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    Freeze-Disturbance effects on biomass allocation in expansion of Black Mangrove (Avicennia Germinans) along a latitudinal gradient in Texas
    (2023-08) Portmann, Maxwell D.; Proffitt, Charles E.; Devlin, Donna J.; Daru, Barnabas H.; Battaglia, Loretta L.
    In response to warming minimum temperatures, Avicennia germinans is encroaching poleward on the Texas Gulf Coast (TGC) into saline marshes dominated by Spartina alterniflora and Batis maritima. Increased Avicennia cover provides greater protection from soil subsidence and shoreline retreat. However, intense freeze disturbances cause widespread mangrove mortality reversing succession, and increasing the risk of soil subsidence and shoreline retreat due to the loss of below-ground biomass. We conducted a “natural experiment of opportunity” to measure below- and above-ground biomass allocation in Avicennia recovering from catastrophic disturbance caused by the 2021 Winter Storm Uri at sites along a freeze-disturbance gradient across the South and Central TGC. Port O’Connor (28.46°N) was the most severely affected site, Cohn Preserve on Mustang Island (27.71°N) was moderately affected, and Laguna Atascosa National Wildlife Refuge (26.35°N) was minimally affected (min. temp. °C ~ -9.0, ~ -7.4, ~ -5.5 respectively). A second freeze event occurred in December 2022 that severely affected Port O’Connor and moderately affected Cohn Preserve (min. temp. °C ~ -6.6, ~ -5.8 respectively). In an additional methods experiment, we quantified differences in root productivity in in-growth cores containing either peat moss or local substrate at each site. Multiple root ingrowth cores were inserted near the canopy edge of isolated Avicennia shrubs (n=6; 5 at Port O’Connor) at the three sites and collected at 4-month intervals (total cores = 102). Root productivity (g * (m-2 day1)) assessed in a one-way ANOVA and Tukey multiple comparisons, increased with increasing freeze-disturbance effects (F2,28 = 6.386, p<0.01, Port O’Connor: mean = 0.192, sd = 0.188, Cohn Preserve: mean = 0.065, sd = 0.081, Laguna Atascosa: mean = 0.047, sd = 0.089). Using the below-and above-ground relative growth rates to assess the root:shoot biomass allocation ratio, we found an increasing ratio (greater roots to shoots) with increased freeze disturbance (one-way ANOVA and Tukey HSD tests, F2,12 = 6.049, p<0.05, Port O’Connor: mean = 0.191, sd = 0.118, Cohn Preserve: mean = 0.061, sd = 0.066, Laguna Atascosa: mean = 0.015, sd = 0.01). Further, we found no clear trend in quantity or variability in root productivity between native and peat moss substrate types in root ingrowth cores for root biomass at any site (F2, 53 = 0.021, p=0.8). However, peat moss ingrowth cores did consistently have less root necromass after the Dec. 2022 freeze suggesting better survival or lower turnover. Peat moss ingrowth cores contained lower quantities of live root biomass indicating higher rates of root mortality or a stunting effect on root productivity post-second freeze. This finding suggests that cumulative impacts of two freezes occurring less than two years apart are greater than the effects of individual freezes. Increasing root productivity with greater freeze disturbance suggests that recovering standing root biomass may be important for the recovery of above-ground biomass in freeze affected Avicennia. Rapid recovery of below-ground biomass will also contribute to ameliorating rates of soil subsidence and shoreline retreat. Lastly, we found that peat moss is a viable substrate type for future root ingrowth studies if the focus of the study is on total root biomass. However, if a second freeze event occurs during the root ingrowth study, there may be unequal effects between peat moss and local substrate.
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    Don't blame the siblings! Social experiences of gender nonconformity: Does a higher proportion of brothers and negative feedback affect masculinity among sexual minority men?
    (2023-05) Cowan, Alisha; Seidel, Steven; Zaikman, Yuliana; Hawkins, Gina
    Social role theory (Eagly et al. 2004; Eagly, 1987) suggests that individuals who strongly conform to traditional gender roles uphold the hierarchy of the hegemonic male--a model of power, status, and strength—to reap the social benefits of inclusion. Inversely, violations of these roles can cause multiple negative effects of being socially outcasted, being a victim of physical violence, and suicidal ideations (Fiske et al. 2002; Vaughn et al. 2017). Therefore, such experiences lead to a heightened salience of masculine consciousness—consistent presentation of masculinity—for greater social approval (Taywaditep, 2002; 2001). This study aims to explore the relationship between a gay man’s experiences with their sibling’s social feedback about their gender nonconforming behavior and a gay man’s subsequent levels of masculinity. Results of the study failed to provide evidence that sibling composition and negative feedback by siblings affected a gay man’s level of hegemonic masculinity or masculine consciousness. Keywords: Social Roles, Gender Roles, Hegemonic Masculinity, Sexual Minority, Siblings
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    Black mangrove recovery from freeze disturbance accelerated by nutrient enrichment
    (2023-05) Carr, Caleb Cappiello; Proffitt, C. Edward; Devlin, Donna; Withers, Kim; McCracken, Shawn
    Due to climate change, mild winters and fewer extreme freeze events at the temperate-tropical transition zone are allowing some species to migrate poleward, causing shifts in species dominance. In coastal Texas and some other sections of the GOM, woody encroachment by mangrove shrubs and trees into low latitude salt marsh leads to reduced salt marsh dominance likely through competition for light. A recent catastrophic (i.e., mangrove-killing) freeze event in Texas influenced the present regime shift by causing extensive mortality of mature, sapling, and seedling mangroves, alleviating salt marsh vegetation from competition for light. A key topic for study is assessing rate and extent of mangrove recovery following the freeze as a crucial factor impacting the direction, timing, and extent of the regime shift. Additionally, anthropogenic fertilization is predicted to increase and enrich estuaries and bays, resulting in various consequences, such as increased mangrove colonization and dominance, adding another potential impetus to the regime shift. To better understand how nutrient enrichment affects recovery following a catastrophic freeze, fertilization plots were used in a field experiment to ascertain how nitrogen (N) and phosphorus (P) affect black mangrove survival and growth, as well as, changes in the salt marsh vegetation. Other observational sites, with different high and low nutrient conditions, were employed to identify how the findings from the fertilization experiment translate to a larger scale and expand the inference space of the study. Results indicate that nutrient enrichment increased above-ground growth and reproductive output of mangroves, thus enhancing population recovery. Salt marsh species (mainly Batis maritima) reduced growth of mangrove seedlings via inferred competition, although marsh plants did not respond to fertilizer treatments with enhanced above-ground growth. Rather salt marsh was influenced by elevation and shading by mangrove canopy. The findings suggest that nutrient enrichment alters wetland plant dynamics and accelerates a regime shift from a salt marsh to a mangrove-dominated ecosystem, depending on the frequency and magnitude of future freeze events that can reset succession.
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    An assessment of benthic condition in the Matagorda Bay System using a sediment quality triad approach
    (2023-05) Caillier, Jasmine; Montagna, Paul; DeLorenzo, Marie; Pollack, Jennifer
    The Matagorda Bay system is one of seven estuaries along the Texas coast. Once known to be an abundant and diverse ecosystem for marine organisms, however, there has been long-term decline in benthic abundance, biomass, and diversity in the Matagorda Bay System. One possible reason is contamination from municipal, agricultural, or industrial sources, which may be toxic to marine organisms. The purpose of this study was to examine sediment contamination to determine if pollution is a possible cause for ecosystem degradation. Degradation can be indicated by a decline in benthic integrity (i.e., diversity), decreased survival rates of organisms exposed to sediments, and sediment chemical contaminant concentrations over threshold limits. These methods form the Sediment Quality Triad (SQT), which is an interdisciplinary approach that includes contaminant concentrations as a measure of dose, a toxicity measure to assess biological effects, and benthic community diversity to indicate ecological effects. Twenty-four stations were sampled including historical, previously studied sites and sites suspected as having pollution induced degradation. The results revealed that there is contamination but only affecting localized areas in the estuary. The average means (ng/ g dry sediment) across all stations for DDT was 0.07, for PAH the average was 211.87, and for PCBs the average was 0.34. There were no contaminants above threshold limits for PCB, DDT and all but one PAH, but 46% of the stations had chemical detections over threshold limits for seven trace metals: arsenic, cadmium, mercury, copper, lead, nickel, silver, and dibenzo (a,h) anthracene. Mostly near river mouths, 16 of the 24 stations had moderate to high toxicity, and 17 out of the 24 stations had fair to low diversity. Toxicity was significantly correlated with diversity, whereas there were no correlations between sediment chemistry and toxicity or benthic metrics, signifying that there is no evidence that pollution is a problem estuary wide, rather it is localized. This indicates that this system is a multiple stressor system due to various natural influences (changes in temperature, dissolved oxygen, freshwater inflow, salinity) and contamination combined that are affecting benthic communities. With climate drastically changing and more industrialization increasing along the bay the benthic community will face constant declines and more salt or temperature tolerant species dominating. Therefore, focusing on the areas of concern with the most contamination and poor survival and diversity management plans (watershed and non-point sources) can be created to protect this regions ecosystem.
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    Improving the voltage and lifetime of aqueous redox flow batteries utilizing the organometallic catholyte iron (II/III) Tris-2,2’-Bipyridine
    (2023-05) Burghoff, Alexis; Holubowitch, Nicolas; Olson, Mark; Pavel, Ioana
    Renewable energy, such as solar and wind, helps move away from the reliance on fossil fuels, which causes the significant issue of atmospheric carbon dioxide and greenhouse gas emissions. One of the biggest challenges of renewable energy is the lack of storage options so it can be readily available when it is inaccessible (i.e., when environmental conditions change, and solar and wind energy are not accessible). Of the potential energy storage options, electrochemical storage, specifically battery storage, has become popular because of the potential for long-term storage they provide. Some examples of battery storage include lithium-ion and redox flow. While redox flow batteries (RFBs) are an attractive option for long-term energy storage, a lack of suitable high-potential catholyte species hinders the development. Hydrolysis of the charged (oxidized) form typically occurs when the catholyte’s redox potential approaches that of water, leading to performance degradation. Here we show that hydrolysis of an oxidized (charged) organometallic catholyte, which normally leads to severe voltage losses, can be curtailed through interactions with oxidized carbon surfaces. We discovered that the addition of activated carbon cloth (ACC) to the reservoir of low-cost, high-potential iron (II/III) tris-2,2’-bipyridine ([Fe(bpy)3]2+/3+) catholyte-limited aqueous redox flow batteries extends their lifetime and boosts discharge voltage. A similar effect is observed when the cathode is electrochemically oxidized (overcharged) on the first cycle and by modifying electrolyte pH. Oxidized carbons appear to modify the structure of the charged catholyte’s hydrolysis product, the dimer µ-O-[FeIII(bpy)2(H2O)]24+, and/or change the solution pH, permitting its reduction at a more favorable redox potential than in the ACC-free catholyte. Near-neutral-pH RFBs employing 1,1?-bis(3-sulfonatopropyl)-4,4?- bipyridinium ((SPr)2V) anolyte in excess and the with the [Fe(bpy)3]2+/3+ catholyte containing ACC exhibited high-voltage discharge for 600 cycles (41 days) with no discernable capacity fade. We also demonstrate that a zero-pot, solvent-free synthetic method yields long-lived [Fe(bpy)3]2+/3+-based RFBs when employing the novel voltage-boosting methods.
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    Interventions to improve breastfeeding attitudes among college students
    (2023-05) Arreola, Bianca; Houlihan, Amy; Comparini, Lisa; Zaikman, Yuliana
    Breastfeeding is the optimal choice of nutrition for infants as there are numerous health, immunological, and psychological benefits that breastfeeding provides for both mothers and infants. The benefits of breastfeeding are known, however, there are individual and social factors that contribute to mothers feeling worried or nervous about breastfeeding in public; therefore, social support is a key component to mothers achieving their breastfeeding goals. Improving attitudes toward breastfeeding in general, and public breastfeeding in particular, may indirectly provide such social support, which would hopefully create a more welcoming society for breastfeeding mothers. The purpose of this study was to examine the effectiveness of brief interventions in improving attitudes toward breastfeeding among college students. Participants received an information-based, image-based, or information plus image-based breastfeeding intervention (or a control non-breastfeeding intervention). They then completed measures of their attitudes towards breastfeeding in general, attitudes toward breastfeeding in public, and breastfeeding knowledge. Results from this study show that the participants did not differ in their breastfeeding attitudes or knowledge following the interventions.
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    The effects of women's, gender, and sexuality studies courses on the development of privilege awareness and intersectional awareness
    (2023-05) Benkowski, Hanna; Comparini, Lisa; Zaikman, Yuliana; Bartholomay, Daniel
    Privilege is the unearned advantages and benefits an individual experiences based on their gender, race, sexuality, social status, ability, or ethnicity (McIntosh, 1988) while intersectionality posits the interconnectedness of an individual’s social identities that manifest in their life experiences (Collins, 2000; Crenshaw, 1989; Davis, 2008). Privilege studies?(Case, 2007; Case & Rios, 2017) generally focus?on the effect that a single intervention has on one area?of?privilege,?for?example, gender?or race. Fewer?studies (Case, 2012) have analyzed the effects of attending college on?the development of?intersectionality. Building on work showing that the college experience contributes to students’ general identity development (Syed & Amitiza, 2009) and that diversity courses positively influence the development of privilege awareness (Case, 2007; Case & Stewart, 2009), the present study?focuses on whether taking lower-division courses?compared with taking an upper-division?Women’s, Gender, and Sexuality Studies course affects?a student’s?privilege awareness?or intersectional awareness.?Participants (N=118) were attending a Hispanic-serving state university in South Texas with one group (n=75) taking a General Psychology (GP) course and the second group (n=43) taking a WGST course. Demographic data and responses to two surveys were collected using a pre-and post-test design over two consecutive semesters. Results of the GP and WGST students’ scores on both scales indicate no change in their understanding of privilege or intersectional awareness. WGST students, however, demonstrate an overall greater understanding of privilege and intersectional awareness than GP students. Discussion centers on how these results contribute to an understanding of identity development among college students and on ways to improve the measurement of privilege and intersectional privilege for future studies.
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    Exploration of relationships between the hail report sizes and the radar-derived convective features and atmospheric environments from ERA5 reanalysis: A study over the contiguous United States
    (2023-05) Vasquez, Edward Raven; Liu, Chuntao; Shinoda, Toshiaki; Xie, Feiqin
    Hail is a type of frozen precipitation that originates from cumulonimbus clouds with updraft velocities sufficient to suspend hailstones until the terminal velocity of the hail overcomes the updraft velocity. While larger hailstones have been studied extensively due to their significant economic impacts, small hail is also known to cause comparable impacts yet remain understudied due to report biases towards recording larger hail sizes. Consequently, the full spectrum of hail size properties, encompassing both the radar observations and the environmental conditions that produced hail reported at various sizes, is still to be assembled as a unified dataset. To fill this gap, we paired ground hail reports from National Centers for Environmental Information Storm Data, Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) and Meteorological Phenomena Identification Near the Ground (mPING) databases with the attributes of radar-derived convective features and the European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA5) atmospheric vertical profiles to construct a rich dataset. Our study investigates how characteristics of radar reflectivity and atmospheric profiles are related to the size of hail reported over the Contiguous United States, where report density is the greatest and radar network coverage is robust. Convective features extracted from the Multi-Radar/Multi-sensor System (MRMS) allow comparable remote sensing observations of hailstorms. We evaluate the single-polarization radar reflectivity derived Maximum Expected Size of Hail (MESH) performance against reported hail sizes. ERA5 vertical atmospheric profiles are explored to form relationships between the thermodynamic environment including the derived convective indices, hodographs, and the hail sizes. The properties of convective systems and their dynamic and thermodynamic variables in three hail size categories are summarized. Major findings include: • Supplemental datasets, obtained through crowdsourcing and volunteer observers, provide small hail report sizes that align with the broader spectrum of hail properties. • MRMS MESH has some biases toward the reported hail size, as it tends to overestimate small hail and underestimate significant hail sizes. • Hodographs constructed from ERA5 reanalysis vertical wind profiles, composited by region, reveal an apparent increase in low-level streamwise vorticity with increasing hail size. Additionally, regional variations of thermodynamic properties for reported hail events are found in the Contiguous United States. These results provide insights into the relationships between radar observations and atmospheric environments and the sizes of hail, including small hailstones that are often overlooked in previous studies.
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    Communicating passion for work: Examining the relationship between passion, self-determination, and communication behaviors
    (2022-12) Morris, Mark Wayne; Sollitto, Michael; Rodriguez, Stephanie
    During the COVID-19 Pandemic, American workers began leaving their jobs in search of meaningful work for which they felt passionate. This change in the American workforce leads to a new understanding of the role of passion within organizations. Passion has primarily been viewed as a psychological or emotional construct through self-determination theory. This study utilized Vallerand and colleagues (2003) conceptualization of the dualistic model of passion and self-determination theory as the frameworks through which to view passion as a communication construct. This study examined the communication behaviors of voicing dissent, task and relational competence, and workplace relationships as behaviors which fulfill the needs of autonomy, competence, and relatedness, respectively. This study found that each of the communication behaviors were related to the corresponding psychological need. These findings contribute to passion and communication literature by identifying communication behaviors which members may use to communicate their passion. The findings also provide practical insights on how organizations can create cultures and environments that promote healthy communication behaviors that can foster passion within employees.
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    Bonnets & Bullets: The Nancy Hart Militia
    (2023-05) Russell-Adams, Krista M.; Moore, Peter; Wooster, Robert; Robinson, Beth
    For the entirety of the Civil War, a group of elite Southern women from LaGrange, Georgia, formed the only all-female militia ever to have existed in the United States. Known locally as the Nancy Hart Militia, these young women prepared to defend their town, showcasing their determination to protect the home-front and preserve their personal honor while men were away fighting. This thesis explores this little-known group of women, challenging the stereotypes of proper Southern belles and considers their motivations and experiences within the context of antebellum, wartime, and postbellum eras. Using historical records and personal accounts, this study traces the formation of the Nancy Hart Militia, examines their cultural expectations, and analyzes their legacy as they faded into local lore rather than gaining recognition in American history. Ultimately, this thesis argues that in subtly defying societal norms, the Nancies inadvertently created a new space for themselves to challenge gender roles and redefine and defend their honor in the face of danger.
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    Corals in crisis: How temperature and nutrient fluctuations affect physiological responses of corals and their microbiome in K?ne‘ohe Bay, Hawai‘i
    (2023-05) Ruben, Zoe; Bahr, Keisha; Turner, Jeffrey; Abdulla, Hussain
    Coral reefs are the foundation of the social, cultural, and economic life in Hawai?i; however, these reefs have not escaped the conditions that have ravaged coral reefs in other areas. Along the east coast of O?ahu lies K?ne?ohe Bay, which serves as a living laboratory with distinct differences in environmental gradients due to variations in circulation and residency times. This provides a unique opportunity to explore the impact of water quality and ongoing ocean warming on coral health, susceptibility, and tolerance. Pairs of historically bleached/non-bleached corals were collected at two sites within K?ne?ohe Bay and subjected to experimental treatments varying in temperature and nutrient levels for one month at the Hawai?i Institute of Marine Biology. Biological response variables were measured, and subsamples were taken from the coral fragments at the beginning and end of the experiment for bacterial community analysis. Results demonstrate that coral decline and bleaching susceptibility were least prevalent in the Control and Elevated Nutrient treatments but most prevalent in the Elevated Nutrient + Elevated Temperature treatment, indicating that low-level nutrients may benefit the corals. Still, the combined stressors may have a synergistic, negative effect. Microbial clustering analyses reveal a shift in relative abundances of bacteria before vs. after exposure to stress. These findings may support that coral bleaching susceptibility is manifested throughout the coral holobiont and that physiological response to interactive stressors can be better understood and potentially mitigated.
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    Evaluating the use of drones for monitoring waterbird nest abundance and nest survival
    (2022-12) Mirzadi, Rostam; Gawlik, Dale; Stunz, Greg; Starek, Michael
    Surveys of colonial waterbirds are used to monitor species’ population dynamics, contaminant levels, and to derive metrics that can be used to assess wetland ecosystem restoration and management. Previous studies have found that drone surveys provide accurate estimates of nest abundance and survival for ground-nesting waterbird species such as terns (Laridae Spp.), but drones have not been used to estimate survival for waterbirds nesting in a canopied marsh habitat, and potential sources of bias in drone surveys have not been examined in depth. We examined potential visibility biases associated with using a drone to survey colonies of wading birds (Ciconiiformes and Pelecaniformes) in marsh habitat in Florida in 2020 and 2021. Monthly nest counts and survival were compared between traditional (combination of fixed-wing aircraft and ground surveys) and drone survey methods. Ground-based and drone nest transect surveys were conducted to estimate survival and detection probabilities of each species and plumage color. Generalized linear mixed-effects models were used to quantify the degree to which visual occlusion of nests in?uenced detectability. Estimates of white-colored waterbird nests were significantly greater for drone surveys than those derived from traditional survey methods but estimates of dark-colored waterbirds from drone surveys were biased low. Variation in detection was best explained by canopy cover, plumage color, and nest stage. Overall, there was no difference between survival estimates from either method. However, drone-derived estimates of dark-colored waterbirds had lower accuracy. Our results suggest that drone surveys are a viable method to conduct monthly nest surveys and estimate survival of waterbirds breeding in marsh habitat, but researchers should consider their study area and species before choosing a survey method.
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    SECURENN: Defeating adversarial neural network attacks with moving target defense and genetic algorithms
    (2023-05) Romero, Laila Maria; Rubio-Medrano, Carlos; Wang, Wenlu; King, Scott
    Neural Networks (NNs) have become a critical part of Artificial Intelligence due to their reputation of producing highly accurate outputs with minimal human assistance. NNs are used in various diverse implementations from housing market predictors to medical imaging. Their swift increase in importance and incorporation into our lives have rendered them valuable targets to Adversarial Attacks. Adversarial Attacks are malicious actions aimed to undermine NN model performance, cause misbehavior, and acquire protected information. NNs are used to run many state-of-the-art image classification systems therefore, attacks could be dangerous to the property, health and safety of their users. The most common and successful attacks are gradient based attacks on Image Classification Neural Networks. The defense strategies in existence, such as Adversarial Training, fall short on their ability to protect models against more complex attacks due to their susceptibility to degrade generalization ability in models. This work proposes SecureNN, a defense framework for image classification NNs to increase overall robustness of the models against white-box untargeted Adversarial Attacks. Through the combination of the well- established cybersecurity and Machine Learning techniques of Moving Target Defense, Genetic Algorithm, and Ensemble Learning, SecureNN is able reduce the degraded generalization ability seen in most defense methods as well as minimize the advantages white-box attacks have without incurring in significant cost on the accuracy and speed of the model. SecureNN has been tested extensively on the following four NN architecture types: CNN, ResNet50, Inception, and Inception-ResNet and trained with three common datasets of MNIST, ImageNet and Cifar-10. Each model architecture and dataset were tested against the four highest error rate gradient-based attacks of Fast Gradient Sign Method, Basic Iterative Method, Projected Gradient Descent and Carlini Wagner. The average of 1.5% higher accuracy rates than Adversarial Training and 49.6% higher accuracy rates than Undefended Models exhibited through the experimental phase of our framework substantiates SecureNN’s potential as a defense mechanism effective in increasing NN robustness.
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    Autonomous harvesting via hierarchical reinforcement learning in dynamic environments
    (2023-05) Nethala, Prasad; Huang, Yuxia (Lucy); Dugan, Um; Starek, Michael
    Smart farming not only requires geospatial navigation but also uses various microprocessors and sensors to perform functions such as controlling temperature and irrigation systems. Advanced phenotyping modalities such as IoT and digital twin technologies revamped agriculture productivity to an extent hitherto unprecedented. However, matching crop cultivation and harvesting technology has yet to be further advanced to take advantage of data-driven crop production. Farming areas are often unstructured with dynamic objects such as human workers and farming machines. Therefore, a smart harvesting robot is in need of automatic navigation and obstacle avoidance. Due to conflicting objectives of goal-reaching and obstacle-avoidance, especially in a dynamic environment, harvesting is a challenging task for a robotic system. In this thesis, a novel Hierarchical Reinforcement Learning architecture is proposed, which is a robust multitask-capable AI model for an autonomous mobile manipulator to achieve both terrain coverage while assuring obstacle avoidance with dynamic objects. It is assumed that the manipulator is equipped with sensitive skin for omnidirectional sensitivity. The proposed Hierarchical Reinforcement Learning architecture is modeled with both Deep Deterministic Policy Gradient (DDPG) algorithm and Proximal Policy Optimization (PPO) algorithm. As a result, two different hierarchical architectures are developed as Hierarchical Deep Deterministic Policy Gradient (HDDPG) and Hierarchical Proximal Policy Optimization (HPPO) algorithms to autonomously manage two separate agents for both goal-reaching and obstacle-avoidance objectives. Transfer learning is adopted to assess if the trained models were overfit or underfit as well as for learning generalized policy. The algorithms were evaluated in a simulated environment by collecting fallen fruits in a crowded orchard farm environment with a variety of dynamic obstacles after being taught in a simple environment with fewer constraints. The metric used for this mission includes percent harvesting and the number of goal touch, the number of obstacle touch, navigation distance, and navigation time. HDDPG outperformed the remaining algorithms by 70% in terms of total average rewards and minimum pixel distance travel, whereas HPPO achieved the highest number of fruit collections, DDPG and PPO were unable to complete the test environment due to local minimum. Both Hierarchical architectures HDDPG and HPPO could successfully generalize to new situations beyond the training environments with robust performance.
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    Beyond the writing: Students' perspectives of the Casa Writing Center
    (2023-05) Riojas, Brenda Elaine; Murphy, Susan; Pina, Manuel; Sollitto, Michael; Hinojosa, Yndalecio
    As an MA student in English studying writing center theory, I planned my thesis project around the CASA Writing Center services and the students who seek assistance with papers, projects, reports, and other writing needs across disciplines. In this study, I gathered qualitative data from students who visited the CASA Writing Center to answer the research question, Why did the student visit the CASA Writing Center that day and how did that experience make them feel? I gathered qualitative survey data because I wanted to explore what led students to the writing center and how they felt after receiving assistance from a tutor. This approach was the best approach because it calls attention to the implicit details of students’ thoughts and experiences related to the writing center. I surveyed 71 participants that met the following requirements: that they must be 18 years or older, must be enrolled as a full-time student, and made a tutoring appointment during the fall 2022 semester. Participants were asked the same nine open-ended questions on paper surveys. To analyze the data, I used a thematic approach because it allowed a deeper understanding for each participant’s reasoning for visiting the writing center. In this thesis, I will present the two major themes that appeared in my qualitative data, which were the writing center’s physical environment and the writing development of students. For the physical environment theme, students expressed interest with the setup and amenities of the writing center. Within this theme, the variants include the lounge area, computer section, and provided snacks and coffee. As for the writing development theme, variants detected in the data include students self-proclaiming themselves as “writers,” participants that sought assistance with APA format, and the writing resources provided to participants. The benefit of this study is to further understand how the writing center serves and impacts its students and adds to writing center literature concerning the physical environment.
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    The effect of backpack load on gait biomechanics in college-aged individuals
    (2023-05) Morales, Breanna; Applequist, Bryon; Spaniol, Frank; Park, Jangwoon
    The aim of this study was to investigate the effects of backpack load carriage on gait and lower extremity biomechanics in healthy college-aged students. A total of 14 participants completed gait trials while walking carrying a backpack weighing 20% of their body weight and without a backpack. The kinematics, kinetics, and spatiotemporal parameters of gait were analyzed under both unloaded and loaded conditions. The results of the study showed that load carriage had a significant impact on several kinematic variables. Participants exhibited a decrease in hip flexion range of motion and knee flexion and extension peak velocities when carrying a load. This suggests that load carriage alters the normal movement patterns of the lower extremities during the gait cycle. Additionally, several gait kinetic variables were found to be significantly different between the unloaded and loaded conditions, including mean peak vertical force, mean peak mediolateral force, mean peak propulsion, mean peak brake, hip flexion peak moment, and ankle plantar flexion peak moment. These results indicate that load carriage not only affects the movement patterns of the lower extremities but also alters the forces acting on the body during walking. The findings of this study are consistent with previous research and suggest that load carriage should be considered when choosing a backpack or occupational tasks that involve load carriage. However, it is important to note that the effect of load carriage on gait biomechanics may depend on several factors, such as the weight and distribution of the load. The limitations of this study included the backpack weight being too heavy for some participants, leading to discomfort in their shoulders, and the inability to increase the weight of the load for safety reasons. Future studies could investigate these factors and explore optimal load carriage conditions. In conclusion, this study provides valuable insights into backpack load carriage on gait biomechanics in college-aged adults. The findings suggest that load carriage significantly alters gait patterns and should be taken into consideration when selecting a backpack or when involved in occupational tasks that require load carriage.
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    Artificial neural networks for approximating the solutions to nonlinear ordinary differential equations
    (2023-05) Martinez, Mara Rose; Muddamallappa, Mallikarjunaiah; Ekici, Celil; Palaniappan, Devanayagam
    Artificial neural networks (ANNs) are the computer archetype of biological networks in the human brain. An ANN is a group of interconnected nodes stacked in layers and each layer is connected with its preceding and succeeding one via specified weights. The numerical algorithms based on ANN have been shown to perform well in approximating the differential and integral operators. In this thesis investigation, a neural network architecture is proposed for approximating the numerical solutions to the nonlinear ordinary differential equations. A comparative study is performed between the ANN predictions and the approximation obtained from finite element method (FEM). The solution finding problem using ANN is formulated as a minimization of a total loss function, an L2-type function or root mean square type function, which is a sum of differential equation loss and the boundary loss terms. For the minimization, a feedforward-type unsupervised neural network architecture is examined in this thesis. Recent works have shown that such an unsupervised minimization yields highly accurate prediction which can approximate the numerical solution to the differential equation. However, currently no study is available in the literature on a comprehensive unified ANN method with particular choice of the loss function and network’s hyperparameters and how such choices influence the accuracy of the network prediction. In this thesis, we addressed some issues concerning the design of the network to obtain highly accurate numerical results. The sensitivity in the network’s accuracy with respect to the size of the training data, activation functions, optimizers, number of hidden layers, and the number of neurons in each hidden layer is also studied. Our trail solution consists of two parts: the first part satisfying the differential equation; the second part stems from satisfying boundary conditions. At the training phase access to the exact solution is not needed, however, the network adjusts its training based on the linear interpolation of the randomly chosen data points from the computational domain. A backpropogation step is needed for a calibration of the network parameters to obtain accurate prediction. We investigate the proposed ANN method to approximate the numerical solutions to two nonlinear boundary value problems from fluid dynamics: Electrohydrodynamic fluid model; one-dimensional Darcy-Brinkman-Forchheimer model. A comparison of the network solution is made with that of the one obtained from classical continuous finite elements. We report that ANN method developed in this thesis performs better in achieving higher accuracy within the fewer number of data points. We believe that the proposed architecture along with the “correctly” chosen hyperparameters constitute a better numerical approximator for the partial differential equations in higher dimensions.
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    Nitrogen and phosphorus budgets in estuaries of the Texas Coast
    (2023-05) Marshall, Danielle; Montagna, Paul; Hu, Xinping; Wetz, Michael
    Estuaries are highly valuable ecosystems that depend on nutrients for their productivity. On-going urbanization and socio-economic activities are constantly affecting nutrient dynamics and estuarine organisms. The purpose of this study was to determine how hydrology affects nutrient budgets in Texas estuaries through biogeochemical budget modeling under the land-ocean interaction in the coastal zone (LOICZ) guidelines. LOICZ budgets were applied to the seven major estuaries in Texas to address the long-term water, salt, and nutrient budgets to calculate daily averages using various datasets from multiple agencies. The Laguna Madre Estuary was further separated into two budgets: the Lower Laguna Madre Estuary and the Upper Laguna Madre Estuary. The results revealed that the climate gradient plays a crucial role in the water budgets indicating that precipitation is a main driving factor to inflow balance. In addition, inflow balance is a main driving factor to salinity and nutrient concentrations among these estuaries. However, external factors such as urbanization, return flows, and agricultural runoff have elevated the nutrient levels in two estuaries. The Trinity-San Jacinto Estuary had higher daily average dissolved inorganic phosphorus (DIP) and total phosphorus (TP) levels compared to the other estuaries due to the large population density of Houston, TX, and the frequent use of detergents and possible fecal and urine waste in wastewater return flows. In contrast, the Upper Laguna Madre Estuary higher total Kjeldahl nitrogen (TKN) compared to the other estuaries due to its unique geographical features and inflow primarily dominated by sewage and agricultural runoff. The implications of these results are that altered hydrology can alter the nutrient dynamics of these estuaries and can affect biological productivity and water quality in an estuary.
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    Socio-Economic drivers of surface water quality impairment
    (2023-05) Kramer, Mary Louise; Wetz, Michael; Wowk, Katya; Yoskowitz, David
    Water quality is a key factor in ecosystem health. While physical and ecological models of pollution have been widely used to determine water quality, there is a significant gap in the use of socioeconomic metrics in these models. The purpose of this study was to identify and visualize social, cultural, behavioral, and economic drivers of surface water quality impairment. Standardized socio-economic data with links to water quality data were mapped across two study sites: San Antonio Bay and Baffin Bay. A binomial logistic regression model was utilized to identify connections between socio-economic metrics and water quality impairment status. In the San Antonio Bay study site, important predictors of surface water quality impairment were housing type and transportation vulnerability, percentage of 5% or more impervious land cover within 30m if shoreline, amount of developed area, and forest and woody wetland cover. In the Baffin Bay study site, important predictors were minority status and language vulnerability, percentage of 5% or more impervious land cover within 30m of shoreline, forest and woody wetland cover, and amount of cropland. Understanding the interactions between communities and local water quality will allow for more thorough and effective management of water resources.
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    The role of MIR-199A in BAO-induced transgenerational bone deformities in Japanese Medaka
    (2023-05) Jayarajan, Rijith; Seemann, Frauke; Bird, Christopher; Portnoy, David; Lu, Yuan
    Benzo[a]pyrene (BaP), a ubiquitous environmental pollutant and known carcinogen, has been evidenced to cause bone disorders in a transgenerational manner by altering epigenetic mechanisms like microRNAs (miRNA). Transcriptome analysis of bone tissue in the ancestrally BaP-exposed F3 generation indicated a prominent role of miR-199a in the regulation of significantly enriched molecular pathways for bone formation and oxidative stress. To elucidate the function of miR-199a during bone development wildtype (Orange Red) and transgenic (twist:dsred/col10a1:gfp and col10a1:gfp/osx:mCherry) freshwater medaka (Oryzias latipes) were assessed for calcification and cell-subpopulation level changes in response to miR-199a agonist and antagonist microinjections at the onset of vertebra development. To further characterize the role of miR-199a on bone development, mineralization and osteoblast differentiation, the effects of miR199a-3p agonist and antagonist injections (700 pg) at the beginning of bone formation in medaka embryos 3 days post fertilization (dpf) were studied. The area and intensity of calcification were assessed in wild-type medaka. Medaka transgenic lines - twist:dsred/col10a1:gfp and col10a1:gfp/osx:mCherry were used to assess changes during osteoblast differentiation. No impact on the calcified area and bone thickness upon miR-199a-3p agonist or antagonist injection was identified. The spatial distribution and the cellular density of twist+ mesenchymal stem cells (MSCs) were not affected. A significant reduction upon agonist injection was noted in the cellular density of col10+ osteochondro progenitors (OPCs). No change in spatial distribution and density of osx+ premature osteoblast cells (POCs) was seen upon miR-199a-3p treatment. Assessment of bone gene expression levels in 25 dpf old medaka larvae revealed a potential inhibitory effect of miR-199a-3p on bone development. The tissue, cellular and molecular level experiments confirmed the role of miR-199a-3p in bone maturation and osteoblast differentiation. This study provides a novel understanding of miRNA regulation during two critical windows of bone development. The provided data can be used to delineate the effect of BaP exposure on regulating specific miRNAs. Moreover, developmental levels of miR-199a may be useful as a potential biomarker for later life-stage bone impairment, such as osteoporosis development.