Physical Sciences and Mathematics Commons^™

Assessing The Importance Of Nurse Plant Associations To The Growth Of Pre-~Reproductive Yucca Brevifolia, Eric James Chameroy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Facilitation and competition among plant species, in addition to abiotic factors, play an important role in determining plant community structure in arid and semi-arid environments. I conducted a study in Dry Lake Valley, Lincoln County, Nevada, USA to investigate the importance of nurse plant associations to pre-reproductive Yucca brevifolia (Joshua tree). Dry Lake Valley lies within a transition desert between the Mojave and Great Basin Deserts with ecotonal plant communities consisting of species representative of both deserts. A vegetation survey described the communities in which this study was conducted as a Y. brevifolia woodland dominated by an understory of Ephedra …

Chemical And Electronic Structure Of Surfaces And Interfaces In Cadmium Telluride Based Photovoltaic Devices, Douglas Arthur Duncan

UNLV Theses, Dissertations, Professional Papers, and Capstones

The surface and interface properties are of the upmost importance in the understanding, optimization, and application for photovoltaic devices. Often the chemical, electronic, and morphological properties of the films are empirically optimized, however when progress slows, a fundamental understanding of these properties can lead to breakthroughs. In this work, surfaces and interfaces of solar cell-relevant films are probed with a repertoire of X-ray analytical and microanalysis techniques including X-ray photoelectron (XPS), X-ray excited Auger electron (XAES), X-ray emission (XES) spectroscopies, and atomic force (AFM) and scanning electron (SEM) microscopies.

Silicon-based devices currently dominate the solar market, which is rather inflexible …

Optimization Of The Development Process For Air Sampling Filter Standards, Rajah Marie Mena

UNLV Theses, Dissertations, Professional Papers, and Capstones

Air monitoring is an important analysis technique in health physics. However, creating standards which can be used to calibrate detectors used in the analysis of the filters deployed for air monitoring can be challenging. The activity of a standard should be well understood, this includes understanding how the location within the filter affects the final surface emission rate. The purpose of this research is to determine the parameters which most affect uncertainty in an air filter standard and optimize these parameters such that calibrations made with them most accurately reflect the true activity contained inside. A deposition pattern was chosen …

Ecosystem Response To Recent Climate Change In Alpine Environments, Patrick Shawn Sawyer

UNLV Theses, Dissertations, Professional Papers, and Capstones

Recent variations in meteorological conditions indicate the earth’s climate is changing in ways that can impact delicate ecological balances in sensitive regions. These impacts threaten the essential services provided by such ecosystems. Determining how climate changes are affecting the biosphere is essential to adapt and mitigate harmful consequences. In order to mitigate the negative effects of climate change and adapt to shifting ecological resource constraints, it is imperative to locate such changes and determine vulnerability of ecological resources to changing environmental conditions.

Identifying climate driven ecological changes faces numerous challenges given the reliance on vegetation indices as the primary measure …

Alkali-~Activated Fly Ash Binders: Feasibility As A Sustainable Alternative To Ordinary Portland Cement For Pre-~Cast Systems, Kimberly Sierra

UNLV Theses, Dissertations, Professional Papers, and Capstones

Fresh, load-dependent, transport, and durability properties of alkali-activated fly ash mortars were studied. The influences of activator concentration, solution-to-binder ratio, curing condition, activator type, and sodium silicate-to-total solution ratio on the properties of the studied alkali-activated mortars were examined. This study was divided in two phases. The first phase dealt with the use of sodium hydroxide as the sole activator. The second phase of the study was divided into two parts, both of which used a combination of sodium hydroxide and sodium silicate as the activator solution. Part I of phase II used elevated temperature curing conditions, whereas part II …

The Visual Framing Of The Three Cycles Of Climate Control In The New York Times 1851 To Present, Jason Lee Thompson

UNLV Theses, Dissertations, Professional Papers, and Capstones

This research explored the visual framing of climate control in The New York Times through three cycles of media history. Although no peer-reviewed study has explored this specific topic, a wealth of prior communication articles on both the visual and textual aspects of climate change and geoengineering in the media was mined in order to discover the frames present. Once the visual frames of climate control (war, fix, people, and impacts) were revealed a content analysis was conducted in order to see which frame elements were most and least frequent considering the images of climate control. When combining all three …

Architectural Form, Orientation, And Energy For Residential Design In The Southern Nevada Region., Ludwing Vaca

UNLV Theses, Dissertations, Professional Papers, and Capstones

With the population increase, the high demand of energy from the residential sector, as well as the harsh weather conditions of the Las Vegas region, there needs to be careful consideration in the design of new homes. Energy efficiency in a single family residential building can be augmented early in the design process by careful consideration of the building form and orientation. A systematic investigation and analysis was taken to study the effects of five building forms and different orientations along the cardinal points using the software BEopt version 2.4.0.1. To connect the study to real world circumstances, a residential …

Simulation Of An Air Cooled Single-Effect Solar Absorption Cooling System With Evacuated Tube Collectors, Mohsen Jahandardoost

UNLV Theses, Dissertations, Professional Papers, and Capstones

Consistently increasing CO2 emission and ozone depletion from synthetic refrigerants are serious environmental issues challenging the scientific community. Absorption cooling systems give scope of utilizing low grade energy source for generating cooling effect. Solar energy is one of these low grade energy sources and with considering the fact that cooling demand increases with the intensity of solar radiation, solar refrigeration has been considered as a logical solution.

This thesis consists of two different simulation stages, in the first stage, a single effect lithium bromide absorption cooling system with constant cooling capacity is modeled and the effect of ambient and generator …

Designing, Building And Testing A Solar Thermoelectric Generation, Steg, For Energy Delivery To Remote Residential Areas In Developing Regions, Yacouba Moumouni

UNLV Theses, Dissertations, Professional Papers, and Capstones

New alternatives and inventive renewable energy techniques which encompass both generation and power management solutions are fundamental for meeting remote residential energy supply and demand today, especially if the grid is quasi-inexistent. Solar thermoelectric generators can be a cost-effective alternative to photovoltaics for a remote residential household power supply. A complete solar thermoelectric energy harvesting system is presented for energy delivery to remote residential areas in developing regions. To this end, the entire system was built, modeled, and then validated with LTspice simulator software via thermal-to-electrical analogy schemes. Valuable data in conjunction with two novel LTspice circuits were obtained, showing …

Development Of A Decision Support Framework For The Planning Of Sustainable Transportation Systems, Pankaj Maheshwari

UNLV Theses, Dissertations, Professional Papers, and Capstones

With the rapid increase in economic development throughout the world, there is stress on the resources used to support global economy, including petroleum, coal, silver, and water. Currently, the world is consuming energy at an unprecedented rate never seen before. The finite nature of such non-renewable natural resources as petroleum and coal puts pressure on the environmental system, and ultimately reduces the availability of resources for future generations. Hence, it is critical to develop planning and operational strategies that seek to achieve a sustainable use of existing natural resources.

With this motivation, this dissertation focuses to develop a decision support …

Stable Isotope Analysis Of Bison Latifrons And Paleoecological Inferences, Fabian Ceron Hardy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Bison latifrons was a large Pleistocene herbivore that is traditionally hypothesized to have been adapted to living in forest openings and woodlands. According to this view, the species was primarily a browser of high-growing, woody plants. Very little isotopic work has been conducted on this species, and there have been no prior studies of high altitude localities containing this species. This study aims to address both of these issues.

B. latifrons is known from sites in several states, including California, Idaho, Colorado, Nevada, and Florida, among others. These sites provide diverse examples of this species’ habitat and the opportunity to …

The Presence Of Clostridium Difficile On Environmental Surfaces In Healthcare Facilities Pre- And Post-Decontamination Of Patient Rooms, Theresa Trice

UNLV Theses, Dissertations, Professional Papers, and Capstones

Healthcare-associated infections (HAIs) are infections related to receiving medical care. HAIs are responsible for an excess of morbidity and mortality among hospitalized patients. Though most HAIs rates are on the decline, Clostridium difficile infection rates are at an all-time high, primarily due to the persistence of C. difficile spores in the environment. In the United States, Clostridium difficile-related mortality rates per million have increased from 5.7 in 1999 to 23.7 in 2004, with an estimated 26,642 deaths due to Clostridium difficile infections (CDIs). Clostridium difficile is transmitted via the fecal-oral route or aerosolized endospores, but it can also be transmitted …

Burdens And Benefits Of Climate Change Solutions: A Case Study Of Climate Change Skeptics And Deniers In Rural Nevada, Patricia Dutcher

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation is an ethnographic case study of climate change Doubtfuls and Dismissives with the purpose of understanding their perceptions of water use and renewable energy in the context of a changing climate. I also investigate the information sources and messages they use to understand climate change and climate change solutions. The Global Warming's Six Americas project identifies climate change Doubtfuls and Dismissives as one third of the American public, and an active voice in US climate change policy (Maibach et al, 2009; Leiserowitz et al., 2014). Doubtfuls are people with skeptical attitudes towards anthropogenic climate change, while Dismissives deny …

Lead Hazard Control In Henderson, Nevada: Identifying Critical Areas And The Associated Costs, Khaye Gerazel Arcilla Rufin

UNLV Theses, Dissertations, Professional Papers, and Capstones

Lead poisoning is a common, yet preventable childhood health problem in the United States today. Studies show statistically significant (p < .05) associations between higher childhood lead exposure and subsequent negative developmental outcomes. Since 1993, the U.S. Department of Housing and Urban Development (HUD) Lead Hazard Control (LHC) Grant Program has devoted more than $1 billion in funding to several cities.

This study investigated a total of n=75 homes enrolled into the Henderson Lead Hazard Control and Healthy Homes Program (HLHCHHP) from December 2013 – February 2015. A logistic regression was performed to ascertain the frequency of lead-based paint (LBP) found in homes based on the year it was constructed. Of the 75 enrolled and tested for LBP, 58 homes (77.3%) were found to contain LBP and 17 homes (22.7%) did not contain LBP. The significance value of p=0.013 shows that …

Impacts Of Ozone Dose And Empty Bed Contact Time On Total Organic Carbon Removal Through Ozone-Biological Activated Carbon Treatment, Ashley Selvy

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the face of climate change, pollution, and population growth, water scarcity has become a global threat. Many populations have witnessed their drinking water sources dwindle to an unsustainable level. These severe conditions have sparked interest in potable reuse as an increasingly viable alternative to typical ‘pristine’ drinking water sources. Currently, the California Division of Drinking Water (DDW) provides the most stringent requirements for reuse water quality. The best way to meet these standards is through the use of full advanced treatment (FAT), which consists of reverse osmosis (RO) and an advanced oxidation process (AOP). Alternative treatment trains composed of …