Digital Commons Network^™

Numerical Simulations Of Directed Self-Assembly Methods In Di-Block Copolymer Films For Efficient Manufacturing Of Nanoscale Patterns With Long-Range Order, Joseph Hill

Graduate Theses and Dissertations

Directed self-assembly (DSA) of block copolymers (BCPs) has been shown as a viable method to achieve bulk fabrication of surface patterns with feature sizes smaller than those available through traditional photolithography. Under appropriate thermodynamic conditions, BCPs will self-assemble into ordered micro-domain morphologies, a desirable feature for many applications. One of the primary interests in this field of research is the application of thin-film BCPs to existing photolithography techniques. This “bottom-up” approach utilizes the self-assembled BCP nanostructures as a sacrificial templating layer in the lithographic process.

While self-assembly occurs spontaneously, extending orientational uniformity over centimeter-length scales remains a critical challenge. A …

Application Of Percentage Within Limits Concepts On A Balanced Mix Design Of Asphalt Mixtures, Elvis Alexander Castillo Camarena

Graduate Theses and Dissertations

Many agencies have incorporated rutting, and more recently cracking, laboratory test requirements in the design process of asphalt mixtures. The objective of each additional specification is to produce a balance between the stability and durability of the final product. Although a performance-engineered mixture design (PEMD), denoted here as a balanced mix design (BMD), offers compelling benefits, there is concern regarding the compatibility of the BMD with current construction practices. The objective of this work is to correlate a BMD method with realistic binder content construction tolerances by applying the concepts of a percent-within-limits (PWL) approach to field QC/QA. First, Chapter …

Behavior Of Concrete Structures Reinforced With High Strength Steel, Rahman S. Kareem

Graduate Theses and Dissertations

The structural strength and corrosion resistance of concrete members are improved when A1035 steel is used as the main reinforcement. The enhancement of A1035 is achieved by the modification of the composition and microstructure of the steel. Therefore, the behavior of concrete structures reinforced with high-performance steel (A1035) is different from those reinforced with the regular steel (A615). Concrete bridge decks reinforced with different amounts of A1035 were studied in this research program. The structural behavior of twelve concrete bridge decks reinforced with A615 Grade 420 (60 ksi) and A1035 Grade 830 (120 ksi) steel was investigated at both service …

A Methodological Framework To Evaluate Community Perceptions Of Economic And Safety Impacts Attributed To Highway Bypass And Widening Projects, Karla Diaz-Corro

Graduate Theses and Dissertations

Transportation practitioners have proposed the construction of highway bypass and widening projects in rural communities to address traffic-related problems that include noise pollution and congestion, among others. In the past, the construction of bypass projects has led community residents to raise concerns about potential decreases in business activity for businesses located along the bypassed road. For transportation organizations, it is essential to understand the economic, social, and safety impacts of transportation projects in terms of public perceptions as public input is a required part of the project planning phase. Moreover, it is recommended that agencies perform retrospective analyses of project …

Mechanical And Frictional Behavior Of Textured And Non-Textured Surfaces, Raghuram R. Santhapuram

Graduate Theses and Dissertations

Tribology is the study of surfaces where two objects are sliding against another. Significant energy is lost due to friction between the sliding surfaces. Therefore, developing or designing surfaces to minimize friction is critical for the durability and reliability of the mechanical components. Several researchers have identified that surface texturing at the nanoscale (nanotexture) would reduce the friction between the contacting surfaces. The nanotextured surfaces have several applications in microelectromechanical systems and nanoelectromechanical systems. This dissertation employs molecular dynamics simulations to investigate the frictional and mechanical response of nanotextured aluminum (Al) and Al/amorphous silicon (a-Si) composite surfaces.

This study determines …

Moisture Monitoring Of A Clt Structure In A Southern Climate, Elizabeth Poblete

Graduate Theses and Dissertations

Understanding of moisture behavior in cross laminated timber (CLT) is critical to the widespread use of CLT in construction in the United States. Currently, very little data exists on the long-term impact of moisture on CLT. The objective of this research is to collect data regarding the long-term moisture variation in the CLT panel at the University of Arkansas Adohi Hall residence hall. The climate of Northwest Arkansas is different from previously monitored buildings, as they were in the Pacific Northwest. Comparatively, Northwest Arkansas has a warmer climate with higher average annual precipitation. Waterproofing efforts are usually employed to prevent …

Adhesion And Deformation Mechanisms Of Polydopamine And Polytetrafluoroethylene: A Multiscale Computational Study, Matthew Brownell

Graduate Theses and Dissertations

Polydopamine (PDA) has been shown to bond via covalent bonding, van der Waals forces, and hydrogen bonding and is known to adhere strongly to almost any material. The application of PDA between a substrate and a PTFE surface coating has resulted in low friction and a greatly reduced wear rate. Previous research probing the capabilities and limitations of PDA/PTFE films have studied the wear and mechanical properties of the film, but the overall adhesive and deformation mechanisms remain unclear.

In this research, we investigate the tribological properties of PDA and PTFE molecules and composites from the atomic to the microscale …

Cement Stabilized Crushed Stone Base Course Strength And Stiffness Analysis, Andrew Deschenes

Graduate Theses and Dissertations

Approximately 70 – 80% of state departments of transportations (DOTs) utilize the 1993 AASTHO Guide for Design of Pavement Structures (1993 AASHTO) [1] for structural design of pavements. A growing portion of DOT’s are beginning to implement the Mechanistic-Empirical Pavement Design Guide (MEPDG), referred to as AASHTOWare Pavement ME [2]. The 1993 AASHTO flexible guide applies empirically derived unitless strength values referred to as structural layer coefficients and structural numbers (SN) to pavement thickness and pavement types. The 1993 AASHTO rigid flexible guide utilizes the depth and strength of the concrete pavement, with the composite spring constant (kc), which is …

An Investigation Into The Effects Of Fly Ash On Freeze-Thaw Durability Prediction, Yancy Schrader

Graduate Theses and Dissertations

Air is purposefully entrained into concrete primarily to improve resistance to freeze-thaw deterioration while saturated with water. Air entraining admixtures (AEAs) are chemical admixtures designed to entrain air into the concrete to provide adequate resistance to the effects of freezing and thawing. One of the challenges associated with air entrainment in concrete is the interaction of an AEA with supplementary cementitious materials present in the concrete, particularly fly ash. Fly ash is a by-product of the coal fired electrical generation industry, and often contains residual unburned carbon and other components that can increase the AEA demand of a particular concrete …

Effect Of Citric Acid On Slump, Compressive Strength, And Setting Time Of Belitic Calcium Sulfoaluminate Concrete, Israel Aguilar Rosero

Graduate Theses and Dissertations

Belitic calcium sulfoaluminate (BCSA) cement has well established advantages related to fast setting time, fast strength gain, long-term strengths, shrinkage, and sustainability. Due to its fast setting and hardening, this type of cement has historically been used to repair concrete structures, highways, and runways. This work provides much needed guidance on establishing mix design criteria for BCSA cement. Guidance is also given on the effects of set retarders on strength, slump, and setting times. Citric acid and a phosphonic acid-based admixture were tested as retarders for different concrete mixtures. Three studies were performed. In the slump study five different water …

Using Bcsa Cement To Repair Waterway Transportation Structures, Anazaria Johanis Ortega Gonzalez

Graduate Theses and Dissertations

Many maritime structures (e.g., locks, dams, ports) in the US are either reaching or are past their design lives, and there are limited funds for the necessary maintenance activities which can lead to repairs that requires closures. These structures are not easy to detour and often require dewatering before repairs can be made, closures can cause delays and business-related losses which can have a large effect on the nation’s economy. Thus, it is advantageous to reduce the repair time for maritime structures. BCSA (belitic calcium sulfoaluminate) cement is a promising material to perform this type of repair due to its …

Seismic Loading Effects Within Orthogonally Connected Steel Lateral Force Resisting Systems, Alhussin Faraj Aliwan

Graduate Theses and Dissertations

Steel buildings located within seismically active regions require special design considerations to ensure public safety and prevent collapse during an extreme seismic event. Two commonly used steel systems are special moment frames (SMFs) and buckling-restrained braced frames (BRBFs). When two seismic systems share a common column in an orthogonal configuration (such as at a building corner), design specifications currently consider a 100+30 rule wherein the shared column is designed for 100% fuse demand in one direction, plus 30% fuse demand from the other direction. While this rule has been shown to be reasonable for elastic building response, a few studies …

Leveraging Biomimicry And Additive Manufacturing To Improve Load Transfer In Brittle Materials, Ana Paula Bernardo

Graduate Theses and Dissertations

With the emergence of Additive Manufacturing (i.e., 3D printing) in construction, new strategically designed shapes can be created to improve load transfer through structural members and foundations. Cross-sections can be optimized to carry load using less material, or even using weaker constituent materials, like soils, which are cheap and abundant. The goal of this research is to investigate the benefits of using cellular patterns which leverage biomimicry in civil engineering applications, since nature has perfectly engineered materials and patterns which carry loads with the least amount of material possible. Most of the periodic cellular work to date has focused on …

The Virome Of Peony And The Population Structure Of Its Most Prominent Viruses, Cullen Shaffer

Graduate Theses and Dissertations

Peony (Peonia lactiflora, Pall.) is a popular ornamental that has been cultivated for millennia. Due to its popularity, plant material is frequently moved across international borders allowing for the spread of viruses. The virome of several peony plants was investigated and four viruses; namely Amazon lily mild mottle virus (ALiMMV), Cycas necrotic stunt virus (CNSV), Gentian Kobu-sho associated virus (GKaV) and Lychnis mottle virus (LycMoV) were detected for the first time in the Western Hemisphere. Incidence ranged from a few plants for ALiMMV to near universal infection for CNSV. GKaV was found in individuals that were infected with Lemoine’s disease …

Parallel Strategies To Control Bacterial Panicle Blight Of Rice, Laura Ortega

Graduate Theses and Dissertations

Bacterial Panicle Blight (BPB) of rice is a seed-borne disease caused by the bacterium Burkholderia glumae. This disease has affected rice production worldwide and its effects are likely to become more devastating with the continuous increase in global temperatures especially during the growing season. Field data has shown that the disease has been more prevalent in years when the temperatures have been unusually high especially at night possibly due to the bacterial adaptation to grow at temperatures higher than 40oC. With the continuous rise in global temperatures, it is likely that this disease will be more problematic. The bacterium can …

Design, Fabrication, And Reliability Effects Of Additively Manufactured First Level Compliant Interconnects For Microelectronics Application, Tumininu David Olatunji

Graduate Theses and Dissertations

Semiconductor packaging and development is greatly dependent on the magnitude of interconnect and on-chip stress that ultimately limits the reliability of electronic components. Thermomechanical related strains occur because of the coefficient of thermal expansion mismatch from different conjoined materials being assembled to manufacture a device. To curb the effect of thermal expansion mismatch between conjoined parts, studies have been done in integrating compliant structures between dies, solder balls, and substrates. Initial studies have enabled the design and manufacturing of these structures using a photolithography approach which involves a high number of fabrication steps depending on the complexity of the structures …

Assimilating Through Consumption: A Rhetorical History Of The Early Years Of The Advocate, Cora Beth Butcher-Spellman

Graduate Theses and Dissertations

This thesis uses analysis of constitutive rhetoric and queer archival methods to examines how The Advocate used assimilationist rhetoric and consumerist rhetoric in fundamentally anti-democratic ways to consolidate the form of ideal gay consumer-citizenship. Focusing on the first three years of the publication, I utilize queer theory and theories of citizenship and political economy to explain how The Advocate’s rhetoric and mainstream success allowed the publication to normalize a limited and politically weak gay identity. This thesis argues The Advocate’s rhetoric of exclusion, authority, and consumerism were three central features shaping ideal gay consumer-citizenship as most available to people who …

A Snapshot Semester: Students’ Reflections Of Performance And Mental State Throughout A Graduate Course, Bradley D. Borges

Graduate Theses and Dissertations

Graduate students are anecdotally reputed to be among the most stressed groups of young adults. Common sources of stress for graduate students have included coursework, assistantships, finances, career preparation, and family (Wyatt & Oswalt, 2013; Mazzola, Walker, Shockley & Spector, 2011; Oswalt & Riddock, 2007). Guided reflection can be used by educators to assist students in both learning (Boud, Keogh & Walker, 2013; Kolb, 1984) and managing stress (Shoulders, Whitehead, & Morrison, 2018). By understanding how students’ progress through a semester in terms of both their learning and their management of stress, instructors and academic advisors can better anticipate times …

Employee Engagement As A Shared Responsibility: A Study Of Engagement Strategies Employed By Legal Assistants, Thomas A. Steele

Graduate Theses and Dissertations

The purpose of this study was to identify strategies used by legal assistants to engage, stay engaged, and reengage, when appropriate, in their work, in particular when common organizational efforts fall short or do not exist. Constructivism and job demands-resources (JD-R) were the primary frameworks for understanding and analyzing the phenomenon of developing engagement strategies.

Qualitative data were drawn through semi-structured interviews with 16 legal assistants. The interviews were recorded and transcribed. Trustworthiness and validity were enhanced by using multiple respondents and allowing each to review the transcripts for accuracy, fairness, and clarity. The transcriptions were then analyzed for themes. …

Examining Pathogenesis And Preventatives In Spontaneous And Staphylococcus-Induced Bacterial Chondronecrosis With Osteomyelitis In Broilers, Nnamdi Simon Ekesi

Graduate Theses and Dissertations

Bacterial chondronecrosis with osteomyelitis is the most important cause of lameness in broilers. This is important to poultry production, as it poses animal welfare issues, and causes a significant loss in revenue. The remediation of this disease requires the study of its etiology with fitting models and evaluating preventatives. The research reported herein covers genomic virulence analysis of BCO isolates, mainly Staphylococcus aureus, and Escherichia coli retrieved from lame birds. We found that S. aureus isolates were closest to chicken strains in Europe but may have been in the Arkansas area for a decade. Phylogenomics suggest our S. aureus is …

The Effects Of Multiple Stressors On Stream Communities: The Convergence Of Drought, Nutrient Pollution, And Invasive Species, Robert Joseph Fournier Iii

Graduate Theses and Dissertations

Freshwater systems experience multi-faceted degradation from a variety of ecological and environmental stressors. Three common stressors in these systems, drought, nutrient pollution, and invasive species, have wide-ranging effects on stream population- community- and ecosystem dynamics. We have a broad understanding of how each of these stressors works to influence stream systems independently. However, we still know relatively little about if, and how, these stressors might interact when they co-occur. Though drought is a natural part of many stream systems, all three of these stressors can be exacerbated or facilitated by anthropogenic actions. Accordingly, as human population and resource use continue …

Dietary Regulation Of Successful Aging, Aubree L. Hawley

Graduate Theses and Dissertations

The current growth of the older population is unprecedented in U.S. history. Chronic disease and functional limitation commonly develop prior to old age, leading to prolonged physical disability and decreased well-being. The development of chronic disease and loss of independence is associated with lean body mass (LBM) loss and fat mass gain beginning in middle age. Therefore, it is important to identify modifiable factors to mitigate deleterious shifts in body composition to promote successful aging (SA). The concept of SA is associated with longevity, the absence of disease and disability, and subjective components of well-being, however, an operational definition has …

The Use Of Social Media In English Teaching And Learning: Exploring The Perceptions And Experiences Of English As A Foreign Language Instructors, Waheeb Shadid Albiladi

Graduate Theses and Dissertations

The attention on using social media for educational purposes is increasing. Research shows that social media platforms are effective teaching and learning tools. The purpose of this study was to examine foreign language teachers’ experiences in using social media in the teaching and learning of English. Research Design: A qualitative research method was used for the data collection and analysis. Data were collected through a survey and in-depth interviews with foreign language teachers. The participants included 35 English teachers (15 for the interview, 35 for the survey) representing different educational levels, including public and private schools and foreign language institutions. …

Growth And Characterization Of Semiconductor Materials And Devices For Extreme Environments Applications, Abbas Sabbar

Graduate Theses and Dissertations

Numerous industries require electronics to operate reliably in harsh environments, such as extreme high temperatures (HTs), low temperature (LT), radiation rich environments, multi-extreme, etc. This dissertation is focused on two harsh environments: HT and multi-extreme.

The first study is on HT optoelectronics for future high-density power module applications. In the power modules design, galvanic isolation is required to pass through the gate control signal, reject the transient noise, and break the ground loops. The optocoupler, which consists of a lighting emitting diode (LED) and photodetector (PD), is commonly used as the solution of galvanic isolation at room temperatures. There is …

Effects Of Gatekeeper Course Modality, Age, Gender And High School Gpa On Kaplan Subject Area Exam Scores, Vernon Hoffman

Graduate Theses and Dissertations

The question of equivalency regarding course modality has plagued and intrigued educators for as long as multiple modalities have existed. In the modern world of academia, the two prevailing modalities are face-to-face or traditional courses and online courses. A multitude of factors have contributed to the increase in online course offerings, including increasingly dependable technology and fiscal pressures on institutions of higher learning.

A great deal of scholarly research has compared modalities using within-course measures such as course grades and comprehensive final exams. Most of these studies have found the two modalities equivalent. However, a dearth of research exists which …

The Surveillance Of Gastrointestinal Parasitic Nematodes Of Northwest Arkansas Dairy Cattle Using Traditional And Genetic Parasitological Identification Procedures, Eva M. Wray

Graduate Theses and Dissertations

Traditional and genetic parasitological identification procedures were compared using naturaland artificial nematode parasite infections in Holstein steer calves. The traditional parasitological procedures measured fecal egg counts, coprocultures with subsequent larval collection and adult nematodes collected at necropsy. The genetic identification procedures measured ITS-2 sequences extracted from different stages of nematode development: raw feces, concentrated nematode eggs, third stage larvae and adults. The primary nematodes observed were Cooperia oncophora, Cooperia punctata and Ostertagia ostertagi. The traditional techniques were not significantly different from one another, while the genetic sequencing showed variation amongst the different procedures. The raw feces sequences showed the most …

Investigating The Potential Of Microbial Metabolites And Mtor Signaling On Chicken Necrotic Enteritis, Mohit Bansal

Graduate Theses and Dissertations

Necrotic enteritis (NE), caused by C. perfringens and coccidiosis, is responsible for substantial economic loss annually. In the first chapter, we investigated the effect of secondary bile acid on necrotic enteritis. Day-old broiler chicks were randomly assigned to 5 groups of diets supplemented with 0 (basal diet), 0.8, 1.0, and 1.5 g/kg (on top of basal diet) deoxycholic acid (DCA). The birds were challenged with Eimeria maxima (20,000 oocysts/bird) at d 18 and C. perfringens (109CFU/bird/day) at d 23 and d 24 to induce NE. Birds were sacrificed at d 26, and ileal tissue and digesta samples were collected. DCA …

Understanding Radiation Resistance In Head And Neck Tumor Xenografts Using Diffuse Reflectance And Raman Spectroscopy, Sina Dadgar

Graduate Theses and Dissertations

Each year, 800,000 new patients are diagnosed with head and neck squamous cell carcinoma (HNSCC), a majority of whom are treated with a combination of daily fractions of radiation and weekly chemotherapy sessions for up to seven weeks. Current methods to evaluate treatment response of individual patients are limited to anatomical measurements of tumor burden using CT scan or MRI 4-8 weeks after completion of treatment. However, earlier knowledge of radiation-response prior to or at early days after commencement of therapy can aid oncologist with escalating and de-escalating treatment plans for exceptionally non-responding and responding patients. Such a knowledge can …

Effects Of Commercial Feed Additives On Growth Performance And Gut Microbiota Of Nursery Pigs, Xiaoyuan Wei

Graduate Theses and Dissertations

To secure animal welfare and maximum production, feed additives are often added to nursery pig diets to increase nutrition digestibility, enhance intestinal health, and prevent or mitigate disease, with the ultimate goal of improving growth performance. This thesis performed a longitudinal analysis using next-generation sequencing to investigate the dynamic changes of gut microbiota in weaned pigs fed commercial feed additives. Chapter II was used to evaluate the effects of organic acid mixture on growth performance and gut microbiota of weaning pigs. This study demonstrated that the inclusion of 0.035% (SBA0.035) or 0.070% (SBA0.070) sodium butyrate in a diet containing 0.5% …

Neogene And Quaternary Events Shaped Diversification And Speciation In Bhutanese Rheophilic Fishes Of The Family Nemacheilidae (Cypriniformes) And Sisoridae (Siluriformes), Karma Wangchuk

Graduate Theses and Dissertations

Biogeography of the Himalayan region [to include the Qinghai-Tibetan Plateau (QTP)] evolved over a ~30M year span, catalyzed by the collision of the Indian and Eurasian plates. The resulting uplift produced major ecological and climatic effects, that in turn drove the diversification of biodiversity. As a result, the QTP is designated as a global biodiversity hotspot particularly vulnerable to cumulative climatic effects, including shrinking distributions, declining numbers, and local extinctions. Understanding how the biodiversity within the Himalaya/ QTP was established and maintained is a necessary first step in prioritizing conservation efforts.

Fishes in global montane regions, such as the Himalaya, …