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An Energy-Efficient Power Management Unit with Continuous MPPT for Magnetoelectrically Powered mm-Scale Bio-Implants
No full textImplantable medical devices (IMDs) offer transformative tools to substantially improve medical outcomes for cardiovascular diseases, pain relief, and neurological disorders. To realize minimally invasive implants with miniaturized volume and weight, wireless power transfer (WPT) has been extensively studied to replace bulky batteries that dominate the volume of traditional IMDs and require surgical replacements. Ultrasonic (US) and magneto-acoustic-electrical (ME) WPT modalities, which leverage low-frequency acoustic waves for energy transduction, become viable solutions for mm-scale receivers. Due to the higher impedance and stronger electromechanical coupling of these transducers, PMUs developed for inductive WPT and piezoelectric energy harvesting are not directly applicable, and recently demonstrated ME/US IMDs only adopt basic rectifier-(DCDC)-LDO PMU topologies. However, the basic PMUs exhibit critical limitations in efficiency and reliability, which motivates us to develop PMUs specifically for ME/US WPT.
This work presents a fully integrated PMU for ME WPT in miniaturized IMDs. It achieves load-independent maximum power extraction and usage by continuously matching the transducer’s impedance, dynamically optimizing the power stage across varying input/load conditions, and reusing the storage energy to sustain the system when input power drops. With the proposed Skewed-Duty MPPT technique and regulation efficiency optimizer, the system achieves a peak MPPT efficiency of 98.5% and a peak system overall efficiency of 73.33%
Trophic transmission of marine microbes in coastal marine systems
No full textMicrobiomes – complex communities of bacteria, viruses, fungi, and symbionts – are essential to host health and resilience against environmental stressors. These microbial communities are dynamic, often shifting throughout a host’s lifetime, making the transmission and accessibility of beneficial microbes a critical area of interest. Trophic transmission plays a key role in shaping microbiomes by facilitating the movement of microbes across food webs, particularly in coastal marine systems where corals depend on symbiotic relationships. To expand our understanding of trophic transmission in coastal marine systems, I examined the marine bacterial and coral-associated algal symbiont communities present in the feces of reef fishes and invertebrates across geographically and ecologically distinct reef systems. In Chapter 1, I investigated bacterial communities in the feces of 19 reef fish families spanning a range of trophic levels across the Japanese archipelago. My findings revealed significant differences in microbial composition across both fish families and foraging groups, with many bacteria providing beneficial ecosystem services, however, other abundant taxa are opportunistic pathogens that are associated with facilitating coral stress and mortality. In Chapter 2, I studied coral-associated algal symbionts (Family Symbiodiniaceae) in the feces of six Caribbean reef fish species to better understand the role of trophic interactions in symbiont transmission. I found that feces from corallivore and herbivore/detritivore foraging groups serve as an environmental hotspot for viable Symbiodiniaceae, sharing genera with the dominant hard corals in U.S. Virgin Island reef systems. In Chapter 3, I expanded the scope of trophic transmission to invertebrates by analyzing the densities of algal symbionts in the feces of the fireworm Hermodice carunculata in the Flower Garden Banks, a high coral cover reef in the northwest Gulf of Mexico. I found that fireworm feces represent an additional environmental reservoir of viable algal symbionts, and given the species’ proximity to coral substrates, is likely to play a direct role in symbiont delivery to coral collectives. My investigation of trophic transmission in coastal reef ecosystems highlights the role of consumer feces as a critical and underappreciated source of marine bacteria and coral-associated symbionts in reef ecosystems. Collectively, my research underscores the ecological importance of trophic transmission in coastal reef ecosystems and informs future monitoring of microbes in the face of global change
Energy Storage Devices: Performance and Regeneration
No full textThis thesis presents a deep understanding of a layered material,
Chromium Germanium Telluride (CrGeTe3) as a potential electrode material for energy storage devices. We conclude that CrGeTe3 crystals possess the ability to intercalate lithium ions with a high specific discharge capacity of 537.5 mAh/g. We also investigate the direct regeneration of degraded graphite anode by washing it with various organic solvents under different temperatures. We successfully revived the spent graphite from a specific capacity of 188.23 mAh/g
to 224.66 mAh/g at 0.02 C rate and from 41.53 mAh/g to 157.36 mAh/g at 0.1 C rate, by washing with a solution of iodine in ethanol. Washing in anhydrous acetonitrile at 50 °C also restores the capacity of spent graphite to 226.5 mAh/g at 0.02 C rate. Washing the spent graphite in acetonitrile containing 0.5% water
content at 70 °C exhibited a high restored specific capacity of 215.9 mAh/g at 0.02 C rate and 168.36 mAh/g at 0.1 C rate. These results pave way for ecofriendly full-body regeneration of lithium-ion batteries
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No full textThe EGS Collab project: Outcomes and lessons learned from hydraulic fracture stimulations in crystalline rock at 1.25 and 1.5 km depth
No full textWith the goal of better understanding stimulation in crystalline rock for improving enhanced geothermal systems (EGS), the EGS Collab Project performed a series of stimulations and flow tests at 1.25 and 1.5 km depths. The tests were performed in two well-instrumented testbeds in the Sanford Underground Research Facility in Lead, South Dakota, United States. The testbed for Experiment 1 at 1.5 km depth contained two open wells for injection and production and six instrumented monitoring wells surrounding the targeted stimulation zone. Four multi-step stimulation tests targeting hydraulic fracturing and nearly year-long ambient temperature and chilled water flow tests were performed in Experiment 1. The testbed for Experiments 2 and 3 was at 1.25 km depth and contained five open wells in an outwardly fanning five-spot pattern and two fans of well-instrumented monitoring wells surrounding the targeted stimulation zone. Experiment 2 targeted shear stimulation, and Experiment 3 targeted low-flow, high-flow, and oscillating pressure stimulation strategies. Hydraulic fracturing was successful in Experiments 1 and 3 in generating a connected system wherein injected water could be collected. However, the resulting flow was distributed dynamically, and not entirely collected at the anticipated production well. Thermal breakthrough was not observed in the production well, but that could have been masked by the Joule-Thomson effect. Shear stimulation in Experiment 2 did not occur – despite attempting to pressurize the fractures most likely to shear – because of the inability to inject water into a mostly-healed fracture, and the low shear-to-normal stress ratio. The EGS Collab experiments are described to provide a background for lessons learned on topics including induced seismicity, the correlation between seismicity and permeability, distributed and dynamic flow systems, thermoelastic and pressure effects, shear stimulation, local geology, thermal breakthrough, monitoring stimulation, grouting boreholes, modeling, and system management
Developing Fast and Accurate Arrhythmia Multi-label Detection Algorithm for Real-world ECG Monitoring
No full textArrhythmia detection is challenging due to the imbalance between normal and arrhythmia heartbeats, compounded by environmental noise in wearable devices compared to clinical settings. We propose a novel hierarchical model using CNN+BiLSTM with Attention for arrhythmia detection, featuring a binary classification for normal vs. arrhythmia beats and a multi-label classification for various arrhythmia types. We evaluated our model against several baselines on a proprietary dataset. Our model achieved 95% accuracy, 0.838 F1-score, and 0.906 AUC for binary classification, and 88% accuracy, 0.736 F1-score, and 0.875 AUC for multi-label classification, outperforming existing methods
Structure and Dilatational Response of Asphaltenes with Varying Solvent Quality
No full textDefined by their solubility class, asphaltenes represent the most polar, aromatic, and heaviest fraction of crude oil. They strongly adsorb at oil-water interfaces, forming viscoelastic films that confer solid-like mechanical properties that stabilize crude oil emulsions. It is suggested that asphaltenes form the most stable crude oil emulsions close to the onset point of precipitation, in which soluble and insoluble asphaltene nanoaggregates are in solution. The formation of these emulsions leads to undesired flow assurance problems for the oil and gas industry that require demulsification to prevent operational challenges and costs. Given the heterogeneity in chemical composition, structure, and molecular weight of natural asphaltenes, it remains challenging to identify how their aggregation, precipitation, and diffusion behavior at oil-water interfaces promote stability. We use small-angle X-ray scattering (SAXS)
and the oscillating pendant drop method to address this challenge and investigate the structure, aggregation behavior, and the dilatational rheology of asphaltenes and asphaltene-model molecule violanthrone-79 (VO-79) with decreasing solvent quality. We observed that the radius of gyration (Rg) is independent of solvent quality before the onset point of precipitation and decreases as solvent quality decreases. In addition, our results show that the complex dilatational modulus of soluble asphaltene nanoaggregates depends on the solvent quality and increases with aging. On the contrary, the interfacial dilatational response of VO-79 remains relatively constant with increasing aging and decreasing solvent quality. We hypothesize that soluble asphaltene nanoaggregates may be re-arranging at the oil-water interface due to their dispersed nature, thus influencing their packing and enhancing the mechanical proper-
ties of the asphaltene-stabilized interfacial film, thereby promoting emulsion stability. The direct connection between structure and the dilatational response of oil-water
interfaces stabilized by soluble asphaltenes is essential for understanding their interfacial properties and their role in the emulsification process near the onset point of precipitation. Understanding the relationship between the structural and interfacial features of soluble asphaltenes provides insights into developing effective demulsification strategies to prevent flow assurance issues associated with asphaltene-stabilized crude oil emulsions. Additionally, this work demonstrates feasibility in emulsion-based industrial applications
Pseudomonas aeruginosa Strategies in Infections and Intraspecies Competition
No full textPseudomonas aeruginosa is a Gram-negative, opportunistic human pathogen responsible for a variety of nosocomial infections, including bloodstream infections, ventilator-associated pneumonia, and urinary tract infections. These infections pose significant challenges in healthcare settings due to P. aeruginosa’s ability to gradually develop resistance to a wide range of antibiotics, including β-lactams, aminoglycosides, and fluoroquinolones. Consequently, understanding the mechanisms of P. aeruginosa infections is crucial for developing new modalities treatments, such as antivirulence therapy. A key aspect of its pathogenicity lies in the production of numerous virulence factors, including exotoxins, proteases, and quorum-sensing molecules, which enable it to damage host tissues and evade the immune system. Additionally, P. aeruginosa exhibits a remarkable ability to adapt to polymicrobial environments, often outcompeting other microorganisms by utilizing several secretion systems or quorum sensing systems to gain a fitness advantage. This adaptability not only enhances its survival but also makes it a formidable pathogen in chronic infections, particularly in immunocompromised patients.
Here we demonstrated that a class of glycolipids called rhamnolipids predominantly drive P. aeruginosa acute virulence against murine macrophages. Secreted rhamnolipids can form micelles that exhibit acute cytotoxicity, rupturing the macrophage plasma membrane and damaging intracellular organellar membranes within minutes. We also examine these rhamnolipid micelles’ structural and biochemical properties via transmission electron microscopy and liquid chromatography-mass spectrometry. While these micelles are particularly toxic to macrophages, they are also capable of damaging a wide range of other cells, including human bronchial epithelial cells, red blood cells, and even Gram-positive bacteria. Finally, we reported that rhamnolipid production in various panels of clinical isolates strongly correlates with P. aeruginosa virulence.
In addition, we also examined the consequences of pyoverdine production during P. aeruginosa lung infection, using an adapted in vitro pyoverdine virulence model in human bronchial epithelial cells (16HBE). Conditioned medium from P. aeruginosa caused acute cell death and severe damage to the epithelial monolayer in a pyoverdine-, but not pyochelin-, dependent manner. Interestingly, pyoverdine production is associated with secretion of cytotoxic rhamnolipids. Consistent with this observation, chemical depletion of lipids or genetic disruption of rhamnolipid production was sufficient to abrogate toxicity from conditioned medium on 16HBE cells. Altogether, these findings suggest that pyoverdine and pyochelin play distinct roles in virulence during acute P. aeruginosa lung infections.
In terms of intraspecies competition strategies employed by P. aeruginosa, we used a genome-wide transposon insertion library screen to discover that ST111 strains outcompete multiple non-ST111 strains through production of R pyocin. We confirmed this finding by showing that competitive dominance in vitro was lost by ST111 mutants with R pyocin gene deletions. Further investigation showed that sensitivity to ST111 R pyocins (specifically R5 pyocin) and R1 pyocins is caused by deficiency in the O-antigen ligase waaL, which leaves lipopolysaccharide (LPS) bereft of O antigen, enabling pyocins to bind the LPS core. Analysis of 5,135 typed P. aeruginosa strains revealed that majority of international, high-risk sequence types (including ST111, ST175, and ST235) are enriched for R5 pyocin production, indicating a correlation between these phenotypes and suggesting a novel approach for evaluating risk from emerging prevalent P. aeruginosa strains. Overall, our study sheds light on the mechanisms underlying the dominance of ST111 strains, highlighting the role of waaL in R pyocin susceptibility
Navigating AI in Education: Opportunities and Challenges in the Classroom
No full textSlides for graduate pedagogy workshop serie
Motional Dynamics in Trapped Ions and Rydberg Atoms, and Hybrid Quantum Algorithm for Classical Optimization
No full textQuantum information science has emerged as one of the most promising fields in contemporary research, relying on both software and hardware innovations. This thesis looks for both algorithms with quantum features that provide advantages over classical algorithms, and better hardware platforms for experiments and quantum computing. The work spans theoretical studies in both algorithm and hardware design, including hybrid quantum-classical algorithms and the development of quantum information processing platforms.
The algorithmic part has focused on the performance of a hybrid quantum algorithm - the Grover Quantum Approximate Optimization Algorithm (Grover QAOA) - designed for problems with multiple solutions. In practice, we find its potential for speedup in solution search and its ability to find all solutions. Furthermore, we propose a simplified protocol that reduces the classical complexity of optimizing the algorithm’s parameters, enhancing its practicality for future applications. Our implementation of Grover QAOA for multiple combinatorial optimization problems on trapped-ion quantum computers demonstrates that the algorithm can fulfill its fair-sampling advantage even on noisy devices.
In the hardware part, we mainly explore how the motion of cold atoms can either be used to engineer interactions or lead to previously overlooked decoherence. The first hardware platform we discuss is trapped ions, where we focus on implementing individual addressing to natively simulate new types of many-body systems. Our proposal leverages the exceptional controllability of trapped ions to explore dynamical models such as topological pumping. The second hardware platform we study is Rydberg atom lattices, where we investigate the
decoherence processes introduced by atomic motion during dynamics. Using the numerical tool of discrete truncated Wigner approximation, we simulate the coupled dynamics of electronic and motional degrees of freedom, demonstrating that atom motion induced by strong van der Waals interactions in Rydberg atoms can lead to significant decoherence in analog simulation experiments.
We have also explored specialized topics involving other quantum hardware platforms. One area of study is the reduction of frequency crowding in superconducting circuit quantum
chips. By properly designing the frequencies for each transmon qubit, we can improve the manufacturing yield of collision-free processors. Another area focuses on the SU(N) Fermi-Hubbard models on alkaline-earth-metal optical lattice platforms. We have obtained the
phase diagram of unit-filling models with imbalanced spin flavors. This work aids future experiments in searching for potential ground states of the unit-filling SU(N) model