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Multiphysics Models to Predict the Peformance and Reliability of Electroadhesive Surface Haptic Devices
No full textHaptics refers to the sense of touch, and surface haptics is the branch of haptics that deals with the generation of tactile effects on touch surfaces to make user experiences more immersive and realistic. Electroadhesive surface haptic devices make use of electroadhesion to apply electrostatic forces at the human-device interface, which is then modulated to modulate the interfacial friction forces and generate tactile effects.
Devices that incorporate such state-of-the-art technology often face several reliability and performance issues in their nascent stages that need to be resolved to enable their successful commercialization. Predictive models play an important role in the development of such devices because they provide designers with efficient tools to explore a wide design space to find solutions, as opposed to relying on an inefficient and expensive trial-and-error approach. In this study, we investigate a few such challenges associated with electroadhesive haptic devices. We will identify the key mechanisms causing visible preferential deposition of fingerprint residue on specific regions of the surface of commercial electroadhesive haptic touchscreens and develop a multiphysics predictive model that can be used to explore solutions to tackle this issue. We will then develop a finger mechanics model that can predict the roughness perception produced by distributed haptic devices. This model will provide insights into which mechanics properties trigger the mechanoreceptors that contribute to roughness perception. Finally, we will develop a multiphysics model that couples the contact mechanics, capillary, and electrostatic phenomena at the interface and can provide fast and accurate predictions about the interfacial friction force ��� an important parameter than needs to be accurately represented to make correct predictions about the device performance. Together, these models will provide useful tools to haptic device designers to build better haptic devices in a quick and cost-effective way
Evaluating the Attentional Demand of Visual and Auditory Stimuli on Adolescents with ADHD Using a Dual Task Paradigm
No full textAttention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder defined by impaired levels of inattention and/or hyperactivity ��� characterized by being unable to stay focused in the face of distraction or think flexibly when presented more than one stimulus. This inability to remain focused may make it difficult to do two things at one time, or dual task.
Dual task is a paradigm used to quantify allocation of attention by asking subjects to perform two tasks consecutively and measuring the difference in their performance individually to completing them together. Usually done with walking and a cognitive task. The type of cognitive task may be important in ADHD because of poorer responses to visual vs auditory stimuli.
This study sought out to examine the difference in dual task cost (DTC) between auditory and visual stimuli-based tasks in older adolescents with ADHD tendencies. The hypothesis was people with ADHD tendencies would experience a higher DTC under visual than the auditory tasks.
Nineteen subjects completed five randomized, one-minute collections of single task (ST) walking, ST visual, ST auditory, dual task (DT) visual (walking while performing the test), and DT auditory. The cognitive DTC was calculated using the percent correct answer difference. The gait DTC was calculated for step width and gait speed. Both the signed and absolute DTC values were analyzed to examine both the direction of the cost as well as the magnitude of the change. Comparisons were made between visual and auditory DTC for percent correct, gait speed, and step width. The absolute value of the cognitive DTC was found to have significance (p<0.001), with the auditory having a higher magnitude of DTC than the visual. Other comparisons were not significant.
Little to no evidence was found to support the hypothesis. This was likely due to the use of preferred gait speed, which may not have challenged attentional resources. Further, it is feasible that there is a cognitive benefit of walking on working memory. Future studies should investigate or control for subtypes or comorbidities of ADHD, the mechanisms of auditory processing in those with ADHD, and the cognitive benefits associated with walking
How Are Standards Developed? An Analysis of the Science Standards Revision Process in Texas
No full textThis study aimed to determine how science education policy is developed and the expertise employed throughout the process. Texas was selected as a historical case due to the recent revision of the science standards, their large impact, and documentation availability. A historical perspective informed the research questions: 1) What are the key positions, underlying justifications, and factors that contributed to the development of science standards in the state of Texas? 2) What expertise do official and unofficial actors possess in the science standards revision process? 3) To what extent were Schwab���s commonplaces (subject matter, teachers, learners, and milieu) considered during the revision process for science standards? and 4) What is the State Board of Education review process followed when revising science standards? State Board of Education meetings were analyzed using naturalistic inquiry and within-case methods.
Findings indicate that several points of failure occurred throughout the revision process that may affect the viability and implementation of the resulting standards. These points of failure included flawed process design, transparency issues, and limited representation of expertise domains. Notably, the learner was not represented during the revision process. As a result, the standards risk being developmentally inappropriate for students; initial evidence suggests this is the case for several standards. To ensure standards are scientifically accurate, developmentally appropriate, can be implemented by teachers, and respectful of the environment in which it is enacted, expertise from the subject matter, the learner/learning, the teacher, and the milieu must be equally considered. Additionally, research, development, and diffusion (RD&D) should be utilized to ensure the standards and curriculum materials are appropriately tested before being required for teachers and students
Applying Topology-Based Machine Learning to Risk Stratification in Pulmonary Arterial Hypertension
No full textRisk assessment instruments such as REVEAL Lite 2 can identify patients at high risk for events related to Pulmonary Arterial Hypertension (PAH). However, some patients classified as low or intermediate risk can still experience disease-worsening events, suggesting that these patients are at increased risk beyond that specified by traditional risk stratification tools.
We utilized a dataset of 109 consecutive PAH patients seen between January 2016 and December 2019. PAH-related worsening events occurred in 22 patients. An event was defined as the initiation of parenteral prostacyclin, lung transplantation referral, or death. The 87 patients without an event were used as controls. Echocardiography and REVEAL Lite 2 variables were obtained 4-8 months prior to an event. Topological Data Analysis (TDA), a machine-learning method well-suited to finding hidden patterns in high-dimensional datasets, was used to analyze the dataset. The TDA results then guided Kolmogorov-Smirnov Two-Sample Tests to identify variables differentiating event-prone patients from low-event patients.
Kolmogorov-Smirnov Two Sample Testing of event-prone and low-event patients across all three risk levels showed REVEAL Lite 2 had a KS-Score of 0.303, putting it below echocardiographic variables such as end-systolic eccentricity index (0.625) in terms of differentiating between the two groups.
In this single center machine learning-based study, TDA was able to identify a unique phenotype of patients defined by worsened echocardiographic parameters who were at high-risk of PAH-related events even when deemed low-risk by traditional risk assessment scoring methods. Future risk stratification studies should consider TDA and other machine learning methods
The BAZ Family of Chromatin Remodelers in Colorectal Cancer: Insights into Oncogenesis, Alternative Splicing and Chemosensitization
No full textColorectal cancer (CRC) poses a significant healthcare challenge worldwide, necessitating a deeper understanding of the molecular mechanisms underlying its pathogenesis for improved therapeutic interventions. This thesis investigates the BAZ (Bromodomain Adjacent to Zinc finger) family of chromatin remodelers and their intricate involvement in CRC. The BAZ family members, including BAZ1A, BAZ1B, BAZ2A, and BAZ2B, exert critical regulatory functions in chromatin architecture and transcription, impacting various cellular processes from development to disease.
In colorectal cancer, BAZ1A is overexpressed, and its depletion resulted in diminished cell viability, increased apoptosis, augmented DNA damage, and cellular senescence, concomitant with the downregulation of components within the Wnt/��-catenin signaling pathway. In vivo studies corroborated these findings, revealing that knockdown of BAZ1A leads to diminished tumor growth and alterations in chromatin regulation. Interestingly, BAZ1A undergoes alternative splicing, which is promoted by treatment with histone deacetylase inhibitors, thereby highlighting its therapeutic potential. Remarkably, the full-length form of BAZ1A is implicated in DNA repair mechanisms, while its alternatively spliced counterpart is susceptible to increased DNA damage and sensitivity to DNA-damaging agents. These observations underscored the oncogenic role of BAZ1A in colorectal cancer and the importance of considering an oncogene���s alternative splicing patterns.
Similar to BAZ1A, BAZ2A is also upregulated in CRC and associated with reduced patient survival. Functional studies demonstrated their roles in inhibiting cell viability, colony formation, and modulating Wnt/��-catenin signaling. Inhibition of BAZ2A led to reduced tumor growth rates in mouse models, where it also affected histone modification patterns, favoring a less repressive chromatin state, and influencing major histocompatibility complex (MHC) regulation.
In contrast to BAZ1A and BAZ2A, BAZ1B knockdown enhanced cell viability, colony formation, and altered cell cycle progression, suggesting a tumor-suppressive role in metastatic CRC. BAZ1B impacted c-MYC expression independently of the Wnt/��-catenin pathway, and influenced p53 and p21 levels, implicating its involvement in tumor suppressive pathways.
Overall, the study underscores the potential of BAZ family members as therapeutic targets in CRC. Future research should focus on elucidating their molecular mechanisms, translating findings into clinical applications, and exploring combination therapies to improve treatment outcomes for CRC patients, thus advancing more personalized therapeutic approaches for CRC
Non-Destructive Viability Testing of Cotton Seeds Using Raman Spectroscopy and Optical Coherence Tomography
No full textIn recent years, the field of plant breeding has been quick to adopt new technologies for the analysis of field and crop systems, with optimistic results and massive quantities of data generated. In this thesis two such optical technologies, Raman spectroscopy and Optical Coherence Tomography (OCT), are used to produce quantifiable characteristics of cotton seed that may be used for analysis of viability and determination of the features that correlate to survivability. It was found that spatial variability of the Raman spectrum, as well as the occurrence or absence of specific delineations in the OCT tomograms correlate with seed viability.
Raman spectroscopy has proven to be an invaluable tool in the nondestructive analysis of biological materials. As it was previously found that fatty acid and carbohydrate content could be linked to seed viability, Raman signatures of these compounds are of particular interest. The ability of OCT to provide three-dimensional morphological structural details non-invasively, suggests its potential use for the analysis of internal seed structures. The features of interest include damage to the seed coat as well as clear demarcations in the seed interior, or subsurface features that could impact the germination of the seed. A comparison between the features documented by both technologies on each seed paired with a germination test allows correlations about the impacts that each feature and their combination have on the survivability of seeds.
We predict seed viability using the correlation of the observations we make in the Raman and OCT measurements with seed viability. With both cotton varieties (Tamcot 73 and G11) we find that when we select only seeds predicted to be viable, the germination rate is higher than for randomly selected control seeds. While the Tamcot 73 seeds we predicted to be viable germinated slightly better than the control seeds of the same variety, the overall low germination rate of these seeds indicates that other factors not measured by our techniques can have a large remaining impact. For the most recently harvested Tamcot G11 seeds, the germination rate of the control seeds was about 85%, leaving not much room for improvement, and thus a lower level of significance. The level of significance was highest for G11 seeds harvested in 2019, indicating that combined OCT and Raman measurements of seeds can be used to predict seed viability and to improve agronomic outcomes by selecting seeds with a higher expected chance to be germinating
John Bickham field notebook: Mamm_AK101-AK200.pdf
No full textEach page/AK number corresponds to a karyotype slide data and/or unique specimen.Data pages for Mamm_AK101-AK200 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
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
The Addition of Cyanoacrylate Adhesive to Knots of Various Suture Loops: A Study on Tensile Strength and Suture Loop Integrity
No full textCyanoacrylate adhesive is used by some practitioners in conjunction with sutures to secure free gingival grafts to a surgical bed, in conjunction with sutures to function as a dressing for palatal harvest sites or biopsy sites, or to help maintain primary closure with bone grafting procedures. There is limited research regarding the effects of cyanoacrylate adhesive on the mechanical properties of sutures in an oral environment. Therefore, the aim of this study is to determine whether or not the addition of cyanoacrylate adhesive to suture loops impacts suture maximum tensile strength or cause of suture failure under tension.
60 samples of each suture were tied around 5 PEX pipes using a three-throw surgeon���s knot. Cyanoacrylate adhesive was applied to half of the suture knots as per the manufacturer���s instructions. The rods containing the sutures were then immersed in an artificial saliva solution and the pH and temperature were monitored. 5 suture samples of each suture type from the cyanoacrylate group, and 5 sutures of each suture type from the non-cyanoacrylate group were tested for maximum tension at the following time points: prior to submersion, 24 hours post-submersion, 3 days post-submersion, 7 days post-submersion, 10 days post-submersions, and 14 days post-submersion. Maximum tensile strength, reason for suture failure, and location of suture failure were recorded.
PGA-PCL sutures showed a 37% incidence of knot slippage when cyanoacrylate was not added to the knot. The addition of cyanoacrylate resulted in a 0% incidence of knot slippage (p=0.0048). The cause of suture failure for PTFE was always knot slippage, regardless of the addition of cyanoacrylate. On the other hand, silk, polypropylene, chromic gut, and PGA loops always failed due to suture loop breakage, regardless of the addition of cyanoacrylate. The addition of cyanoacrylate resulted in a statistically significant difference in maximum tensile strength of monofilament sutures (p=0.00041), synthetic sutures (p=0.00018), and absorbable sutures (p=0.0000031). The adhesive also improved maximum tensile strength of suture loops for silk (p=0.00088), PTFE (p=0.0091), PGA (p=0.029), and PGA-PCL sutures (p=4.4E10������), but not for polypropylene (p=0.45) or chromic gut sutures (p=0.87). The effect of the addition of cyanoacrylate to PGA-PCL was statistically significantly different at all days, except for day 14 and the retentive effect of cyanoacrylate appeared to decrease with time.
The addition of cyanoacrylate adhesive eliminates knot slippage in PGA-PCL sutures and increases the maximum tensile strength of silk, PTFE, PGA, and PGA-PCL sutures. These findings suggest that the addition of cyanoacrylate adhesive to suture knots may enhance suture loop integrity in an oral environment
Innovative Fabrication of Asymmetric Mixed-Matrix Membranes for Gas Separation
No full textDespite extensive research on mixed-matrix membranes (MMMs), their path to commercial deployment has been obstructed by a range of scientific and engineering barriers. This study introduces a novel, one-step method for fabricating MMMs, promising to advance their commercialization by addressing many of these existing challenges. This method, known as phase-inversion in sync with metal-organic framework (MOF) formation (PIMOF), allows for the swift creation of high-performance, asymmetric MMMs on a scalable basis. It involves a polymer film undergoing phase inversion while ZIF-8 nanoparticles are simultaneously generated in-situ within the polymer matrix. The produced MMMs exhibit exceptional propylene/propane separation efficiency, largely owing to the high effective ZIF-8 loading and the augmented molecular sieving capability of the uniquely small sub-5 nm ZIF-8 filler nanoparticles, facilitated by restricted linker swing motion. Subsequently, our research delves into the impact of modulating ligands, sodium formate and 1,4-butanediol, on the development of ZIF-8 fillers within the polymer matrix, aiming to elevate the separation capabilities of asymmetric MMMs crafted via the PIMOF technique. Our computational analysis supplements this empirical research, examining how the size of ZIF-8 nanoparticles influences the specific surface interaction energy and the apertures of ZIF-8. The findings suggest that smaller ZIF-8 nanoparticles foster stronger interactions with the polymer, affecting the nanoparticle's aperture size. These advancements mark a significant leap forward, surpassing the performance of all previously documented propylene-selective MMMs. Lastly, a hybrid strategy that involves the mixing of metals and/or linkers has been explored to precisely adjust the porosity and surface characteristics of the ZIF framework, thereby broadening their utility in the separation of various critical gas mixtures. The technique of linker-doping, as detailed in this report, represents a viable approach to diversify the range of imidazolate linkers, enabling the creation of mixed-linker hybrid ZIFs. Specifically, the doping of 2-ethylimidazole (eIm) into the frameworks of ZIF-8 and ZIF-67 has been examined, demonstrating the potential of this innovative method to improve gas transport across the membranes. This approach not only illustrates the adaptability of ZIF materials to meet diverse separation needs but also highlights the potential for tailored membrane design to enhance separation performance