UARK (University of Arkansas )
Not a member yet
19829 research outputs found
Sort by
Insights From Automated Mineralogic Analysis of Modern Sand
Get PDFMethods for determining and categorizing the modal compositions of sand and sandstone have long been a subject of debate in the field of sedimentary geology. Point counting is the most commonly used technique for determining modal compositions from petrographic slides, which are then categorized based on relative proportions of quartz, feldspar, and rock (or lithic) fragments. However, this approach fails to adequately preserve relevant textural data, such as grain size and sorting, which play an important role in diagenesis and in influencing reservoir quality. Additionally, the categorical nature of point counting results in a lack of specificity and loss of valuable data regarding intra-grain mineral proportions, which could be important for provenance analysis.
The Tescan Integrated Mineral Analyzer (TIMA) can address some of the deficiencies associated with traditional point counting by providing discrete mineral maps of individual grains within a sample. TIMA is a fully automated analysis, during which a scanning microscope utilizes backscattered electron (BDE) and energy dispersive X-ray (EDX) technology to determine the precise elemental makeup of a sample. This information may then be used to infer mineralogy at micron resolutions.
This study explored the insights gained from TIMA data for determining the grain size and modal composition of seven modern sand samples with a diverse suite of compositions and textures. The purpose of this work was to develop a quantitative approach to analyzing the composition and morphology of clastic sediment to provide more insight than point counting alone in hopes of providing value to future provenance studies. A combination of ImageJ and Python scripts was used to analyze the mineralogic composition and morphology of individual grains and the distribution and compositions of each grain size within a given sample. I applied nonmetric multidimensional scaling using two dissimilarity metrics to evaluate inter-grain mineral relationships within a sample. I then assessed the quality of the fit of these solutions and suggested several explanations for suboptimal model performance. Additionally, I performed principal component analysis as an alternative method to evaluate inter-grain mineral relationships and evaluated the effectiveness of that approach. I found that, though conventional metrics suggest a poor fit, meaningful relationships could be drawn from multidimensional scaling analysis. I also concluded that principal component analysis may be a better choice for visualizing and interpreting intra-grain mineral relationships. Finally, I found that morphological analysis is both possible and insightful with TIMA data. Ultimately, this work serves as a notable step toward leveraging TIMA data for provenance analysis of sand(stone) composition
A Wicked Game
Get PDFA Wicked Game is an installation comprised of a video game in an arcade cabinet, photographs, sound, and sculpture. The installation explores the complexity of play and personal memory. Working from the concept of “wicked” (Epstein) learning environments – domains with hidden rules, unstable structures, and inconsistent feedback – the project constructs a playable space, where players must navigate an inhospitable environment, echoing the experience of living in a world that resists accommodation.
The installation centers around an all-black arcade cabinet placed in a darkened gallery space, inviting visitors to play A Wicked Game. The game demands the player know things which are never taught, demands that they contort themselves to a constantly changing control scheme, and success requires mastery combined with luck. The narrator is deliberately inhospitable. The game’s mechanics disorient and confuse, both repelling and enticing the player.
Other works in the exhibition reinforce themes of loss, memory, and uncertainty. Personal storytelling is interwoven with scholarly discourse and design research, positioning the work as both autobiographical and theoretical.
A Wicked Game traverses an artistic practice informed by game logic, resisting clarity and embracing complexity. It invites players to reflect on what it means to inhabit systems that are unstable, arbitrary, and often unjust to imagine new forms of cooperative play and shared empathy
The Efficacy of Foam-Based Hand Sanitizers for the Control of Enveloped and Non-enveloped Virus Transmission
Get PDFInfectious disease transmission due to viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza virus, human noroviruses (HuNoV), and hepatitis A, can occur via person-to-person contact or contaminated surfaces. Effective hand hygiene, including hand washing and use of hand sanitizers, is considered a critical tool for the control of infectious disease transmission, as recommended by the United States Centers for Disease Control and Prevention and the World Health Organization. However, while research on hand washing efficacy is well-documented, research on hand sanitizer efficacy, particularly for foam-based products, remains limited. This research addressed critical gaps in the area of hand sanitizer efficacy, particularly with foam-based hand sanitizers which are widely used but generally underexplored. First, the recovery of bacteriophage phi6 (Φ6; a surrogate for enveloped viruses such as SARS-CoV-2) from the whole hands was optimized. Φ6 was applied on either the palmar surface or the whole hand, recovered based on wet or dry conditions using three eluents [lysogeny broth (LC), tryptic soy broth (TSB), and 1.5% beef extract (BE)] and three recovery methods [glove juice method (GJM), hand rinsing, and modified dish method]. Recovery methods, inoculum application type, and recovery basis significantly impacted Φ6 recovery. Study results revealed that GJM and dry basis recovery are not ideal for Φ6, however, to maximize Φ6f recovery from the hands, inoculum should be applied to the palmar surface and recovered using LC medium while the inoculum is still wet. The study also examined the in vitro efficacy of foam hand sanitizers against enveloped and non-enveloped viruses. The efficacy of one non-alcohol-based hand sanitizer (NABHS) and four alcohol-based hand sanitizers (ABHS) with benzalkonium chloride (BZK) and ethanol as active ingredients, respectively, were explored using Φ6 as a surrogate for enveloped viruses and bacteriophage MS2 (Emesvirus zinderi) and Tulane virus (TuV) as surrogates for non-enveloped viruses (e.g., HuNoV and hepatitis A) with an exposure time of 10 s. While Φ6 was completely inactivated (5.23 ± 1.64 log reduction), MS2 proved resistant to inactivation (0.04 ± 0.08 log reduction). Conversely, efficacy against TuV significantly varied across products, indicating that while 10 s may be sufficient to inactivate enveloped viruses, higher exposure time may be necessary to achieve similar log reductions against non-enveloped viruses such as human norovirus based on the tested surrogates. Finally, the in vivo efficacy of commercially available ABHS and NABHS against enveloped and non-enveloped viruses was evaluated, assessing varying dosing volumes and rubbing time. The findings revealed that the efficacy of the products is significantly affected by virus type, rubbing time, and overall formulation. Employing Φ6 as a surrogate for enveloped viruses yielded a significantly higher log reduction (2.83 ± 1.98) than MS2, the surrogate utilized for non-enveloped viruses (0.50 ± 0.53). Furthermore, when hands were rubbed until dry following hand sanitizer application, a significantly higher log reduction (2.69 ± 2.06) was observed compared to 10 s rubbing time (0.65 ± 0.75), which is typical among users
What\u27s Love Got To Do With It? A Content Analysis of Romantic Depictions in Tween Television Programming
Get PDFIn the streaming era of entertainment, television programming is available at the touch of a fingertip to any pre-adolescent tween (those between the ages of 8-13) with a smartphone. Previous content analyses have examined romantic relationship content on television programming in a limited manner, covering mostly teen shows and sexual behavior, rather than tween shows and romantic relationship behavior. And so, despite the fact that tweens tend to use media as a socializing agent for learning acceptable romantic relationship norms, not much is known about how television programs likely watched by this age demographic are depicting romantic relationships. Therefore, it is crucial to learn more about what is being depicted to understand if the romantic relationship norms pre- and early adolescents might be learning from these depictions are healthy or unhealthy in nature. Based on television ratings (TV-PG and TV-14) and Common Sense Media’s age recommendation tool, a population of 11 television programs consisting of 326 episodes was identified, and 177 episodes were coded as a sample. The results indicated that there was a high amount of healthy romantic relationship language and behaviors depicted, including instances of flirting (both verbal and nonverbal), affectionate interpersonal touching, talk about liking or loving a person romantically, talk about building or maintaining a romantic relationship, and talk about romance in general. Other behaviors, such as kissing, were present less frequently and were often more present in television shows rated TV-14 as opposed to TV-PG. Romantic relationship language and behavior, both healthy and unhealthy, were more likely to appear in shows rated TV-14 as opposed to TV-PG. This content analysis provides evidence that romantic relationship language and behaviors are depicted in television shows likely consumed by tweens for those who want to study the context of these depictions further
Development of Si-Based Germanium-tin Infrared Photodiode
Get PDFShort-wave infrared (SWIR) and mid-wave infrared (MWIR) photodetectors have attracted increasing attention for the past few decades. SWIR and MWIR detectors are used for a wide range of applications in military and civilian defense, such as future automotive night vision, video surveillance security cameras, and integrated night vision in mobile/wearable electronics. The current market-dominating IR photodetector technology is mainly developed with the costly III-V or II-V material systems, such as InGaAs, InSb, and HgCdTe. While many efforts have been made towards the hybrid integration of III-Vs or II-VIs on a Si substrate, it is highly desirable to develop an alternative material featuring lower-cost and high-performance for photodetectors covering broad IR wavelength range.
Recent study of all-group-IV alloy SiGeSn opens a new venue for Si-based optoelectronics. SiGeSn offers: (1) The ability to independently engineer the lattice constant and bandgap by appropriately selecting the compositions of Si, Ge, and Sn; (2) The ability to achieve true direct bandgap material by incorporating a few percent Sn; (3) The possibility of forming desirable type-I band alignment to provide a favorable quantum confinement for the design of optoelectronics; (4) The IR wavelength coverage up to 12 μm through band-to-band transitions and all wavelengths beyond 12 μm through intersubband transitions; (5) The compatibility with CMOS processes with a low growth temperature (below 400 oC). The key enabling factors for SiGeSn over all current IR technologies also include significantly lower radiative and Auger recombination (10-28~10-29 cm6 /s) coefficients for longer carrier lifetime (\u3e100 μs), and larger oscillator strength for higher absorption coefficient (\u3e104/cm), giving a shorter carrier extraction time, lower dark current, and higher internal quantum efficiency. My dissertation shows the development of general GeSn device fabrication processes, which were later employed in the fabrication of GeSn laser and detector devices. This successfully demonstrated the first electrically injected GeSn laser and avalanche photodiode, which showed clear punch-through and avalanche breakdown behavior.
Further, investigations into Ion implantation of arsenic (n-type) and boron (p-type) in GeSn (~10% Sn) is feasible but induces lattice damage. Higher doses and energies cause crystal disorder up to amorphization, partially healed by low-temperature rapid thermal annealing. Annealing at 300°C recovers some damage, while 400°C significantly restores crystallinity for Sn ≤11%. SIMS confirms impurity incorporation, and post-implant annealing activates p–n junctions. A fabricated GeSn diode with implanted regions exhibits rectifying I–V behavior and infrared photo response.
This work advances monolithic GeSn-based avalanche photodiodes (APDs) on silicon, enabling extended infrared detection and CMOS compatibility. A SACM structure with a GeSn absorber, Si multiplication layer, and Ge buffer enhances carrier transport, achieving a broad spectral response beyond 2.1 μm at room temperature. The GeSn-on-Si APDs show clear punch-through and avalanche breakdown. Internal gain is evident, with multiplication factors of ~1.4 at 250 K and ~4–4.5 at 77 K.
These findings highlight GeSn\u27s potential for extending silicon photonics into the infrared. GeSn APDs on Si achieve spectral response beyond Si and Ge bandgaps, with avalanche gain in the 1.5–2.0 μm range. CMOS-compatible ion implantation and low-temperature annealing enable GeSn integration into standard silicon processes, paving the way for monolithic, CMOS-compatible infrared photodetectors and optoelectronic devices in the SWIR/MWIR regimes
Indigenous Materials Characterization for Additive Construction Applications
No full textAdvantages of concrete additive construction (AC) include the ability to print an object at the point of need with less waste, the geometric flexibility for novel shapes, and the reduction in the amount of hard physical labor required by construction workers. To date, most AC structures are designed and built using select high-quality materials, however, the implementation of indigenous, locally sourced soils and aggregates has started to grow as a feasible alternative, especially in remote locations in which the acquisition of conventional or select materials is unattainable. The potential to use indigenous materials reduces the logistical burdens associated with most concrete construction, and it improves the sustainability aspects, making the technology even more attractive.
To evaluate the suitability of indigenous materials sourced on-site to create AC concrete mixes, a full suite of characterization tests was conducted on a variety of indigenous materials sourced from around the world. The properties of the materials were determined, and then concrete mixes were evaluated to better understand the influence of various properties on the printability and strength of the AC concrete. Printability in this study refers to the pumpability and buildability of a mix, meaning the fresh material could be pumped through a progressive cavity pump, and then extruded beads could be stacked consecutively without excessive slump or collapse. The selection of the appropriate set of tests for a future testing protocol was guided by the most influential soil characteristics for AC concrete mix performance: the fines content, plasticity, gradation, and specific gravity in conjunction with absorption. These properties provided the relevant information needed to assess the suitability of indigenous materials for AC concrete mixes and identify cases when further processing is required in the field.
The amount of fines present was shown to influence workability and the water demand, and higher fines contents tended to improve the pumpability and buildability of a mix. The plasticity of the indigenous soils also strongly influenced the fresh and hardened properties of AC concrete mixes. Increased plasticity enhanced the pumpability and buildability of mixes; however, these mixes tended to have higher shrinkage cracking and lower strength. The gradation of indigenous materials provided information regarding maximum particle size and the coarseness of an aggregate, delimiting AC equipment and printing parameters. Gradation also likely helps identify the potential for a mix to pack within the rotor-stator; however, more research is needed to confirm the observations in this study. Specific gravity and absorption are important properties in the mix design proportions and having these values can help precisely control total water demand to ensure pumpability, avoid segregation, and enhance adhesion between layers.
The Methylene Blue Value (MBV) test was proposed as a field-applicable test method to determine the clay content of soils. MBV presented challenges regarding the variation of results from each soil analyzed. MBV denoted a directly proportioned linear function with clay content values, however, each soil analyzed resulted in a unique range of MBV. Because of this, the MBV was not able to uniquely identify the clay content or plasticity of a given indigenous soil
Implications of Acetylation and Phosphorylation on Metabolic Enzymes
Get PDFAll living things depend on glycolysis and the TCA cycle for energy production and metabolic control. Post-translational modifications (PTMs) such as acetylation and phosphorylation, which can change enzyme activity, substrate binding, and overall metabolic balance, tightly regulate these pathways. Diseases like cancer and metabolic problems are associated with disruptions in these alterations.
Serine phosphorylation and lysine acetylation are two of the many PTMs that are evolutionarily conserved processes that alter protein function. Previously thought to be a static histone alteration, acetylation is now understood to be a dynamic regulator of metabolic enzymes that modifies contacts, charge, and conformation. In response to biological signals, phosphorylation, a well-known signaling switch, precisely regulates the activity of enzymes. Nevertheless, little is known about the functional effects of site-specific PTMs on metabolic enzymes, specifically how they affect catalytic efficiency, allosteric regulation, and the development of disease. Due to their incapacity to replicate steric or electrostatic disturbances, conventional methods like mutagenesis frequently fall short in reproducing PTM effects. Innovative techniques such as genetic code expansion (GCE) have been developed to address this, allowing for the site-specific inclusion of phosphoserine or acetyllysine through stop codon suppression. This method makes use of pyrrolysyl-tRNA synthetase/tRNA pairs to precisely examine the structural and functional effects of acetylation in vivo. In this research, I used a multidisciplinary method that combines comparative genomics, enzymology, and GCE to analyze how phosphorylation and acetylation rewire the activity of three key enzymes: phosphofructokinase (Pfk), glucokinase (GK), and isocitrate dehydrogenase (IDH). I clarify how site-specific changes affect enzyme kinetics, substrate binding, and metabolic flux by investigating phosphorylation in cancer metabolism using human epithelial cell lines and E. coli as a model for prokaryotic PTM control
Examining the Combination of Race-by-Age Segregation on Violence in Little Rock, Arkansas
Get PDFThe Present study addresses the issue of residential segregation. Specifically, how the physical isolation of populations segregated based on both age and race affects violent crime. The sample includes all 155 Census block groups, which represent neighborhoods, in the city of Little Rock Arkansas. Data is accessed from the U.S. Census and the Little Rock Police Department. The current study asks: does the segregation of juveniles by age and race affect the distribution of crime? The theoretical frameworks guiding this research are social disorganization theory, structural-cultural theories of crime, the racialization of space perspective, and routine activities theory. The key findings are as follows. First, violence is moderate-to-high, but skewed to the high end of the distribution such that a few block groups have exceptionally high rates of crime. Second, Little Rock as a whole, also has a high degree of racial segregation. Third, regarding the control variables, the average Little Rock neighborhood contains considerable disadvantage. Fourth, the results of all three OLS models show that segregation strongly predicts increased violent crime rates. Finally, across all three models, disadvantage has a statistically significant positive association with crime
Blackberry Plant Named ‘A-2718T’
Get PDFDescription and specifications of a new and distinct blackberry cultivar named ‘A-2718T’ which originated from seed produced by a hand-pollinated cross ‘A-2487T’ (a non-patented, unreleased genotype) × ‘A-2418T’ (a non-patented, unreleased genotype). This new blackberry cultivar can be distinguished by its medium to large fruit size, firm berries, excellent crop, late season ripening, and good plant health
End Times: American Mortality, Death Materiality, and Social Death in the 1990s
No full textThe United States in the 1990s was marked by pervasive representations of death in popular culture. As death imagery became increasingly visible in entertainment, there was a growing detachment from the embodied, biological realities of death, a tension intensified by the ongoing AIDS crisis. This project explores how death is politicized and how decisions about who lives and dies are shaped by power. I draw on a constellation of theoretical frameworks that collectively illuminate the operations of state-sanctioned death and social abandonment. These include Michel Foucault’s concept of biopolitics, which examines the management of life by state power; Giorgio Agamben’s focus on the production of the corpse as a byproduct of sovereign authority; and Achille Mbembe’s formulation of necropolitics, which extends biopolitical analysis into the realm of war and racialized violence. I also incorporate insights from queer theory, critical race theory, and death studies to trace how marginalized identities are targeted for physical and social death. The project begins with readings of Toni Morrison’s Beloved and Don DeLillo’s White Noise, which establish foundational associations between death and the American cultural psyche leading into the 1990s. I then analyze the political use of the corpse in AIDS activism, focusing on ACT UP and DIVA TV’s documentation of protest funerals. Following this, I examine Jonathan Larson’s Rent and Tony Kushner’s Angels in America: A Gay Fantasia on National Themes to explore the tensions between capitalism and what I term queer (pro)creation--an ethos of community care, legacy-building, and artistic protest. Finally, I turn to Tananarive Due’s The Between and Stephen King’s The Green Mile to consider the material and liminal dimensions of racialized death, particularly as manifested in modern-day lynching and state executions