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Nature of Science in Science Education: Establishing Common Ground
No full textA deep and robust understanding of the nature of science (NOS) has been increasingly recognized as a core component of any form of meaningful scientific literacy. However, little progress has been made with NOS teaching and learning over the past century. This has become an increasingly problematic situation as citizens have struggled with numerous high-profile socioscientific issues over the past several decades (e.g., climate change). Unfortunately, scholars��� discordant approaches to NOS in science education have created an acrimonious environment that has likely impeded efforts to promote attention to NOS teaching and learning. This problematic state of affairs is exacerbated by a lack of clarity regarding the specific ways that NOS understanding affects SSI decision-making, and a dearth of quantitative instruments that can provide valid and reliable inferences about respondents��� understanding of NOS constructs. This dissertation research contributes to the improvement of NOS teaching, learning, and research by: (1) Identifying the major themes that exist within the NOS approach literature, along with the areas of agreement and disagreement related to each theme; (2) Determining the NOS constructs related to climate change beliefs and attitudes; and (3) Creating a novel, high-resolution, quantitative NOS instrument that targets a specific NOS construct (i.e., methodological pluralism). The thematic analysis of NOS approach literature yielded seven central themes that contained numerous areas of agreement and disagreement that can help to provide order to future scholarly discussions. The examination of NOS connections to climate change beliefs and attitudes within the literature identified 15 relevant NOS constructs that provide an important focal point for science educators, communicators, and researchers. Instrument development efforts resulted in a tool that can provide high-resolution, valid, and reliable inferences about students��� views regarding methodological pluralism. While further refinement of the instrument is needed, this work represents a significant advance in quantitative NOS assessment. Collectively, the research related to this dissertation has addressed several important gaps in the field of NOS education, and establishes an important future line of research
Targeted Therapeutic Strategies Against Triple-Negative and Metaplastic Breast Cancers
No full textBreast cancer is the second most common cause of cancer mortality in women in the United States. As a heterogenous disease, breast cancer is clinically classified by expression of estrogen receptor (ER), progesterone receptor (PR), and overexpression/amplification of human epidermal growth factor receptor 2 (HER2). Triple-negative breast cancer (TNBC), i.e., those not expressing ER, PR, or HER2, represent ~10-20% of all breast cancer cases, has the worst prognosis in comparison to ER+ or HER2+ breast cancers.
Gene profiling analysis has identified TNBC subtypes with unique molecular signatures that may be therapeutically targeted. Among the six known TNBC molecular subtypes, the mesenchymal subtype comprises 30% of all TNBCs and has the worst disease-free survival compared to other TNBC subtypes. Metaplastic breast cancer (MpBC) is a highly aggressive, and metastatic breast cancer malignancy that typically falls under the mesenchymal TNBC subtype, accounting for <5% of all invasive breast cancers. Patients with MpBC are generally diagnosed at a later age with a more aggressive disease, likely contributing to their dismal median survival of 8 months after metastasis. There are no standardized therapeutic options for patients with MpBC.
MpBC is characterized by one or more cell populations that have undergone metaplastic differentiation, i.e. cells convert from glandular to non-glandular morphology. MpBCs are enriched with epithelial-to-mesenchymal (EMT) and cancer stem cell (CSC) markers, with hyperactivation of phosphoinositide-3-kinase (PI3K) pathway and enhanced nitric oxide (NO) production. Patients diagnosed with metaplastic TNBC have a significantly worse prognosis compared to non-metaplastic TNBC (non-MpTNBC). Thus, the development of effective therapies for women with MpBC and non-MpTNBC represents a significant unmet clinical need.
The focus of my dissertation has been on evaluating novel therapeutic strategies in the preclinical setting to treat MpBC and non-MpTNBC. Using human breast cancer cell lines and patient-derived xenograft (PDX) models, my preclinical studies focused on evaluating targeted therapies, such as utilizing monoclonal antibodies against EGFR to treat TNBC, as well as combining PI3K and nitric oxide synthase (NOS) inhibitors to treat MpBC. I found that combined PI3K and NOS inhibition reverses EMT, decreases CSC populations, rendering MpBC tumors more chemosensitive
The Effects of Culturally Tailored Agricultural Literacy Curriculum Among Latino Youth Behavior
No full textAgriculture and nutrition are tightly intertwined as each relies heavily on the other to support the Nation���s food system and the consumers it feeds. Unfortunately, the urbanization of our communities has triggered a divide between farmers and their consumers. This is made evident by the general population lacking an inadequate level of agricultural literacy. Partnered with this decline, an insidious health problem, childhood obesity, has increased in America���s youth. It is important to recognize that there is a higher prevalence of this health disparity among the Hispanic population. Through the lens of the social cognitive theory, the researchers aimed to assess the impact of culturally relevant agricultural literacy lessons have on Latino youths��� agricultural literacy levels and nutrition attitudes and behavior scores. The objectives of this study were achieved by implementing two interventions, the comparison and treatment, to youth after-school and summer programs located in Central and South Texas. The comparison group received the standardized agricultural literacy curriculum from the National Agricultural Literacy Matrix. The treatment group received the culturally tailored version of the curriculum. The pre and posttest data were analyzed by t-tests and repeated measures ANOVA. Regardless of intervention, the agricultural literacy levels of youth increased from pre to posttest which provides researchers with evidence of the positive impact of youth engaging with nutrition based, agricultural literacy curriculum. The youth who engaged with the culturally relevant agricultural literacy curriculum had a positive gain in their nutrition attitudes and behavior scores. Conversely, the comparison group did not have significant change in their nutrition scores. The novelty of this research provides valuable insight to scholars in the agricultural literacy field as it underscores the importance of providing a space for youth to connect their cultural background and experiences while interacting with lessons that highlight the relationship of the agricultural industry and nutrition
An Epidemiologic Investigation on Arsenic Exposure and Its Association with Mental Health Outcomes
No full textMental health problems, characterized by a clinically important disturbance in cognitive, emotional, or behavioral aspects of an individual���s life, have garnered growing interest in the field of epidemiology due to their complex causal mechanisms, increasing prevalence, and substantial burden on modern populations. There are many causal factors suspected to impact mental health, mental illness, and emotional wellbeing including certain environmental toxins, like arsenic, although these associations are not well established. Arsenic has been shown to be a globally toxic substance that is associated with numerous health problems. Recent studies suggest that arsenic may have an impact on mental health due to its neurotoxicity.
The present research investigates the possible association between arsenic and mental health problems through a systematic review, geographically weighted regression on a county level for the 48 contiguous states with soil arsenic, and a geographically weighted regression on a county level for Texas with water arsenic exposure estimates. The systematic review demonstrated associations between Arsenic and multiple mental disorders as well as generally poor mental health. The first geographically weighted regression of the contiguous 48 states found that soil arsenic was a significant predictor of both county suicide rates and the years of potential life lost due to suicide rate. The second geographically weighted regression found that estimated water arsenic exposure was a significant predictor of both county suicide rates and number of days reported with poor mental health.
The present research suggests that arsenic may be a potential environmental risk factor for mental health outcomes. Further prospective studies with individual-level data are necessary to confirm causality and explore the interactions with other risk factors
Family Involvement in Literacy-Infused Science Learning for Texas Rural Youth and Communities
No full textWhile much research has studied children���s informal science learning with their families at exhibitions, museums and after-school programs such as family science nights, limited research has explored family science learning using take-home science activity kits. To better understand how home science activity kits are developed and implemented to support children���s informal science learning, a systematic review was first conducted. In the second study, I described the development of Family Involvement in Science (FIS) activity kits, one of the innovative components of a larger federal funded research grant in Texas. Seven rural fifth-grade Hispanic students and their families��� home science learning experiences were compared with seven non-rural counterparts using a comprehensive and reliable multi-dimensional and multi-categorical observation instrument called Family Involvement in Science Observation Protocol (FISOP). Students��� and family members��� time allocation participating in scientific practices, including use of strategies, activity structures, communication modes, language of content, and language use were observed and analyzed using the chi-square tests of homogeneity. Statistically significant differences were found in nine out of ten sub-domains between rural and non-rural families. In the third study, family was viewed as a socio-cultural learning environment that empowered parent-child science conversations as they actively engaged in FIS activities. Parent-child science talks from nine rural Hispanic families were captured through two pairs of GoVision camera goggles, and the videos were collected, screened, transcribed, and coded using two qualitative coding schemes: literacy-infused science strategies and scientific behaviors. The findings provided initial evidence that FIS encouraged Hispanic rural children and their parents to use scientific inquiry-based approaches and strategies in scientific conversations and activities
Prototype of a Bi-Directional Digital Twin of an Industry 4.0 Smart Manufacturing Facility
No full textThis thesis presents a pioneering exploration into the development and practical application of a bi-directional digital twin prototype within the context of Industry 4.0 smart manufacturing. Bridging the gap between the physical and digital realms, this research addresses the emerging need for advanced digital replication and interaction mechanisms capable of enhancing operational efficiency and educational processes in modern manufacturing environments. By integrating technologies like Siemens TIA Portal, NetToPLCSIM, and OPC UA Server, with a sophisticated communication framework, the study establishes a seamless, real-time bi-directional communication between a physical model and its digital counterpart. The results demonstrate the system's capability to accurately mirror actions and movements across the physical and digital domains, highlighting its potential to revolutionize manufacturing processes, predictive maintenance, and training methodologies. This work not only contributes to the theoretical understanding of digital twin technologies but also showcases a tangible implementation, paving the way for future research and the broadening of digital twin applications across various sectors of the industrial domain
Effect of Sample Size on Linear Elastic Fracture Toughness of FFF-Processed PLA Compact Tension Specimens
No full textThe "Effect of Sample Size on Linear Elastic Fracture Toughness of FFF-Processed PLA Compact Tension Specimens" investigates the impact of sample size on the fracture toughness of 3D printed Polylactic Acid (PLA) using Fused Filament Fabrication (FFF) technology. ASTM D5045 standard is widely recognized and employed as a benchmark for evaluating the fracture toughness of materials within the linear-elastic fracture mechanics (LEFM) domain. This research aims to assess the applicability of this standard for evaluating fracture toughness in additive manufacturing thermoplastic materials focusing on the influence of specimen size, among other parameters, on the material's mechanical properties. Through a comprehensive experimental setup involving various sample sizes, infill sizes, and layout patterns, the study provides a detailed analysis of fracture toughness behavior through numerous tests. The findings reveal significant dependencies of fracture toughness on the sample size, indicating a deviation from true plane strain conditions and highlighting the necessity of reporting conditional stress intensity factors (����_����) for this particular case. The research contributes valuable insights into the mechanical characterization of 3D-printed thermoplastic materials and suggests practical implications for improving additive manufacturing testing and evaluation practices
Influence of Microstructural Components on Hydrogen Embrittlement in Alloy 718: Insights from Friction Stir Processing and Additive Manufacturing
No full textHydrogen can cause severe embrittlement of high-strength metal alloys. Nickel alloy 718, a high-strength and corrosion-resistant alloy widely used in the aerospace and oil & gas industries, is highly susceptible to hydrogen embrittlement (HE). The premise of this work is to explore thermomechanical processing to obtain unique fine-grained microstructures in alloy 718. By employing electrochemical hydrogen charging, it aims to advance the understanding of the role secondary phases and grain boundaries (GBs) play in HE behavior. The overarching goal is to identify and propose strategies for the design of HE-resistant alloys.
Firstly, the effect of grain size and precipitates on HE susceptibility is investigated. Under tensile loading, the friction-stir processed and aged (FSP-A) condition with refined grains and precipitates showed substantially reduced HE susceptibility with 12.6% loss of ductility due to hydrogen as measured by reduction in area compared to the coarse grained peak-aged (PA) condition, which lost 29.9%. However, the FSP (with fine grains) and solution-treated (ST, with coarse grains) conditions prior to being aged display similar susceptibility to HE, despite higher hydrogen uptake in the former. The finding that microstructures with refined grains absorb more hydrogen yet have similar or reduced HE susceptibility, demonstrates their HE resistant character.
Secondly, the role of GB character distribution on HE susceptibility in fine-grained alloy 718 was evaluated. Three FSP cases, processed at rotational speeds of 200, 250, and 300 rpm, respectively, with a constant feed rate of 50 mm/min, produced 57%, 65%, and 53% high angle GBs (HAGBs), respectively. Tensile test results show that a high fraction of HAGBs in the microstructure can be correlated to higher HE susceptibility.
Finally, microstructures and properties of alloy 718 produced by selective laser melting (SLM) and subjected to heat treatments (HTs) were investigated. The as-printed material contained 4.7��0.8% volume fraction of the Laves phase, which is reduced to 0.2��0.1% after HT at 1150��C for 2 h. Tailored produced mechanical properties meeting API A6CRA requirements. HE behavior of SLM alloy 718 was similar to wrought alloy 718, with as-printed and aged conditions exhibiting higher HE susceptibility than solutionized conditions, likely by similar HE mechanisms
Family Involvement in Literacy-Infused Science Learning for Texas Rural Youth and Communities
No full textWhile much research has studied children���s informal science learning with their families at exhibitions, museums and after-school programs such as family science nights, limited research has explored family science learning using take-home science activity kits. To better understand how home science activity kits are developed and implemented to support children���s informal science learning, a systematic review was first conducted. In the second study, I described the development of Family Involvement in Science (FIS) activity kits, one of the innovative components of a larger federal funded research grant in Texas. Seven rural fifth-grade Hispanic students and their families��� home science learning experiences were compared with seven non-rural counterparts using a comprehensive and reliable multi-dimensional and multi-categorical observation instrument called Family Involvement in Science Observation Protocol (FISOP). Students��� and family members��� time allocation participating in scientific practices, including use of strategies, activity structures, communication modes, language of content, and language use were observed and analyzed using the chi-square tests of homogeneity. Statistically significant differences were found in nine out of ten sub-domains between rural and non-rural families. In the third study, family was viewed as a socio-cultural learning environment that empowered parent-child science conversations as they actively engaged in FIS activities. Parent-child science talks from nine rural Hispanic families were captured through two pairs of GoVision camera goggles, and the videos were collected, screened, transcribed, and coded using two qualitative coding schemes: literacy-infused science strategies and scientific behaviors. The findings provided initial evidence that FIS encouraged Hispanic rural children and their parents to use scientific inquiry-based approaches and strategies in scientific conversations and activities
Relaxation Dynamics and Thermal Properties of Polyelectrolyte Complexes and Multilayers
No full textPolyelectrolyte complexes and multilayers (PECs and PEMs) are prepared by mixing two oppositely charged polyelectrolytes and by layer-by-layer assembly respectively. PECs and PEMs find applications in drug delivery systems, humidity sensors, electrochemistry, separation membranes, and many more. The key to these applications is understanding the dynamics of polyelectrolyte (PE) chains in PECs and PEMs. The dynamics of PE chain in PECs and PEMs is influenced by temperature, hydration, pH, salt, solvent quality, PE type and, many more. This dissertation discusses two studies on the impact of temperature, water, pH, and, salt on the dynamics of PE chain in PECs and PEMs. Additionally, we also study the influence of salt type on glass transition temperature of PECs.
In the first study, we discuss the impact of salt type on glass transition temperature (Tg) of PECs composed of PSS and poly(diallyldimethylammonium chloride) (PDADMA). We specifically examine the effect of anion type (NaCl, NaBr, NaNO��� and NaI) on Tg. First, we evaluate the effect of salt type on doping of PECs using nuclear magnetic resonance (NMR) and neutron activation analysis (NAA). Next, we evaluate the Tg at different hydration levels using modulated differential scanning calorimetry (MDSC). Put together, these studies give insight into how different parameters such as water, pH, salt and salt type influence the dynamics and relaxation of PE chain in PECs and PEMs.
In the second study, we discuss the effect of temperature, water and pH on relaxation times solid PECs composed of poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). It has been previously shown that water, pH and salt concentration impact the glass transition temperature of hydrated PECs. The effect of salt on relaxation times in PECs has been well documented. However, knowledge is lacking on the effect of water and pH on relaxation times in hydrated PECs. This is accomplished by performing time-temperature, time-temperature-water and time-temperature-water-pH superpositions.
In the third study, we discuss the impact of salt concentration on diffusion coefficient of PE in PECs using fluorescent recovery after photobleaching (FRAP) in PECs composed of poly(styrene sulphonate) (PSS) and poly(vinylbenzyl trimethylammonium chloride) (PVBTMA). We first map out the phase diagram at room temperature using optical microscopy, UV-Vis spectroscopy and conductivity measurements. Next, we study the diffusion of counterions using a home-built setup. Finally, we study the lateral diffusion of fluorescently tagged PVBTMA using confocal microscopy.
In the fourth study we discuss the impact of solvent on the lateral diffusion of PVBTMA in PSS-PVBTMA PEMs. First, we study the effect of varying weight % of ethanol and urea on the growth of PEMs. Next, we discuss the effect of varying weight % of ethanol and urea on the strength of interaction between the PEs using Isothermal calorimetry (ITC)