Open Access Theses & Dissertations

Selenium, a naturally occurring element in the environment, is an essential nutrient for humans and animals. However, there is a narrow range between selenium deficiency and toxicity. Selenium in natural waters generally has a concentration of < 10 ppb (parts per billion); however, in the San Joaquin Valley of California concentrations of selenium ranging from 140 to 1400 ppb have been observed. Anthropogenic practices such as agricultural irrigation drainage, coal burning power plants, combustion of fossil fuels, and mining operations are increasing selenium concentrations in aqueous environments. Once in aqueous environments, selenium exists primarily as the two inorganic oxoanions selenite (SeO32-) and selenate (SeO42-). Both of these selenium oxoanions are known to bioaccumulate and can cause embryotoxic and teratogenic effects to waterfowl. There has been a variety of treatment technologies developed for remediation of both selenium oxoanions in water including bacterial reduction, membrane filtration, chemical reduction, reverse osmosis, and solar ponds. However, these treatment technologies are not cost efficient. In this study an alternative treatment technique known as adsorption was used with three synthetic nanomaterials consisting of an iron oxide, manganese oxide, and an iron/manganese oxide. The pH profiles, time dependencies, competitive anion effects, and adsorption isotherms were performed with each of the nanomaterials for both selenite and selenate. In addition, X-ray absorption spectroscopy (XAS) studies were performed to determine both the oxidation state and binding coordination of the selenium oxoanion binding to the nanomaterials.

The investigation revealed the non microwave-assisted and microwave-assisted synthetic Fe3O4 and Mn3O4 nanomaterials, as well as the non microwave-assisted synthetic MnFe2O4 nanomaterial had the phases of magnetite, hausmannite, and Jacobsite, while the grain sizes were 27, 25, 25, 34, and 27 nm, respectively. The optimal binding of selenium oxoanions for all nanomaterials examined was reached at pH 4. Both non microwave-assisted and microwave-assisted Fe3O4 …

Modeling Geographic Awareness Of Road Networks For Consistency Verification, Ari Kassin

Open Access Theses & Dissertations

Problems related to transportation and inspection of valuable or sensitive assets such as commercial products and materials, cultural items and works of art, and hazardous materials share similarities and can be modeled by a core set of abstract entities including a payload, a vehicle, a driver, and an inspector. To make the load handling capabilities of security monitoring and inspection systems more scalable, security can be increased by reducing the variability of transportation routes to a finite set of authorized routes between trip origin and destination locations. Then trip anomalies, which are unexpected trip variations, can be used in inspection …

Microstructure And Property Evaluation Of Lifepo4 Thin Films For Application In Microbatteries, Jose Marcos Mares

Open Access Theses & Dissertations

The shortage of fossil fuels and the requirements to produce clean, environmental friendly, efficient, and economical energy are the principal problems in the context of energy technology for current and future generations. Therefore, advanced energy storage and conversion capabilities with higher capacity and efficiency are desired. Currently, there is an enormous interest in the development of high energy density rechargeable batteries for use in domestic applications, automotive industries and portable electronic applications. The present research focuses on the development of LiFePO4 thin films for solid-state thin-film microbatteries. The present effort was performed with a specific purpose of understanding the effect …

Coordination Directed Self Assembly Of Pt/Pd Mono-And Multinuclear Complexes, Robert Moreno

Open Access Theses & Dissertations

This research focuses on the development of mononuclear platinum complexes; multinuclear platinum complexes, both of which self assemble into micelles in the presence of water. This work also involved the synthesis of a reverse micelle that allows for detection of water nanocrystals within a defined size molecular envelope. The novel synthesis of these compounds allows for ligand substitution and the creation of a library of compounds.

Understanding The Promotion Effect: A Density Functional Theory Study Based On High Resolution Transmission Electron Microscopy Images For Mos2-Cobalt Promoted Interfaces, Manuel A. Ramos

Open Access Theses & Dissertations

Many studies had been done in order to understand promotion effect and structure/function in unsupported catalyst. Results indicated that d-electrons play an important role promoting catalytical active sites at the edges of MoS2 catalytically structures. Sulfur removal from crude oil, occurs on the edge of molybdenum di-sulfide (MoS2) nano structures, due to promotion of MoS2 nano structures with nickel or cobalt in sulfur-terminated or molybdenum-terminated edge planes. The promotion leads to formation of so-called CoMoS phase (MoS2/Co9S8) first discovered by meaning of Mössbauer spectroscopy, much more CoMoS phase usually called unsupported catalytical particles, have been topic of great interest in …

Identifying Influential Observations Through The Intraclass Correlation Coefficient, Angel De Jesus Davalos

Open Access Theses & Dissertations

In this thesis, we analyze the performance of adapting the DFBETA statistic for identifying influential observations on the intraclass correlation coefficient under the assumptions of the one-way random effects model. Additionally, we introduce an approach for transforming negative intraclass correlation coefficient estimation values using the method of moments estimator. We apply this method on a data set of repeated blood pressure measurements, after which we will investigate implications of identifying influential observations.

Oxidation Of Dibenzothiophene To Dibenzothiophene Using Metal Nanoparticles Supported On Silica, Karina Castillo

Open Access Theses & Dissertations

Silica and nanoparticles of Pt, Au, and Ag supported on silica were tested for the ability to oxidize dibenzothiophene (DBT) to sulfone. High performance liquid chromatography was used to study the removal of DBT from solution. In addition, X- ray diffraction, infrared spectroscopy and Raman Spectroscopy were used to characterize the product of the oxidation reaction. Further studies involved the use X-ray absorption spectroscopy to characterize the nanoparticle catalysts before and after the oxidation reaction.

To better understand the reaction, silica was synthesized at different pHs using three different acids. The acids used to synthesize the silica were HCl, HNO3, …

Development Of Nanotube Hexaniobate For Photocatalytic Production Of Hydrogen From Water, Saroja Pradhan

Open Access Theses & Dissertations

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A New Photochemical Method For The Preparation Of Amino Acid-α-Phenylthioesters And Peptide-α-Phenylthioesters, Tyrone Hogenauer

Open Access Theses & Dissertations

We describe the development of a novel resin with a photoreactive N-acylnitroindoline linker that allows for the synthesis of amino acid- (in solution) or peptide-α-thioesters using standard Fmoc/t-Bu standard solid phase peptide synthesis (SPPS). Recent advances have shown that the yields of this thioesterification reaction have dramatically increased due to a simple change in the order of addition of reagents. Upon illumination with UV-light, in the presence of N-hydroxybenzotriazole (HOBt), the amino acid- or peptide-α-OBt ester is generated by direct photo-release from the nitroindoline linker with minimal epimerization, followed by reaction with thiophenol in the dark to produce amino acid-α-phenylthioesters …

Incidence Functions, Yiyu Liao

Open Access Theses & Dissertations

In the mid 1960's, the incidence algebra was introduced in the seminal paper of Gian-Carlo Rota. He addressed the importance of the Mobius function in combinatorics. In particular, the incidence algebra of a locally finite poset plays an essentially unifying role in the theory of the Mobius function. One of the significant generalizations is the incidence algebra of a Mobius category introduced by Pierre Leroux. With the help from Mobius category, it was exciting to be able to extend the combinatorial results more broadly than just on posets. Before attempting to study this generalization of the Mobius function, we have …

Development Of Wide Band Gap Semiconductor Materials For Renewable Energy, S.M. Sarif Masud

Open Access Theses & Dissertations

Several new wide band gap semiconductor nanocomposite photocatalytic materials have been synthesized from HTiNbO5 and HNb3O8 for solar energy conversion. As a source of renewable energy, the materials are being tested to produce hydrogen fuel from water via photolysis. The materials have high surface areas, are macroporous, and have flatband potentials suitable for reducing water to create hydrogen. Under visible or ultra violet light, the materials were found to be very promising as hydrogen evolving photocatalysts. As part of the synthesis of the composites, the catalysts also exhibited excellent catalytic activity under UV light for reducing ionic platinum and gold …

Test Case Automation For Specification Patterns System And Composite Propositions, Cuauhtemoc Munoz

Open Access Theses & Dissertations

Specifying software properties is a common activity in the software development process. Software properties are often written in a natural language such as English. However, the ambiguity in natural languages makes validation and verification time-consuming and error-prone. Specifying software properties in formal languages such as Linear Temporal Logic (LTL) or Computation Tree Logic (CTL) enables the use of formal verification tools such as model checkers. Nevertheless, formal languages require software developers to have a strong background in mathematics and logic.

The specification Patterns System (SPS) and Composite Propositions (CPs) use a higher-level abstraction to specify software properties formally. The SPS …

Study Of Pbdes In Wastewater, Water And Sludge Of El Paso Del Norte Border Region Using Sbse Td/Gc-Ms, Beatriz Adriana Rocha-Gutierrez

Open Access Theses & Dissertations

Polybrominated diphenyl ethers (PBDEs) are a group of brominated compounds widely used as flame retardants. PBDEs are structurally similar to polychlorinated biphenyls (PCBs), and appear to act similarly in the environment. Due to their persistence and lipophilicity, PBDEs are found to be bioaccumulated and biomagnified in the food chain. Current research in PBDEs is focused on their occurrences, concentration, fate and transport in the environment, and the impact in the ecosystem and human health. Since PBDEs are not regulated in the USA, large amounts of these harmful chemicals are being dumped indiscriminately into the drainage system. As a result, these …

A Deadline-Driven Epidemic Data Collection Protocol Suitable For Tracking Interpersonnel Rendezvous, Avranil Tah

Open Access Theses & Dissertations

This thesis describes a peer-to-peer wireless data collection algorithm that uses epidemic communication to propagate time-sensitive sequentially sampled data records from sensors toward infrastructure connected upload stations via mobile data mules. These records are labeled with sequence numbers and delivery deadlines, and are transmitted in sequential order. Delivery deadlines enable transmission prioritization and trigger alarms warning of violations.

The sequential ordering of records simplifies the protocols transmission-control and garbage collection mechanisms: only two monotonically increasing scalar sequence indices associated with a particular sensor must be exchanged between peers prior to selecting which records need to be communicated. One of these …

The Impact Of Cartel Related Violence On Ongoing Traumatic Stress And Self-Medication In Young Adults Living Along The U.S./México Border, Thom J. Taylor

Open Access Theses & Dissertations

Ongoing Potentially Traumatic Stress (OPTS) as a result of violence and insecurity along the U.S./México border remains understudied. Many residents of the border may be both indirectly and directly exposed to potentially traumatic events on an ongoing basis, particularly in the city of Cd. Juárez, México. The present study examined the impact of the violence and insecurity on daily traumatic stress levels and the potential for self-medication via alcohol, cigarettes, and illicit drugs within Spanish speaking young adult residents and commuters to Cd. Juárez, Chihuahua, México. Participants (N = 121) completed multiple online reports of location in and travel to …

Preliminary Archaeological Investigations At The Sierra Diablo Cave Site: Paleoindian And Archaic Occupations In Hudspeth County, Texas, Jose Javier Vasquez

Open Access Theses & Dissertations

It is generally rare to find archaeological sites in the Southwest that retain the type of contextual integrity that the Sierra Diablo Cave exhibits. Often times, cave sites such as the one currently studied offer excellent preservation of cultural materials due to the general lack of moisture and isolation from wind and water erosion. The research aimed to determine when the site was occupied as well as the types of activities that were occurring during those occupations. It exhibits an extensive stratigraphic sequence that contains a well pronounced Late Archaic Period assemblage (Strata A and B) and a Late Pleistocene/Early …

Using Soil-Borne Polycyclic Aromatic Hydrocarbons (Pahs) And Organic Carbon In Soil For Projecting Pollution States Of Pahs In Ambient Air, Chika Yamaguchi

Open Access Theses & Dissertations

Polycyclic Aromatic Hydrocarbons (PAHs) are of environmental concern due to their ubiquitous nature, long-range transport, long half-lives, and toxicity. PAHs enter the environment as a consequence of incomplete combustion and cause adverse health effects. Because they are omnipresent pollutants, PAH distribution is not only a local issue, but also a global issue. Therefore, monitoring PAHs in ambient air and identifying their sources and distribution patterns have tremendous importance in assessing public health. However, sampling and analyzing airborne PAHs with conventional methods is time consuming and costly. In addition, an active sampling method remains unfeasible in many cases because it requires …

Stochastic Optimization For Learning-Based Super-Resolution: Algorithms And Applications, Jun Zheng

Open Access Theses & Dissertations

Human beings get much of their information visually and depend on perception of images for many critical tasks, such as object identification, medical image analysis, photography, etc. In many visual-based applications, higher resolution images are required for perceiving and receiving critical information. A high resolution image can contribute to a better identification of a suspect's face, or a more accurate localization of a tumor in a mammogram, or a more pleasing view in high definition television, and so on. However, it is hard to obtain the high resolution images needed for some applications, for example, the cost of sensors increases …

Signature Matrices: The Eigenvalue Problem, Valeria Aguirre Holguin

Open Access Theses & Dissertations

Dealing with matrices can give us a hard time, especially when their dimension is too big, but we also well know how valuable information a matrix may carry, and that is why we study them. When a matrix has a significant number of zeroes we realize how much easier all calculations are. For instance, the product will be simpler to calculate, the determinant, the inverse and even the eigenvalue problem. This thesis provides the description and behavior of a very special kind of matrices which we call signature matrices. A particular feature of these matrices lies in the fact that …

Application Of Copper And Zinc Isotopes To Fingerprint Metal Sources And Identify Attenuation Mechanisms In The Abandoned Waldorf Mine Area, Clear Creek County, Colorado, Suzan Aranda Luna

Open Access Theses & Dissertations

Acid rock drainage (ARD) is caused by the oxidative weathering of sulfide minerals. Sulfur is oxidized by dissolved oxygen or Fe(III) and sulfate ions, metals, and protons are released into the environment. Hence, the pH of nearby water and soils often decreases in response to ARD while metal concentrations increase. Because a large part of the Rocky Mountains of Colorado are highly mineralized (i.e., the Colorado Mineral Belt), ARD is a serious problem in this region. Moreover, the many abandoned mining areas in the Rocky Mountains that include waste rock piles, tailings impoundments, and surface disturbances add to the problem …

Simulation And Optimization Of Ultra Thin Photovoltaics, Jose Luis Cruz-Campa

Open Access Theses & Dissertations

Sandia National Laboratories (SNL) conducts pioneering research and development in Micro-Electro-Mechanical Systems (MEMS) and solar cell research. This dissertation project combines these two areas to create ultra-thin small-form-factor crystalline silicon (c-Si) solar cells. These miniature solar cells create a new class of photovoltaics with potentially novel applications and benefits such as dramatic reductions in cost, weight and material usage.

At the beginning of the project, unusually low efficiencies were obtained in the research group. The intention of this research was thus to investigate the main causes of the low efficiencies through simulation, design, fabrication, and characterization.

Commercial simulation tools were …

The Composition Of Precipitation In El Paso, Texas, Sonny P. Emmert

Open Access Theses & Dissertations

The composition of precipitation reflects the transport of particles from varying air mass source regions as well as input from local environmental and anthropogenic activities. Air research in El Paso, TX, U.S.A/Ciudad Juarez, Chihuahua, Mexico has been traditionally limited to studies of local inputs of air pollution; no transition has been made to studying the scavenging, washout, and transport of pollutants by precipitation. The goal of this research project was to identify transported pollutants in precipitation, and determine if there were any health and ecological implications. The research investigated biological, chemical, and geological constituents in precipitation samples collected between September …

Studies Of Earthquakes Stress Drops, Seismic Scattering, And Dynamic Triggering In North America, Christian Rene Escudero Ayala

Open Access Theses & Dissertations

I use the Relative Source Time Function (RSTF) method to determine the source properties of earthquakes within southeastern Alaska-northwestern Canada in a first part of the project, and earthquakes within the Denali fault in a second part. I deconvolve a small event P-arrival signal from a larger event by the following method: select arrivals with a tapered cosine window, fast fourier transform to obtain the spectrum, apply water level deconvolution technique, and bandpass filter before inverse transforming the result to obtain the RSTF. I compare the source processes of earthquakes within the area to determine stress drop differences to determine …

Chromium(Iii/Vi) Binding To Magnetite (Fe3o4), Hausmannite (Mn3o4), And Jacobsite (Mnfe2o4) Nanomaterials, Jeffrey Edward Hernandez

Open Access Theses & Dissertations

Chromium is a very versatile metal that is used for many applications in the world. Two of the most common ions of chromium that occur naturally are Cr(III) and Cr(VI). These two oxidation states have very different heath effects in living organisms. Cr(III) is relatively non-toxic to living organisms; however, Cr(VI) is very toxic to most living organisms This study was conducted to find a simple and cost effective method to sequester these two common ionic species of chromium from sources of water that are adjacent to or that are affected by other water sources contaminated by these two ions. …

Spectroscopic Analysis Of Tungsten Oxide Thin Films For Sensor Applications, Jose Luis Enriquez Carrejo

Open Access Theses & Dissertations

The objective of this study is targeted toward improving the quality of pure tungsten oxide (WO3) for application to the detection of poisoning gases, especially of H2S. While pure WO3 is a recognized candidate for gas sensing, its characteristics are strongly dependent on the conditions and methods used in its deposition.

Samples of WO3 thin films analyzed in this work were grown on silicon and sapphire substrates using RF magnetron sputtering at a number of different substrate temperatures and Ar:O2 pressure ratios. The properties of the samples were investigated spectroscopically with the goal of determining how variations in the above …

Assessing Annual And Seasonal Spatial Variability Of Ambient Pm10 Using Linear Regression Analysis In A United States-Mexico Urban Sprawl, Mario Ivan Garcia

Open Access Theses & Dissertations

As air quality issues grow progressively in the consciousness of the global community, stakeholders are pressing for epidemiologic studies of air pollution. The effects of chronic exposure to ambient air pollution remain a difficult challenge due to its substantial small-scale spatial variation. Recent approaches to assess intra-urban exposure have employed the use of proximity-based assessment, interpolation methods, emission-meteorological models, dispersions models, and land-use regression (LUR) models.

This thesis assesses the spatial variability of ambient particulate matter (PM10) obtained by five self-governing models for the area of El Paso. Using multiple linear regression analysis five regression-based equations were developed to predict …