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John Bickham field notebook: AK26001-AK26500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for AK26501-AK27000 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
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
Structured MXene-Polymer Composites from Pickering Emulsion Templating
No full textStructured polymer composites have gained increasing attention due to their superior property enhancement (e.g., thermal, electrical conductivity) compared to their homogeneous counterparts, by designing the internal filler structures in the polymer matrix. The fabrication and design of structured polymer composites are still challenging and the common methods (e.g., solution casting, melt blending) have limited control over the internal filler structures. Pickering emulsion templating, in contrast, is an attractive approach to creating structured composites due to their well-defined interfaces, manageable structure and dimensions, and ease of scale-up. Among the common Pickering particles, MXenes are of great interest as they have the ability to not only stabilize emulsions but also introduce functional properties into structures, such as high electrical conductivity, high EMI shielding, and rapid radio frequency (RF) heating.
In this work, we focus on the development of MXene Pickering emulsions in diverse fluidfluid systems (e.g., oil-water and oil-oil) and their use as templates for fabrication of functional structured MXene-polymer composites. Pickering emulsions drive nanosheets to the fluid-fluid interfaces and subsequent localized polymerization creates diverse structured polymer composites (e.g., capsules, armored particles, and porous monoliths). The ability to access both aqueous and nonaqueous emulsion systems largely expands the possible polymer compositions. The MXene nanosheets are organized in these composites instead of being randomly distributed throughout. For instance, polymerization of the emulsion interfaces gives polymer shells with nanosheets embedded, polymerization of the dispersed phase gives polymer particles armored with nanosheets, and polymerization of the continuous phase gives porous monoliths with polymer struct and nanosheets coated pores. The incorporation of MXenes imparts functional properties into their structures for additional applications. For example, the MXene armored particles can be used as feedstock to fabricate segregated films for efficient EMI shielding applications at low MXene loadings due to the templated network within the polymers. MXene-polymer capsules and porous monoliths show excellent RF heating performance due to the highly locally conductive regions in these structures. The research work in this dissertation provides a simple platform to produce diverse structured MXene-polymer composites with well-controlled filler distribution, versatile compositions, and functional properties for potential advanced applications
Sensitivity Analysis and Evaluation of Enhanced Geothermal Systems (EGS): Integrating Subsurface Simulation, Economics and Case Studies
No full textGeothermal energy has the potential to become a significant contributor to the effort toward energy transition because it is environmentally benign (i.e., carbon-free), renewable, and practically inexhaustible if managed properly. Geothermal energy can be extracted from different geological formations, ranging from low-temperature ones occurring at shallow depths -- suitable for heating and cooling applications -- to high-temperature reservoirs deep at kilometer-scale depths for power generation.
This study focuses on the deep geothermal systems that are referred to as Enhanced Geothermal Systems, EGS. Energy recovery from EGS involves drilling deep injection and production wells to reach deep, generally low-permeability geologic strata, and hydraulically fracturing the high-temperature rocks while ensuring communication between injectors and producers. Cold water injected into the reservoir is heated by the hot rock with which it comes in contact and is then recovered as a high-temperature fluid (liquid and/or vapor) at the production wells. Appropriate management ensures the long-term viability of this of semi-closed loop system.
In this research, I investigated in detail the thermo-hydraulic behavior of EGS by modeling the transport of fluid and heat in the subsurface by means of numerical simulation using a scientific code. I first analyzed in detail the behavior and performance of a base case model involving a representative (realistic) EGS reservoir. I then conducted (a) a thorough sensitivity analysis by varying key reservoir properties and operational practices that control/affect the behavior of the system and its efficiency, as well as (b) a techno-economic analysis based on the results of the numerical investigation studies. With the insight gained from the base and the sensitivity analysis studies, I investigated the feasibility and performance of a geothermal system at the RELLIS campus of Texas A&M University using existing data derived from earlier oil and gas recovery operations at the site. Finally, I include in this dissertation a full field-scale analysis of a geothermal system that I performed as part of an internship project at SLB (previously known as Schlumberger), an oilfield services company.
The main finding of the study is the importance of a heat-exchange surface area in the reservoir that is sufficiently large to enable (a) a high temperature of the recovered water, (b) a large flow rate (i.e., higher injection/production rates), and (c) mitigation and minimization of the inevitable thermal decline caused by the mining of heat by the injected cold water. Water (H2O) is shown to be consistently superior to supercritical CO2 (sCO2) as the heat-exchange (working) fluid, despite some thermophysical properties that appear to make sCO2 a promising candidate. The techno-economical analysis shows that drilling is the main factor increasing the cost of EGS. Thus, significant improvements in drilling efficiency and technologies are necessary to reduce the levelized cost of energy (LCOE) of EGS and make it an attractive energy recovery option
Modulating the Tumor Microenvironment via Plga-Mno2 Nanoparticle Mediated Hypoxia Reduction Leads to Increased Immune Responses Against Bone Metastases
No full textBone metastases result in a stark decrease in survivability in cancer cases, with most treatment options focusing on palliative care. Newer therapies, such as immunotherapies, use the patient���s immune cells to target tumors, sometimes to great effect. Though immunotherapies have been effective against some advanced-stage tumors, there has been limited success with bone metastases. Persistent hypoxia in the bone, necessary to maintain the hematopoietic stem cells, induces an immunosuppressive microenvironment that blunts the activity of cytotoxic immune cells against bone metastases. To address this, we have developed a nanoparticle capable of modulating the bone metastasis microenvironment to improve the antitumoral immune response. In this study, we use manganese dioxide nanoparticles (MnO2 NP) to catalyze the degradation of tumor-produced hydrogen peroxide, thereby generating oxygen. For improved biocompatibility and modulation of oxygen production, the MnO2 NPs were encapsulated into poly lactic-co-glycolic acid (PLGA-MnO2 NPs) to produce particles provide sustained high oxygen tension. The PLGA-MnO2 NPs were biocompatible, reduced hypoxia after penetration into the core of cancer spheroids, and decreased hypoxia-induced factor 1 alpha expression. Reducing hypoxia in the spheroid resulted in a decrease in adenosine, and lactate, immunosuppressive metabolites. Notably, the spheroids��� microenvironment changes enhanced NK cells' cytotoxicity, which obliterated the spheroids. Then, to address chronic hypoxia, we then developed altered the PLGA formulation to create poly lactic(50)-co-glycolic(50) (50:50 PLGA), poly lactic(75)-co-glycolic(25) (75:25 PLGA) and poly lactic acid (PLA) encapsulated MnO2 NPs. We then analyzed the oxygen kinetics due to each polymer type and showed that the 50:50 PLGA-MnO2 NPs exhibited the best short- and long-term control of hypoxia in cancer spheroids and the PLA-MnO2 NPs possessing the slowest O2 generation kinetics. In vivo, the 50:50 PLGA-MnO2 showed greater accumulation in the long bones and pelvis, common sites for bone metastases. The NPs decreased hypoxia in bone metastases and decreased regulatory T cell levels, resulting in enhanced survival of mice with established bone metastases
Estimation of Evapotranspiration Using Remote Sensing Data and Sebal Model in Adana, Turkiye
No full textThe world's population has been steadily increasing in recent decades, resulting in a higher demand for water. This demand, combined with the effects of climate change and the depletion of natural resources, has made it crucial to monitor water resources. Agriculture is the largest user of water, and its impact on water usage is becoming a growing concern. Evapotranspiration, which is the combined loss of water through evaporation and plant transpiration, plays a crucial role in the water budget and energy balance. This study examined the use of the python SEBAL (PySEBAL) model for estimating evapotranspiration in agricultural areas by utilizing Landsat satellite imagery and meteorological data. The research centered on Seyhan Plain, Adana, Turkey, from 2017 to 2019 and analyzed both summer and winter seasons across five different crop types: cotton, wheat, corn, soybean, and citrus. The PySEBAL model generated daily actual evapotranspiration maps at 30m resolution for the study area. Analysis of R-square values across years and crops revealed positive correlations, particularly for cotton (R-square = 0.819) and wheat (R-square = 0.809). Corn and citrus also showed positive correlations (R-square = 0.736 and 0.708, respectively), while soybean2 displayed a weaker association (R-square = 0.481). These findings suggest that the PySEBAL model can accurately predict Penman-Monteith evapotranspiration (PM-ET) for some crops (cotton, wheat) compared to others (soybean-2). The results indicated an overestimation of ET by the model compared to literature values. However, a positive correlation was found between PySEBAL-ET and Penman-Monteith evapotranspiration (PM-ET) estimates across all crops and years, suggesting the potential of SEBAL for agricultural water resource monitoring
Statewide 2023 Air Emission Calculations from Wind and Other Renewables VOL II
No full textA technical appendix for the volume I report to the Texas Commission on Environmental Quality For the Period January 2023 ��� December 2023
Border Commuting Student Experiences: Developing Transborder/Transfronterize Identities
No full textOscar Martinez argues that an international border is a ���line that separates one nation from another��� to keep the people in the poor country out of the rich country (1994:5). Border commuters cross international borders daily/weekly and participate in each country's society, straddling both physical and non-physical boundaries in the borderlands (Anzaldua 1987; Carter 2006). This thesis focuses on the identity development of high school border commuters, referred to as transfronterize/transborder students (Stephen 2007; Iglesias-Prieto 2011). In addition to the analysis of transborder complex identities and Prudence Carter���s (2006) concept of student ���boundary straddling,��� this study uses Falc��n Orta & Orta Falc��n���s (2018) Transborder Identity Formation Framework to examine how the experiences of border commuter high school students develop transfronterize/transborder identities. The guiding question in this study is: ���In what ways does border commuting for educational purposes shape the identity development of high school transborder/transfronterize students?��� Two specifying questions follow: ���How well do Falcon Orta and Orta Falcon���s Identity Formation Framework apply to transborder high school students?��� and ���How are the identity development experiences of high school transborder students similar/different to that of transborder college students based on the existing theory?��� To answer these questions, qualitative methods were used to explore transborder students��� self-perception, educational aspirations, and border commuting experiences. The findings indicate that the existing framework for transborder college students applies to the experiences of transborder high school students; however, younger students have influential factors that do not apply to college students and vice versa in developing their complex transborder identities
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
Experimental Demonstration of Multiport Multifrequency Power Systems
No full textWith considerable improvement on renewable energy and energy storage has been made, the use of renewable power sources and energy storage devices in the power system and the electrification of transportation are becoming a growing trend in recent years. To meet this need, increasing numbers of power electronics converters are included in these systems, which makes these systems become power electronics rich. In these power electronics rich systems, the interaction among the converters is significantly complicated and thus makes the power flow management challenging. The integration of these power electronics converters could be an appropriate solution to simplify the power flow management and enhance the controllability of the system.
In this research, a novel multiport multi-frequency power transfer system is presented. In this system, several independent virtual power flow channels could be established by introducing different switching frequencies in the power electronics converters. Virtual power isolation among the power flow channels could be built up because of orthogonality of the waveform. Hence, the virtual power flow channels in different frequencies will not interfere with each other. Bidirectional Power flow could happen between each port of the system, and they won���t interfere with each other.
In this research, a prototype multiport multi-frequency circuit based on the proposed theory is built up in the lab. Simulations and experiments with several scenarios are conducted. The basic operation of the prototype circuit is analyzed. And the performance of the simulations and experiments will be investigated and discussed. The feasibility of the multiport multi-frequency power transfer is validated by both simulations and experiments