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Development and Characterization of Novel Extrusion-Based Bioprinting Techniques for Living Materials
No full textThis dissertation presents the development and characterization of novel extrusion-based bioprinting strategies for fabricating engineered living materials (ELMs) with enhanced mass transport and in situ functionalization. Two primary research directions are explored: (1) vascularized hydrogel scaffolds with embedded microtubes to address the challenge of nutrient diffusion in large tissue constructs, and (2) three-dimensional printing of bacterial cellulose (BC)-producing hydrogels to create self-reinforcing living materials.
The first part introduces a hybrid bioprinting method that integrates coaxial core–sheath electrospinning with extrusion-based hydrogel printing. Porous microtubes resembling capillary vessels are embedded within sodium alginate scaffolds, significantly enhancing internal mass transport under both passive and pressurized conditions. Diffusion tests, SEM–EDS imaging, and cell viability assays confirm the functionality and biocompatibility of the microtubes, resulting in a fourfold increase in cell survival in the scaffold core.
The second part focuses on the fabrication of BC-based living materials using Komagataeibacter xylinus embedded in partially crosslinked sodium alginate bioinks. A two-step bioprinting strategy was developed: pre-crosslinked SA forms the structural frame, while uncrosslinked bacteria-laden SA enables in situ cellulose synthesis. A full factorial design was used to investigate the effects of SA concentration and culture duration on cellulose yield, nanofiber structure, and mechanical properties. Results showed that lower SA concentrations favored BC formation, while 4% SA offered the optimal balance between printability and bacterial activity.
Rheological, printability, and tensile testing demonstrated the functional enhancement of hydrogel scaffolds via bacterial cellulose reinforcement. The final constructs exhibited high structural fidelity, biological activity, and mechanical tunability.
Overall, this work contributes scalable, minimal-component strategies for constructing vascularized and cellulose-reinforced ELMs, advancing the capabilities of microbial bioprinting for applications in tissue engineering, responsive biomaterials, and sustainable biofabrication
A History of the Woman's Missionary Society from 1902-1944.
No full textwritten and compiled by Mrs. J. H. Hankins, Historian, First Baptist Church, Lubbock, Texas
Ray, David B. III-107 HL 1417.
No full textMaterials related to Rev. William David Ray, pastor of First Baptist Church Lubbock c. 1960s
The effects of external stressors on aquatic macroinvertebrate communities in Texas
No full textFreshwater ecosystems support extraordinary biodiversity and provide essential ecosystem services, yet they face escalating threats such as habitat degradation, invasive species, and climate change. In regions like Texas, where natural hydrologic variability intersects with land-use change, understanding how aquatic communities respond to multiple stressors is critical for effective conservation. Aquatic macroinvertebrates represent key contributors to freshwater food webs and ecosystem functioning, so they are particularly sensitive to environmental disturbance and offer powerful indicators of ecological change. However, many macroinvertebrate taxa remain data deficient, complicating monitoring and management efforts. My dissertation investigates the impacts of data deficiency, biological invasions, and hydrologic variability on aquatic macroinvertebrate communities across Texas. Chapter II provides updated distribution and habitat data for the Kisatchie painted crayfish (Faxonius maletae), challenging its presumed status as “Data Deficient” and instead asserting that the species is rare and warrants conservation action. Chapter III evaluates how feral hog disturbance affects aquatic-terrestrial linkages and macroinvertebrate communities in a spring-fed river. Feral hogs exhibited localized impacts to water quality and specific indicator taxa, demonstrating the need for further research on the effects of terrestrial invasive species on aquatic ecosystems. Chapter IV uses a mesocosm experiment to examine whether functional traits better capture aquatic insect responses to drying conditions than taxonomy alone. Neither functional, nor taxonomic composition responded to hydrologic condition, but did show a change in composition over time. This study demonstrates the need for better tools to understand how ecological communities assemble over time. Collectively, these studies highlight the value of trait-based approaches and demonstrate how macroinvertebrate community composition can inform more targeted, ecologically grounded freshwater management strategies under growing environmental pressure
Optimizing the Energy Transfer of Pulse Transformers
No full textVarious pulse transformers were designed and tested for the purpose of quickly charging a capacitive load to a differential voltage of up to 100 kV. The first pulse charger was designed and tested to charge a 0.5 nF load to +/- 50 kV in less than 10 μs. This pulse charger was also designed to be modular, so multiple loads could be charged simultaneously. Changes to the pulse transformer design were then investigated to see what, if any, improvements could be made for the purposes of developing a pulse charger that could charge a coaxial cable up to 100 kV. Variations to the transformer core dimensions, winding configurations, and use of multiple transformers were tested and analyzed for potential benefits to step-up ratio and rise time. From this, a rack-mount pulse charger was designed and tested to charge a 20 ft DS-2121 cable up to 100 kV in less than 2 μs. Additionally, electromagnetic simulations of the pulse transformer were developed for the purposes of testing various other pulse transformer configurations for future pulse chargers. The investigation into utilizing pulse transformers for quickly and efficiently charging capacitive loads is key for compact pulse power systems that can be reliably used in more complex designs
Three Essays Exploring Household Investor Behavior in the Digital Finance Era
No full textDigital finance represents a paradigm shift in global economic systems driven by the convergence of decentralized technologies. These emerging technologies transcend traditional financial systems, enabling peer-to-peer transactions and democratized access to capital through blockchain, decentralized finance (DeFi), and tokenized assets. However, this transformation introduces new challenges: regulatory fragmentation, consumer vulnerabilities, and dilemmas in understanding household behaviors. The following three essays examine how digital finance redefines ownership, trust, and economic agency.
The first essay examines the association between investment fraud concerns and confidence in financial market regulation and the use of financial advisors in investment decision-making using 2021 National Financial Capability Study (NFCS) State by State and Investor Survey data. The study shares insights into how household investors navigate the challenge of balancing risk and trust when seeking professional financial advice.
The second essay uses 2021 State by State and Investor Survey NFCS data to investigate whether investment fraud concerns or regulatory trust is related to cryptocurrency investment decisions. The study highlights how these factors may either boost or weaken investor confidence and deter or attract potential retail investors.
In the third essay, I explore the role of mobile trading apps and investment knowledge in risky investment decisions using the 2021 NFCS State by State and Investor Survey datasets. The study highlights that user-friendly interfaces and gamification increase the propensity for high-risk trades, particularly among individuals with varying levels of financial knowledge
Unveiling the X-ray Source Population of the Barred Spiral Galaxy NGC 2336
No full textWe present a comprehensive study of the X-ray source population in the nearby spiral galaxy NGC 2336, based on nine Chandra observations spanning a 7-month period. A total of 32 X-ray sources were detected down to a limiting luminosity of ∼ 1.4 × 1038 erg s−1 in the 0.5–7.0 keV (broad) energy band. Five sources exhibit luminosities exceeding 1039 erg s−1 in the broad band in co-added dataset and are classified as ultra-luminous X-ray sources (ULXs). One ULX, with over 90 net counts in a single observation, was analyzed spectrally using an absorbed power-law model, yielding a photon index Γ ∼ 1.8 ± 0.3, consistent with typical ULX spectra. Though this source has been previously classified as a non-active Seyfert 2 nucleus, we refrain from a more detailed classification due to data limitations. Photometric properties were derived for all sources, and hardness ratio analysis revealed six hard sources, including two ULXs. Variability analysis using χ2 statistics identified 13 variable sources over the 7-month period. Eight sources varied in Period 1 (December 2020), and nine in Period 2 (July 2021), while all five ULXs showing long-term variability and two exhibiting mid-term variability. In addition, we identified 2 candidate transient sources: one showing transient behavior in the extended dataset (i.e., both Periods), and in Period 1, and another showing transient behavior only in the extended dataset. To explore possible associations with star- forming regions, we cross-matched the X-ray sources with 78 UV-bright star-forming knots identified from UVIT data. After accounting for chance coincidence via Monte Carlo simulations, nine X-ray sources were confidently associated with UV knots, two of which have hard spectra and are classified as candidate high-mass X-ray binaries (HMXBs). None of the ULXs were reliably associated with UV knots, suggesting a likely low-mass X-ray binary (LMXB) origin. Notably, we identify a candidate transient ULX–LMXB system, a rare class of objects warranting further investigation. Future work will focus on the short-term variability of these sources assessed within each single observation and the analysis of archival HST data to provide detailed optical photometric characterization. This will enable a more complete census of massive star clusters and improved age and metallicity estimates via multi-wavelength stellar population modeling
Modeling the Fate of Oxidized Volatile Methylsiloxanes
No full textKelsey M. Stocker, Suffolk University, United StatesICES300: ECLSS Modeling and Test CorrelationsThe 54th International Conference on Environmental Systems was held in Prague, Czechia, on 13 July 2025 through 17 July 2025.Volatile methylsiloxanes (VMS) are known contaminants in
the International Space Station (ISS). VMS have been
detected in the gas phase, while some oxidized VMS such as
dimethylsilanediol (DMSD) are found in the aqueous phase.
Recent analyses have indicated that semivolatile or
nonvolatile VMS oxidation products may form organic
aerosols. In this work, the removal efficiency of oxidized
VMS via various routes on the ISS is modeled in order to
shed light on the potential for organic aerosol formation.
Results based on estimated physical properties indicate
that more than two sequential oxidations of a VMS lead to
complete removal via humidity condensate. Partially
oxidized VMS are also predicted to moderately partition to
the airborne particle phase. VMS with one or two oxidations
can thus be expected to play the largest role in aerosol
formation as they are not efficiently removed via humidity
condensate and may have a longer lifetime in the
environment
Continued Development of Advanced Sorbents for Improved RCA Performance
No full textAlex Wickham, Reaction Systems Inc, United StatesDavid Wickham, Reaction Systems Inc, United StatesMaggie Hurst, Reaction Systems Inc, United StatesZack Blanchette, Reaction Systems Inc, United StatesLawrence Barrett, Amentum JETS II, United StatesCinda Chullen, NASA Johnson Space Center (JSC), United StatesICES402: Extravehicular Activity: PLSS SystemsThe 54th International Conference on Environmental Systems was held in Prague, Czechia, on 13 July 2025 through 17 July 2025.NASA has a strong interest in improving the method to
control carbon dioxide (CO2) and humidity in the
Exploration Extravehicular Mobility Unit (xEMU).
Historically, the Metox has been used to remove CO2 from
the Extravehicular Mobility Unit (EMU). However, this unit
utilizes a solid silver oxide sorbent which has a finite
capacity and requires maintenance for thermal regeneration
between extravehicular activity (EVA) missions. The
technology currently planned to replace the Metox in the
xEMU is the Rapid Cycle Amine (RCA). This device utilizes a
regenerable, pressure swing adsorption system which
consists of two beds that alternate between adsorption of
CO2 and H2O and desorption of said compounds through
exposure to space vacuum. The RCA currently utilizes an
amine-based sorbent to perform this function designated as
SA9T. While this sorbent has significant reversible CO2
uptakes, an increase in these uptake capacities would
enable the reduction of the RCA mass, volume, and power
consumption while also enabling lower CO2 levels in the
xEMU. In addition, the current sorbent emits low levels of
ammonia, and a reduction of these emission levels is
desirable.
In an ongoing SBIR Phase II project, Reaction Systems
developed new sorbents that have the potential to improve
the performance of the RCA. Reaction Systems used a rapid
screening testing method along with its expertise in the
development of CO2 sorbents to identify several materials
that have potential to outperform SA9T. In this project,
Reaction Systems tested the performance of the sorbents
under realistic conditions using a twin bed CO2 control
module in a full-scale ventilation loop simulator and
characterized the sorbent cycle times as a function of CO2
partial pressure. The ammonia off gassing characteristics
of these sorbents were also characterized and they were
found to emit less ammonia than a sorbent that has a
similar composition as SA9T
Risk, Resilience, and Resources: Maternal Supportiveness and Family Resources and Their Impact on School Readiness Among Economically Disadvantaged Children in Latine Families
No full textThe transition to kindergarten is a critical developmental period in childhood. Although the link between supportive parental caregiving and income for child school readiness is well established, it remains relatively unknown how maternal supportiveness and family resources change over time to promote school readiness. Additionally, with a growing focus on a strengths-based approach to investigating Latine families, research in this area aims to better understand how the links between factors like caregiving and income, and later school readiness are mediated by child, parent, and family risk and resilience factors among Latine low-income families. The present study utilized latent growth curve modeling (LGCM) to investigate the longitudinal trajectories of maternal supportiveness and family resources across 14, 24, and 36 months and their direct and indirect effects on school readiness outcomes in Latine families. Using data from the Early Head Start Research and Evaluation Project (EHSREP), low-income, Latine families were extracted from the larger sample (N=486 families of mothers and children; 54% girls). The model revealed moderately high and increasing rates of family resources. Additionally, families demonstrated relatively high and stable levels of maternal supportiveness across time that did not vary across families. Strong associations between maternal supportiveness and family resources at 14 months and later school readiness outcomes were identified. Findings from this study could be informative for family policy makers and early childhood educators in how to best support low-income, Latine families in promoting family strengths that support the development of school readiness skills