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Understanding, Modeling, and Engineering Extracellular Electron Transfer in Lactic Acid Bacteria for Bioelectronic Sensing
No full textThe increasing demand for effective environmental monitoring and health diagnostics has spurred the development of fast, low-cost, and deployable sensing systems. A particularly promising technique is whole-cell bioelectronic sensors, which combine unique features of biology and electronics to convert chemical information into electrical signals via cellular electron transfer. In this thesis, I present the development of real-world deployable bioelectronic sensors based on probiotic lactic acid bacteria. To achieve this, I investigate novel electron transfer mechanisms in lactic acid bacteria and design modular engineering strategies to rewire these pathways for bioelectronic sensing. First, I uncover that the extracellular electron transfer (EET) pathway in Lactiplantibacillus plantarum interacts with diverse quinone electron mediators to generate electrical signals. Leveraging this phenomenon, I engineer synthetic microbial consortia where the EET activity of L. plantarum is activated by co-cultivated quinone-producing bacteria, such as Lactococcus lactis or Escherichia coli. By systematically dissecting the regulatory mechanism of quinone synthesis in the quinone-producing bacteria, I develop inducible genetic circuits to control quinone production. These genetic circuits enable the synthetic microbial consortia to detect diverse chemicals and subsequently activate quinone-mediated EET to produce electrical signals. Finally, I incorporate these engineered systems into miniature bioelectronic devices for portable, low-cost bioelectronic sensing in environmental, food, and human-relevant settings. Collectively, this thesis unlocks unprecedented applications of bioelectronic sensors and highlights how the convergence of synthetic biology, systems biology, material engineering, and electrical engineering can drive new strategies for creating biological-electronic hybrid systems
Food Insecurity in Houston and Harris County
Get PDFFood insecurity, or unreliable access to sufficient food and/or food of adequate quality, affects about 1 in 7 (14%) households nationally. In urban landscapes like Houston and Harris County, food insecurity is even more widespread, with clear disparities across households. In spring of 2024, over 5,200 members of the Greater Houston Community Panel (GHCP) reported on their challenges with food access, including the unaffordability of balanced or nutritious meals, skipping meals due to financial constraints, and hunger among adults and children. This report takes a closer look at the scope of food insecurity among households in Houston and Harris County
6.3 Community biology: Advancing responsible biotech innovation
Get PDFThis entreaty was created as part of The Spirit of Asilomar and the Future of Biotechnology summit (February 23-26, 2025) in Pacific Grove, CA.Community biology is a grassroots movement that can empower individuals and communities outside the traditional academic and industrial silos. It can offer local solutions to global challenges through community engagement and empowerment by establishing “third spaces” like community labs. These more accessible spaces can improve equity, resilience, and innovation with biotechnology that has already existed in local communities across the globe. To further illustrate its potential, compelling case studies of the diverse impact of community biology initiatives globally are provided. In this entreaty, we provide a call to action to support community biology globally by forging new partnerships, building needed infrastructure, and securing sources of funding. Recognizing community biology as essential infrastructure is paramount to ensuring that the benefits of biotechnology are realized by all
Teamwork Turbulence: Lessons for Multi-Team Systems from a Decade of Aviation Accident Reports
No full textEven in 2025, aviation accidents related to ineffective teamwork continue to be reported in the news, highlighting persistent challenges within the industry. Despite decades of
aviation safety and team science research, a critical gap remains in understanding one of the most complex aspects of aviation teaming—multi-team systems (MTSs). This work
aimed to address this research gap by investigating teamwork breakdowns within the aviation MTS. Through analyzing archival accident reports from the National Transportation Safety Board (NTSB) within the past decade, this research sought to
uncover the underlying causal factors that contribute to aviation accidents within the last decade (i.e., 2014-2024) using the Human Factors Analysis and Classification System
(HFACS; Wiegmann & Shappell, 2001). However, there is currently no comprehensive error framework specifically designed to analyze MTS-related attributes in aviation. While the HFACS framework does not explicitly focus on MTSs, it does identify teamwork as a personnel factor with the potential to contribute to human error. Therefore, this study explores whether MTS-specific errors can be classified through a proposed
theoretical extension of the HFACS framework. Accident reports related to teamwork dysfunction were further analyzed to understand and relate each event to MTS attributes
to more comprehensively understand the root of these teamwork breakdowns. Finally, this work uses insights from the analysis to propose theoretical implications to support
MTS safety and effectiveness
Optimization Algorithms for PDE-Constrained Optimization with Inexact Models
Get PDFThis thesis develops line-search algorithms that incorporate approximate objective function and gradient information to solve smooth optimization problems. These algorithms are motivated by the need to rigorously incorporate reduced order models (ROMs) into the solution of large-scale optimization problems governed by partial differential equations (PDEs). The developed algorithms are error-aware and update model error tolerances based on the progress of the optimization in order to reduce the accuracy requirements on the ROM approximations, and therefore the cost of ROM construction and evaluation. The algorithms require no explicit information about the underlying true model and operate entirely using error bounds on the objective and its gradient. In this work, previous approaches are extended to allow for more general classes of error bounds and to solve optimization problems with general nonlinear constraints. All algorithms are accompanied by proofs of first- order convergence. Numerical results show that the proposed line-search methods, combined with ROMs, converge to local minima of the original optimization problems more efficiently than approaches without ROM approximations
Optical, Electrical and Thermal Properties of Plasmonic Nanojunctions and Carbon Nanotube Fibers
No full textPlasmonic nanowires and nanojunctions with sub-nanometer gaps can be fabricated on chip in large scale and have exhibited potentials in applications in high sensitivity spectroscopy, single molecule, photoelectric and thermoelectric devices, and nanoscale light source in recent years. This thesis reviews the plasmonic behavior in plasmonic nanowires and nanojunctions and focuses on surface enhanced Raman spectroscopy (SERS) by remote excitation and nanojunction electroluminescence (EL) in magnetic field. Another project about probing the variation in the Seebeck coefficient in carbon nanotube fibers (CNTFs) using the photothermoelectric (PTE) effect is also discussed.
In Chapter 1, I will introduce some basic concepts including plasmons, Raman spectroscopy, thermoelectric effects and carbon nanotubes (CNTs). In Chapter 2, I will focus on the plasmonic and thermoelectric behaviors of metallic nanowire and nanojunction systems, including photothermoelectric effect, plasmonic heating, SERS, open circuit photovoltage (OCPV) and EL.
In Chapter 3, I will discuss the remote excitation SERS in plasmonic molecular junctions. Surface plasmon polaritons (SPPs) are excited at nearby gratings, propagate to the junction, and couple to the local nanogap plasmon modes. Like direct excitation, remote excitation of the nanogap can generate both SERS emission and OCPV. We compare the SERS intensity and the OCPV in both direct and remote illumination configurations. SERS spectra obtained by remote excitation are much more stable than those obtained through direct excitation when the photon count rates are comparable. By statistical analysis of 33 devices, the coupling efficiency of remote excitation is calculated to be around 10%, consistent with the simulated energy flow.
In Chapter 4, I will discuss the large magnetic field dependent electroluminescence in nonmagnetic plasmonic nanojunctions. We experimentally find that EL spectra of planar nonmagnetic plasmonic nanojunctions are quite sensitive to an external magnetic field, with changes in total emission at specific wavelengths up to tens of percent under the external magnetic field of a few Tesla, exceeding simple classical expectations by more than two orders of magnitude. The linear and circular polarization analysis of the emitted spectra shows profound changes that are asymmetric with external field direction. The dramatic changes in polarized spectra under external field indicates that the LSPRs can be modified by the external field. The inferred plasmonic DOS and effective temperatures of hot carrier under different external magnetic field are different, which further indicates the magnetic field dependent LSPRs. A quantum-corrected model (QCM) simulation is performed to compare with the experimental results.
In chapter 5, we develop a method to probe the variation of the Seebeck coefficient along CNTFs using the PTE effect. The photovoltage is measured as a function of position, and the laser induced temperature profile is obtained by a robust steady state thermal model. The Seebeck coefficient as a function of position along the fiber can be obtained from the measured, spatially mapped photovoltage and the temperature profile. We observe a correlation between the variation of the Seebeck coefficient and the shift of Raman modes, both related to the doping level and Fermi energy. We find the Seebeck coefficient fluctuation in the pristine fiber is due to the non-uniformity of the doping level and the Fermi energy. With an established model to correlate the thermoelectric response and the Fermi energy, our PTE-based method can probe the Fermi energy fluctuation along the fiber with the resolution better than 1 meV, which is far beyond the capability of the commercial Raman spectroscopy. This study shows a non-destructive method to quantify the uniformity of CNTFs at the micrometer scale, key for fabricating more uniform and higher quality CNTFs and generalizable to other conducting fiber systems.
In Chapter 6, we will discuss possible follow-up research based on these projects. The details of the optical measurement setups in Natelson lab are introduced in Appendices
Coffee & Quality Case Study #4: HAAM Social Services
No full textIn response to a survey of nonprofit organizations in the Greater Houston area, United Way of Greater Houston and the Kinder Institute for Urban Research are conducting a series of case studies as a part of United Way’s existing Coffee & Quality program. The goals of this initiative are to work with designated nonprofit organizations to 1) identify ways to build and bolster their current practices to further the use of the data they collect, 2) use the data to understand and improve program outcomes, and 3) elevate generalizable insights that can support the work of other nonprofits in the Houston area and beyond. This report details the fourth case study in the series, wherein United Way and the Kinder Institute collaborated with HAAM Social Services (formerly known as Humble Area Assistance Ministries), an agency that supports individuals in northeast Harris County and east Montgomery County across a number of domains, including basic needs (e.g., food pantry), education (e.g., certification and GED assistance referrals), and employment (e.g., interview coaching)
Healthcare Access and Equity
No full textThis dissertation presents three essays examining healthcare access and equity in developing contexts, with a focus on India. The first essay investigates patient behavior in hospital selection following the implementation of a universal insurance program, shedding light on factors influencing healthcare utilization patterns. The second essay evaluates the multifaceted impacts of a large-scale subsidized menstrual hygiene product distribution scheme on women's health outcomes and educational attainment. The final essay assesses the effects of a nutrition intervention program targeting adolescent girls on both educational performance and health indicators. Together, these studies contribute to our understanding of how targeted health interventions and policy changes can address disparities in healthcare access and improve overall well-being in resource-constrained settings
Valentina V. for harp, immersive electronics, and lighting
No full textValentina V. is an extended work for solo harp, immersive electroacoustic sound, and lighting, commissioned by Hope Cowan through a generous grant from the American Harp Society. The piece is inspired by my own musicological research into the medieval song “La harpe de melodie” and the provenance of the illuminated manuscript containing the song’s renowned pictographic musical score.
Valentina V. is conceived as a tragic monodrama in which the solo harpist adopts the persona of 14th-century noblewoman and virtuoso harpist Valentina Visconti (1371–1408). Research suggests that the medieval song “La harpe de melodie” by Jacob de Senleches — famous for its illuminated pictographic score — was likely composed as a vehicle to showcase Valentina’s prodigious musical talents. Married to the brother of the King of France, Valentina was eventually forced into exile after others at the royal court accused her of witchcraft. My piece presents an imagined scene near the end of Valentina’s life in which she is confined to her chamber with only her precious harp to confide in.
Cast in four movements played without pause, Valentina V. unfolds fantasia-like as its protagonist processes her grief through playing her beloved harp. Compositional materials are partly derived from “La harpe de melodie,” which is performed in full as the work’s penultimate movement. At other points in the piece, the song emerges in a fragmented, distorted, or embellished form, representing Valentina’s reminiscences as they are filtered through her fractured psyche
Advancing Biological Wastewater Treatment Resilience in Extreme Wet Weather Events
No full textWet weather events such as hurricanes, tropical storms and heavy precipitation are increasing in frequency and duration because of climate change. These events can overwhelm critical infrastructure such as Waste Resource Recovery Facilities (WRRFs), due to heavy flows and/or loads, also known as hydraulic overloading. Conventional WRRFs, which are predominantly suspended growth systems, are not well equipped to manage hydraulic overloading and may discharge partially treated or untreated wastewater into rivers, lakes, and other receiving water bodies. The high influx of influent can additionally lead to washout of the suspended biomass responsible for biological treatment in WRRFs. Biomass washout can disproportionally impact slow-growing microbial populations (e.g., nitrifiers) and thus result in a prolonged impact on nitrification and nitrogen removal processes. Biofilm-based attached growth treatment systems, such as moving bed bioreactor (MBBR) and membrane aerated bioreactor (MABR), have been proposed as a technology with the potential to improve the resiliency of WRRFs to wet weather events, by preventing biomass washout and protecting slow growing nitrifiers. This dissertation presents advancements in our understanding of how wet weather affects the resilience of biofilm-based wastewater treatment systems. The first objective of this research was to evaluate the impact hydraulic overloading due to wet weather on the immediate system function, nitrifier community composition and resilience of biofilm-based wastewater treatment systems. The next objective was to assess how wet weather disturbances will affect the biofilm system’s function, both in the long term and under real conditions. Given the potential benefits of biofilm-based wastewater treatment systems in maintaining function under wet weather events, finally, a community-wide resiliency analysis was conducted for historic and future wet weather scenarios.
The impact of wet weather events on the functional and microbial community resilience of biofilm-based wastewater treatment system was evaluated with replicate bench-scale MBBRs were challenged with three different wet weather disturbances. Results showed that the nitrifier community and biofilm system’s function, in terms of ammonia-N and soluble organic carbon removal, were resilient to the wet weather disturbances as they recovered to the baseline levels post disturbance within hours. This work demonstrated that hydraulic overloading and starvation disturbances during wet weather events do not negatively impact the treatment systems’ function, microbial community structure and nitrifier community composition. Next, the nitrification efficiency and nitrifier community were evaluated using a pilot-scale MABR, installed at a City of Houston WRRF, Houston, USA, with real influent wastewater. The pilot-scale MABR system exhibited increased nitrification efficiency and an increase in nitrifier gene abundance one month post high flow event. A biofilm detachment strategy using periodic hydraulic overloading was thus proposed to boost the efficiency of ammonia-N removal in a MABR systems struggling with nitrification. Compared to the existing air scouring procedures, this liquid scouring method was demonstrated to also require less energy.
Using the City of Houston as a case study, the performance and resilience of nine individual Houston WRRFs were analyzed for historic and future wet weather scenario to determine their impact on the community-wide resilience of the city. An outcome of this research was the opportunity to allow decision-makers to make strategic investments in WRRF infrastructure upgrades using biofilm systems and navigate tradeoffs with respect to resiliency and life cycle costs like capital investment and operating cost. Taken together, the results from the bench-scale, pilot-scale and community-scale studies of biofilm-based wastewater treatment systems advance the application of biofilm systems to improve the resilience of WRRFs to wet weather events