TAMU-CC Repository
The Texas A&M University‐Corpus Christi (TAMU‐CC) repository is an open online site for storing and sharing digital content created or owned by the TAMU‐CC community. Content includes published and unpublished research and scholarship as well as archival materials. The service is managed by the Mary and Jeff Bell Library in cooperation with the Texas Digital Library. Learn more
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Recent Submissions
Characterization of the relationship between nitric oxide and serotonin in the formation of long-term memory in an invertebrate model
(2024-05-03) Richards, Landrue C.; Mozzachiodi, Riccardo; Cammarata, Kirk; Omoruyi, Felix
Learning is a process by which all animals modify their behaviors to ensure increased fitness. In the mollusk Aplysia, long-term sensitization (LTS) serves as a prime example of this learning process, where defensive behaviors, such as the tail-siphon withdrawal reflex (TSWR), are heightened for prolonged periods as a result of repeated exposure to noxious stimuli, showcasing the organism's adaptation to experience. This behavioral plasticity is paralleled by neurophysiological changes, including the long-term increase in excitability (LTIE) of tail sensory neurons (TSNs), serving as neural correlates of LTS and providing a window into the cellular and molecular mechanisms sustaining this form of memory. The neurotransmitter serotonin (5-HT) is known to mediate LTS formation in Aplysia. 5-HT exposure alone can also induce LTS in vivo as well as LTIE in vitro. However, recent findings indicate that the neurotransmitter nitric oxide (NO) is also necessary for LTS formation. However, it is not known where exactly NO lies in the chemical pathway concerning 5-HT. Therefore, the purpose of this project was to investigate NO’s involvement in long-term memory formation in an invertebrate model. More specifically, the way two chemical messengers, NO and 5-HT, work in the brain. Our findings reveal that NO likely functions downstream of 5-HT, as evidenced by the blockage of in vivo LTS formation by L-NAME, an NO inhibitor, despite the presence of 5-HT. Further, we confirm that NO's role is not significant in in vitro long-term increase in excitability (LTIE), reinforcing its specific importance in LTS. In conclusion, our study significantly advances the understanding of LTS in Aplysia by detailing the interactions between NO and 5-HT. Our findings not only advance our understanding of LTS but also open new avenues for memory and learning research, emphasizing the complexity of neurochemical interactions in learning processes.
Metadiscourse markers in L2 source-based informative essays: An analysis of texts written by L2 undergraduate students
(2024-04-22) Pham, Dang Thuy Anh; Doolan, Stephen M; Andrews, Christopher; Pina, Manuel
Improving writing skills is considered essential for L2 students, especially in academic settings, reflecting part of the overall language proficiency (Teng et al., 2022). L2 writing complexity, influenced by internal and external factors, inspires the use of metadiscourse markers as valuable tools for self-reflection and communication (Casanave, 2017; Teng & Zhang, 2018; Hyland, 2004). Prior research has explored metadiscourse markers in L1 writing, contributing to proficiency improvements (Aull, 2019; Hong & Cao, 2014; Yoon, 2021; Lee & Deakin, 2016), within college students’ writing (Bax et al., 2019; Huh & Lee, 2016; Ramoroka, 2017), graduate theses and dissertations (Hussein et al., 2018; Ozdemir & Longo, 2014), and research articles and book reviews (Abdi, 2011; Gillaerts & Van de Velde, 2010). However, there is a limited examination of how these markers function in L2 college students’ source-based type of writing. This study, based on Hyland’s framework (2005), analyzes data from L2 college students’ informative source-based writing. Particularly, I will look at a total of 36 L2 informative, source-based, First-year writing program essays, with 16 essays in the higher-rated category (5258 words) and 20 essays in the lower-rated category (5169 words), collected from L2 students within the First-year Composition programs from two universities in the US. The essays were analyzed by a computerized program to produce comprehensive concordance lists of markers alongside essential information about the prompts and the authors, enabling analyses to explore the diversity distribution and specific functions that metadiscourse markers serve in these essays. The findings reveal that higher-rated essays displayed a broader spectrum of metadiscourse features, fostering connections within essays and enhancing communication with readers. Furthermore, while engagement markers, particularly imperative directive features, were preferred by students from both proficiency groups to establish a direct relationship with readers, various subtypes of hedges and boosters also stand out, especially in a higher-rated group, as productive tools for expressing specific shades of certainty and commitment. Lastly, highly frequent usage of self-mentions in lower-rated essays can signal students’ preference towards expressing ideas from personal perspectives and possible struggles in critically synthesizing source texts into statements. In summary, understanding metadiscourse markers used in L2 writing helps students with tools to enhance writing communication, provide insights for teachers in improving teaching approaches, and inspire further scholarly discourse.
Group consensus with the Analytical Hierarchy Process using singular value decomposition and methods for tensors
(2024-05-03) Nava, Rebecca Lee Ann; Tintera, George; Vasilyeva, Maria; Mallikarjunaiah, S. M.
The Analytical Hierarchy Process (AHP), created by Saaty [12, 13, 15, 14], has been used over the last few decades to enhance the decision making process in several fields of study. Such fields include medicine, computer science, education, and business. AHP uses pairwise comparison matrices (PCM), where the diagonal entries 𝑎𝑖𝑖 = 1 and for all other entries 𝑎𝑖𝑗, 𝑎𝑗𝑖 = 1/𝑎𝑖𝑗. Consistent pairwise matrices will satisfy the requirements of a PCM, and will also satisfy the consistent property of 𝑎𝑖𝑘 = 𝑎𝑖𝑗 ×𝑎𝑗𝑘. Pairwise comparison matrices that are inconsistent may not necessarily be of rank one and will not satisfy the consistent property. Any inconsistent PCM will have an approximate consistent version. Solving a PCM means determining the individual weights of the criteria. Saaty’s Eigenvector method can be used on consistent PCMs to determine the weight vector, but is unreliable for those that are inconsistent. Gass and Rapscak [10] proposed a new method of determining weights through SVD, which is applicable to pairwise comparison matrices of varying consistency. This thesis will focus on creating tensors from pairwise comparison matrices. The tensor slices or faces will each be a pairwise comparison matrix. Each slice can be compared to an individual’s relative preference, and the tensor will group all preferences together. Ideally, the individuals will be making a decision on the same topic, but their ”best” choice may not be the same as the other group members. Once the preferences are grouped together, the method of unfolding will be used to further study the tensor. Saaty’s geometric mean method for group consensus will also be observed and compared to the method of unfolding. There are conditions a method must meet to be used for determining group consensus. These conditions will be observed and proven for unfolding. Afterwards, some calculations will be made to compare the methods and understand their differences.
Diffusive transport and coral calcification: A comparative study of branching and plating morphologies under ocean acidification
(2024-05-03) Herrera, Bryanna Noelle; Bahr, Keisha D.; Bogucki, Darek; Hu, Xinping
Corals are sessile animals that are subject to their environment and have various colony morphologies that influence their diffusive boundary layer, a thin layer of fluid surrounding the coral surface. Boundary layer dynamics are crucial for corals to acquire nutrients from the environment, supporting essential functions like calcification. However, we lack knowledge regarding individual and species-specific responses to changes in water column conditions and how these changes can affect boundary layer dynamics and, consequently, calcification. Therefore, the purpose of this study is to incorporate engineering concepts to investigate drivers and connections between the physical and chemical controls on coral calcification in current and future predicted ocean acidification (OA) conditions. The Hawaiian rice coral, Montipora capitata, is a polymorphic coral with multiple growth forms, including branching, plating, and encrusting. Six branching and plating M. capitata colonies were collected, and three of each morphology were exposed to two different water chemistry conditions for two weeks. Microsensor profiles were conducted to measure boundary layer thickness and water chemistry changes, and a flume was designed and constructed to control water flow. The findings show that the plating morphology has a thicker boundary layer than the branching morphology at the site of primary photosynthesis. Moreover, at the site of primary photosynthesis, a significant difference in surface oxygen (O2) concentrations was observed between the two morphologies in ambient conditions, implying increased O2 efflux rates and coral productivity from a branching morphology.
No humans here: Exploration in the digital age
(2024-05-01) Grabko III, John L.; O'Malley, Ryan; Rote, Carey; Pena, Joe; Durham, Jonathan
No Humans Here connects a lineage between landscape painters of the Hudson River School and Impressionists with 3D landscape renderings from artists of the early digital age at the turn of the millennium – work that conveyed an era of unbound creativity before dwindling as populated by more and more people over time. This transition diluted elements of exploration and curiosity through actions of curation, control, and exploitation - to the point that what once was, no longer remains. The initial magic, mystery and creativity of those early explorers and inhabitants in this digital age are now merely artifacts. As global exploration began to reach its limits by the mid 20th century, the advent of digital space opened new lands to cultivate and explore. Artists of the 90’s began using modeling programs, beginning with natural landscapes and architecture as a launchpad for creativity, akin to previous eras of landscape art – with particular comparisons to the Hudson River School. These early digital worlds were void of human inhabitants due to the practical nature of digital space itself – that humans do not exist directly within, rather we (currently) interact externally – or their presence is only alluded to because of technical limitations. Unlike early American landscape paintings, users of this new medium were unconstrained by romanticized realism or religious fervor, rather, they were unbound by the vastness of their own imaginations, and fantasy and science fiction literary influences of the 20th century such as J.R.R Tolkien (1892-1973) and William Gibson (b. 1948). Additionally, the use of light, color, and visual-distortion brushstrokes of Impressionist landscape painting parallels the pixelated, low-resolution imagery of the early digital age. As of this writing, humans do not physically exist within digital space but use it as a gateway for mental projection. Digital space exists outside of time itself – records of its early history still live on online, untouched and without decay, while also constantly evolving through the present. No Humans here pays homages to the creativity of early 90's digital landscapes through nostalgia and reimagining, while also questioning hope, loss, and entropy of our digital futures.