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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)
Cricket Song Classification Using Transformers
No full textAs interest in studying animal sounds for biodiversity monitoring grows, the need for automatic methods to classify species based on their unique songs becomes crucial. This thesis presents an innovative approach to identifying various cricket species and genera by analyzing their audio recordings through advanced pretrained transformer models, specifically utilizing the AST (Audio-Spectrogram Transformer). The dataset includes 592 audio files for Gryllus species and 441 audio files for different genera and is meticulously curated to overcome challenges like uneven class distribution and variations in audio file durations. Customized label mapping and strategies such as undersampling and oversampling are applied to adapt the pretrained model to the specific classification task and balance the dataset respectively. The experimental setup includes three to four distinct datasets, each focusing on different subsets of cricket species and genera each. Training involves varying learning rates, with evaluation metrics encompassing validation and training accuracy, precision, recall, and F1-score. Further analysis is conducted to visualize the distribution of the data points. For this, first, Principal Component Analysis (PCA) is used to reduce the dimensionality of the features. Next, t-SNE visualization is used to provide insights into the spatial relationships between different species in the data space. This work differentiates itself from previous approaches that used CNNs, and it explores the capabilities of transformers in classifying cricket species and genus and aims to understand how these models perform in comparison. The transformer model achieved high accuracy rates of 95.31% for classifying Gryllus species and 94.27% for genus classification. This study has potential applications in education, conservation, agricultural pest management, and other ecological studies
Reducing Risky Driving Behaviors by Considering Personality Factors
No full textTraffic accidents at intersections have been a concerning issue that negatively affects driving safety, with nearly 1000 people are killed in traffic accidents involving running red lights every year. However, driving safety issues at traffic light intersection remains understudied compared with other driving safety topics such as aggressive driving or distracted driving.
Current driving studies show that driving safety and driving behaviors are affected by many individual characteristics, such as age, sex, and personality. While other individual characteristics have been deeply studied, personality, as a well-developed and widely recognized individual characteristic, has not been given equal amount of attention in the study field of driving safety and behaviors.
In this dissertation, three studies were designed and conducted to further investigate the relationship between personality and risky driving behaviors. Data analysis results showed a strong correlation (R = 0.74) between the category of extraversion/introversion personalities and risky driving behaviors, meaning that the more extraverted the person is, the more risky driving behaviors they tend to exhibit. Theory on personality suggests that this is because extraverts are not as capable in perceiving risk-related information from the driving context compared to introverts. Targeting these characteristics, this research showed that increasing information salience and redundantly displaying information can help reduce risky driving behaviors, especially among extraverts.
The findings from this dissertation provide contributions in both scientific and practical aspects. For the scientific aspect, this dissertation provides a foundation of studying the relationships between personalities and risky behaviors in fast-paced real-life decision-making scenarios, such as driving. Moreover, this dissertation helps draw research attention to some understudied aspects such as driving decisions and safety at traffic light intersections.
This research also contributes in a practical sense to the design of safe transportation systems. The results can be used to design and develop vehicle assistance technologies that target specific personalities. Furthermore, findings from this dissertation can be used in future research of machine learning and adaptive autonomous driving systems. Additionally, findings from this dissertation can be used to design driving safety courses and training programs that target people���s personalities and specific needs to help improve driving safety
In Tlilli, in Tlapalli ���The Black Ink, The Red Ink���: Indigenous Experiences in Society and Healthcare from an Indigenous Philosophy
No full textThis dissertation consists of three articles that will address aspects of the Indigenous social and medical experience within United States society. Elevating Indigenous epistemologies and criticisms of standard epistemological traditions in concert with an Indigenous focused and crafted research method informs the overall methodology and analysis of the project. This focuses the paper to be an explicitly Indigenous focused research project created by an Indigenous person utilizing Indigenous millennia knowledge.
Indigenous peoples interact with healthcare systems just as much as any other social or ethnic group in the U.S., however they are unique since the U.S. government is obligated by treaty to provide healthcare for Indigenous communities through the Indian Health Service (IHS). Indigenous people are the only racialized ethnic group in the U.S. to be guaranteed such healthcare which creates a complex system where a colonial government and bureaucracy are directly responsible for some of the most important, sensitive, and life-threatening aspects of a racialized group���s lives. The first section will provide a discussion of the white racial framing and anti-Indigenous subframing of Indigenous people in the U.S. The second section will provide a brief tee-up for the third section by providing an overview and discussion of Indigenous history in the U.S., the scholarly defined eras of Indigenous history, and a comparison of Indigenous and Western bioethics. The final section will address how the history of anti-Indigenous framing has impacted the Indian Health Service and the federal government���s shocking mismanagement of the IHS, however it will also highlight how Indigenous nations are taking back their healthcare and fulfilling hard-fought principles of sovereignty
Semi-Synthetic Analogs of Occidiofungin
No full textFungal infections are a global healthcare concern. Multi-drug resistant fungal infections present a great challenge for the treatment of infected individuals. Current classes of antifungal agents each have their own limitations. The last class of antifungal agent approved for treating systemic fungal infection was echinocandins in the early 2000s. Occidiofungin is a natural product produced by the soil bacterium Burkholderia contaminans MS14. The structure is a cyclic glycolipopeptide consisting of 8 animo acids. The mechanism of action of occidiofungin is unique compared to current antifungal agents. Murine models demonstrated that occidiofungin had minimal toxicity and was effective in treating vulvovaginal candidiasis. Occidiofungin is currently in phase 1 clinical trials for the treatment of recurrent vulvovaginal candidiasis. This dissertation is focused on the characterization of novel occidiofungin variants, and the production and characterization of semi-synthetic occidiofungin analogs. Semi-synthetic occidiofungin analogs were produced by modifying the sidechain of novel amino acid 2. These analogs were used to investigate the structure-activity relationship of occidiofungin. The diol group on novel amino acid 2 plays an important role in the antifungal activity of occidiofungin, likely contributing to cellular uptake. A newly identified occidiofungin variant was identified which contains aspartic acid instead of asparagine at position 7. The aspartic acid variant could be utilized to produce semi-synthetic analogs by targeting the terminal carboxylic acid on the aspartic acid. The aspartic acid residue presents a region that is highly amenable to modification without reducing antifungal activity. A phosphate prodrug semi-synthetic analog designed to treat systemic infection has been developed. Occidiofungin was not able to reduce the fungal load in a systemic candidiasis murine model, which may be due to high levels of binding to serum proteins. The phosphate prodrug analog demonstrated in vitro antifungal activity and reduced binding to serum proteins. Future investigation into the efficacy of the phosphate prodrug analog in treating systemic fungal infections will be performed
Selective Modulation of Metal-Insulator Transitions Through Ion Irradiation and Ion Implantation for Neuromorphic Applications
No full textVanadium dioxide (VO2) is a strongly electronic correlated material that exhibits a metal insulator transition (MIT) at 68 ��C. The MIT can result in a up to four orders of magnitude change in electrical conductivity, which is coupled with a structural phase transition (SPT) where VO2 transforms from insulating monoclinic to metallic rutile. The nonlinear characteristics of charge transport related with this phase transition enable non-linear dynamical behavior that are of interest for neuromorphic computing applications.
Despite this interest, application of VO2 to devices and circuits for the purpose of emulating neuronal behavior is limited by 1) control over electrical transport behavior in the two phases, and 2) control over aspects of the structural transition itself, including the extent of phase coexistence. All these factors play a role in both emulating neuronal character and extending the lifetime of a VO2 memristor. Previous research has focused on either 1) chemical doping of VO2 2) use of strain via lattice mismatch and 3) creation of defects all to modify aspects of the transformation.
To address these challenges this work focuses on the intersecting effects of chemical doping, lattice strain, and irradiation induced defects on the electrical transport and neuronal oscillatory behavior of VO2. The main focus is to map material property changes to engineer nonlinear behavior in memristive devices. Chapter 2 and 3 first explore He+ irradiation as an effective method to selectively tune the �� of both phases without changing other aspects of the transformation. Chapter 4 explores trends between transport changes and electro-thermal oscillations by comparing pristine, He+ irradiated, and Ge+ implanted memristor devices
A State-of-the-Evidence Review: Impacts of Youth Agricultural Education Programs on Global Poverty, Resilience, and Food Security Results
No full textHistorically underestimated, youth can catalyze change towards positive community development. In developing countries, there is tremendous potential to engage youth, not only as passive participants in programming or as a vulnerable population in need of services, but as potential innovators, early adopters, and effective change agents towards the adoption of innovations to improve family and community well-being. However, the body of evidence exploring how youth agricultural education programs impact the necessary global goals of food security, resilience, and nutrition has yet to be systematically evaluated, synthesized, and mapped. This study, the first systematic review of youth agricultural education programs in low- and middle-income countries, employs a mixed methods, theory-based approach to identify evidence of program outcomes and impact, mapping the current state of the evidence to the U.S. Global Food Security Strategy results framework.
With the aim of greater policy and programmatic relevance, this study employs mixed methods theory-based systematic review methodology. The findings provide evidence of how access to information, innovations, and social systems through well-planned, and locally adapted agricultural education can have significant positive influence on individual and family-level changes. However, rigorous evaluation of the outcome and impact-level results of investments in agricultural education is woefully inadequate, and the majority of evaluations of youth agricultural education programs neglect to address dynamics of gender and social inclusion in the evaluation design or reporting. Going beyond the descriptive quantitative systematic review results with the aim of greater policy and programmatic relevance, this paper discusses the results of the qualitative analysis of the 79 included studies, identifying enablers and barriers to positive program outcomes in agricultural education programs, to summarize the individual-level, program-level, and enabling environment factors influencing program outcomes. Ultimately, the paper presents an emerging conceptual framework for the design of youth agricultural education programs in low- and middle-income countries. The detailed results of this study provide insight to build on what we know (scale what is working), improve what we are currently doing (drawing from the lessons learned), and invest in improved evaluation and measurement, presenting recommendations for future programs, policy, and research
Learning from Successful Qatari Women in Corporate Management: Stories of Career Development and Lived Experiences
No full textThe purpose of this study was to explore Qatari women���s career development journey to management within the context of Qatar���s unique culture, honoring ancient traditions while ambitiously entering modernity. For Qatari women to be equally represented in corporate management they must be motivated and aspire to compete for influential positions in gender-mixed environments. This study used a qualitative, life history approach to examine their life experiences that have influenced their career development, in gender-mixed work environments. A two-part data analysis approach was conducted consisting of (a) the construction of a case story that reflected the biographical, life history of each participant as it related to her career development, and (b) inductive, cross-case thematic analysis. The major themes that emerged from this process concerned the critical career development stages that contributed to the personal and professional growth of participants and had a direct impact on their career progression. The four major themes identified were: (a) early beginnings; (b) quest for higher education; (c) establishing and managing career; and (d) strategies for sustained career success.
The participants��� early beginnings centered around their family and were heavily influenced by their father���s support. The love and care shown by their families enabled them to adapt to strong guardianship by showing respect, honor, and obedience to their families. During their quest for higher education, participants were guided by their families��� expectations for educational attainment. They developed resilience in the face of challenges, which altered their original plans for university and caused them to pivot and reconstruct their vision for a university experience. Upon finishing university and entering the workforce, participants��� greatest challenge was assimilating into a gender-mixed work environment. In this new environment the women faced gender bias, ageism, and had to confront societal judgement, which had a strong presence in their work environments. The women worked hard to prove their professional credibility by developing their interpersonal skills and finding their professional voice. Predominant enablers of their success were having a high-risk, growth mindset, managing positive relationships with their supervisors and mentors, and finding a meaningful purpose to drive their ambition and success
Complex Fluids Formed from Surfactant-Based Dynamic Binary Complexes
No full textThis work attempts to study the rheological properties and corresponding morphologies associated with complex fluids formed by novel surfactant-based dynamic binary complexes. Dynamic binary complexes refer to non-covalent supramolecular assemblies of surfactants and an appropriate complexing agent, giving rise to the potential for stimuli-responsiveness. The fundamental mechanisms that constitute viscosity modifier systems are an important point of discussion as well. Such chemistries are capable of interesting nanoarchitectures in aqueous suspension, that can have wide-ranging implications in several multi-billion dollar industries such as pharmaceuticals, personal care and the energy sector.
We examined an aqueous system of zwitterionic surfactant stearyl betaine with diethylenetriamine as the complexing agent, which displayed pH-responsive rheological properties and morphological changes. The surfactant was synthesized via a straightforward condensation reaction and then mixed with diethylenetriamine in an aqueous suspension at 2wt% to formulate the system. Notably, acidic conditions exhibited substantial steady-shear viscosities (up to 160 Pa.s) and viscoelastic behavior, decreasing with rising pH. A temperature analysis using zero-shear viscosities and differential scanning calorimetry unveiled thermodynamic transitions. Morphological insights from AFM and SAXS revealed distinctive bilayer nanotubules at low pH, transforming into bilayer sheets and then vesicles with increasing pH.
We then studied a system comprising of ��-cyclodextrin (��-CD) with three sulfonic surfactants: sodium hexadecylsulfate, sodium dodecylbenzenesulfonate, and myristyl sulfobetaine. Optimal axial growth and high viscosities in the suspensions were achieved with a ��-CD:surfactant ratio of 2:1. The complexation processes exhibited nanostructural phase behaviors and rheological properties sensitive to the molecular structure of sulfonic surfactants. DIC microscopy provided visual insights into the microstructure regarding sulfonate molecular architecture. Additionally, surface tension measurements, along with FTIR and NMR spectroscopies, deepened the understanding of interactions leading to complexation and nanostructural features. The proposed mechanics aimed to correlate supramolecular morphologies with rheological properties
Ira Greenbaum field notebook: GK2001-GK2500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for GK2001-GK2500 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection