50107 research outputs found
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Cryogenic Radio Receivers for Superconducting Qubit Readout
No full textEngineering research in quantum computing is geared towards building a ”useful” quantum computer; usefulness here refers to the capability of solving computation problems that hold significant value in commercial applications, but are currently impossible to do in reasonable time-frames using classical algorithms. This is fundamentally a problem of scale – problems that can be solved by few-qubit processors can also be readily simulated by classical supercomputers in realistic time-frames, but as these problems grow in complexity, quantum computers are believed to be able to provide an exponential speedup over their classical counterparts, the so-called quantum advantage. However, scaling quantum computers presents many challenges due to the need to perform complex signal control and data processing at nanosecond time scales on fragile quantum systems that need stringent degrees of isolation from the environment for the computations to be carried out with high fidelity. Some of the most promising implementations of experimental-grade quantum computers are maintained in cryogenic environments due to the fact that at low enough temperatures noise processes due to random thermal excitations can be minimized. However, the control and measurement of quantum processors is currently done by systems at room temperature, whose connections to the cryogenic environment present thermal loading that will need to be addressed as these processors scale and their IO requirements to co-processors grow in complexity. As such, one possible path to scaling co-processing capabilities without compromising the quantum processor’s performance is the partial or complete integration of the co-processor in the cryo-environment. Several works describe systems that aim to do just that; and ”Cryo-CMOS” has become an important research subspace. This thesis aims to add to the current advancements in this field, specifically in the area of qubit measurements. It culminates in the implementation of a radio receiver that leverages the advantages of BiCMOS technology in cryo-environments to measure the state of a superconducting transmon-based qubit while strapped to a 4K stage in a dilution refrigerator. Critically, we demonstrate that low-noise amplification, down-conversion, and demodulation can all be done in the cryo-environment on a constrained power budget, with high fidelity comparable to a state-of-the-art (InP-HEMT LNA-based) qubit readout system, when preceded by a high-gain, quantum-noise-limited Josephson parametric amplifier.NSF (Grant Number: 1809114)
Google, LLCDoctor of Philosophy (Ph.D.
Characterization of the mycomembrane permeability barrier
No full textThe recalcitrance of Mycobacterium tuberculosis to antibiotic treatment has been broadly attributed to the impermeability of the organism’s outer mycomembrane. The mycomembrane is covered with long chain fatty acids that make the cell envelope extremely hydrophobic as well as other surface lipids and proteins. It is largely presumed that the mycomembrane is a key factor in cellular impermeability for many compounds. However, the evidence supporting this hypothesis has been indirect and/or reliant on bulk population measurements. In this work we utilized labeling methods via alkyne-azide cycloaddition to track small fluorescent molecule accumulation directly past the mycomembrane. We were also able to use a similar workflow via the previously developed the Peptidoglycan Accessibility Click-Mediated AssessmeNt (PAC-MAN) method to covalently trap azide-modified small molecules in the peptidoglycan cell wall of live mycobacteria, after they have traversed the mycomembrane. Using PAC-MAN we now show that the mycomembrane differentially restricts access of fluorophores and antibiotic derivatives through testing in M. tuberculosis and the model organism M. smegmatis. Mycomembranes of both M. tuberculosis and M. smegmatis discriminate between divergent classes of antibiotics as well as between antibiotics within a single family, the fluoroquinolones. By analyzing sub-populations of M. tuberculosis and M. smegmatis, we also found that some fluorophores and vancomycin are heterogeneously restricted by the mycomembrane. Our work has also confirmed increase in antibiotic activity alongside increased accumulation. Our data indicate that the mycomembrane is a molecule- and cell-specific barrier to antibiotic permeation.Doctor of Philosophy (Ph.D.
From Silence to Speech: Reducing Teacher Talk Time and Cultivating Student Participation Within Beginner-Level Chinese Language Learning
No full textThorough instruction from dedicated Chinese language teachers is an indispensable aspect of Chinese as a Foreign Language (CFL) learning. However, the continuous flow of teacher talk, which encompasses information conveyed in the classroom, such as context and vocabulary, often comes at the expense of student input. Such one-way communication from the teacher poses significant challenges and prevents proficiency enhancement opportunities for students. Recent research emphasizes the necessity of maintaining balanced discourse between teachers and students to empower learners. To address this issue and promote student participation, reducing teacher talk time (TTT) emerges as a compelling strategy.
This action research study investigates the dynamics of teacher talk and the transition from silence to active participation of students in a beginner-level Chinese language classroom at an American university. In order to determine the impact of reducing TTT on student participation and factors contributing to the increase or decrease of student talk time (STT) and TTT, this study utilizes an action research approach in order to document patterns of TTT and STT over the course of three cycles. Methods of data collection include self-assessments and action plans completed by the teacher; classroom and video observations conducted by both the teacher and an external observer; and questionnaires and interviews administered to students. The study proposes that by engaging in constant observation of classroom participation dynamics both individually and collaboratively in addition to understanding motives which prompt students to speak up, TTT can be minimized, facilitating opportunities for student expression. Conversely, excessive teacher talk will inhibit student engagement and limit authentic communication opportunities in the CFL classroom.
The results aim to shed light on the actual distribution of TTT and STT in the classroom alongside its associated factors, revealing that both the teacher’s and students’ perception of these dynamics does not always align with reality. A quantitative comparison across the cycles showed a 20.8% decrease in TTT and a corresponding 20.1% increase in STT from the first to the third cycle. However, the analysis indicates that this relationship is not always straightforward. The shifts in TTT and STT are shaped by multiple variables, including teacher adaptability, student confidence and anxiety levels, the classroom environment, the presence of meaningful speaking opportunities which include pair and group work activities, and the overall instructional design. Reducing TTT alone does not guarantee greater student participation; it must be accompanied by purposeful pedagogical interventions that alert students’ awareness and create willingness to communicate (WTC). As such, this study offers pedagogical implications and strategies that educators can implement to maximize STT and reduce TTT.Master of Arts (M.A.
Investigating the Role of the Nrf2a Pathway on the Extension of the Exocrine Pancreatic Tail, Exocrine Pancreas Function, and the Glutathione Response in Perfluorobutanesulfonic Acid Developmentally Exposed Zebrafish (Danio rerio)
No full textPer-and poly-fluoroalkyl substances (PFAS) are ubiquitous, persistent environmental contaminants associated with adverse health effects involving oxidative stress. While some longer-chain PFAS chemicals have been phased out, the environmental concentrations of shorter-chain versions like perfluorobutanesulfonic acid (PFBS) are increasing. Previous studies show that zebrafish embryos exposed to PFBS have developmental deformities including increased incidence of stunted pancreata. However, the functional impact and mechanisms behind this phenotype are poorly understood. The transcription factor Nrf2a regulates the adaptive transcriptional response to oxidative stress, including several enzymes involved in the synthesis and utilization of the endogenous antioxidant glutathione. This work aims to investigate the impacts of developmental PFBS exposure on the pancreas, oxidative stress, and the role of Nrf2a. Homozygous wildtype or mutant zebrafish embryos with a mutation in the DNA binding domain were exposed to PFBS for 3-96 hours post fertilization (hpf), imaged at 96 hpf or grown to 9 days post fertilization (dpf) in water without PFBS, and imaged. At 9 dpf, mutant larvae had shorter exocrine pancreases compared to wild-type larvae with the same PFBS treatment, indicating this phenotype likely involves redox stress. To assess exocrine pancreas function, lipase and protease activity were measured. At 9 dpf, both lipase and protease activity weren’t significantly different between wild-type and mutant larvae, regardless of PFBS exposure. To assess the effect of PFBS exposure on glutathione utilization, fish were exposed to PFBS for 3-96 hpf, rinsed, incubated in 200 μM monochlorobimane (MCB) for 1 hour, and imaged. Fluorescence was measured for six regions, with a significant difference in glutathione utilization in the eye lens, but not the pancreas. Thus, while Nrf2a plays a protective role in exocrine pancreas development during PFBS exposures, it may be due to other antioxidant systems. This study offers insights into the potential role of Nrf2a in exocrine pancreas extension, exocrine pancreas function, and glutathione utilization with developmental PFBS exposure in zebrafish.This work was supported by R21ES033532 to ART-L.Master of Science (M.S.)2026-02-0
Evaluate the stability of synthesized allicin and its reactivity with endogenous compounds in garlic
No full textThe study aimed to prepare allicin in large quantities and evaluate the effects of different conditions and endogenous substances (polyphenols and free amino acids) in garlic on its stability. The optimized synthesis conditions of allicin (DADS:HAc = 2:9, H2O2:DADS = 2:1.6, reacted for 6.5 h) were established based on response surface design. Allicin with 92.57% purity was obtained by high-speed counter-current chromatography. The results of allicin degradation experiment indicated that the degradation rate of allicin accelerated with the increases of initial concentration and temperature, the degradation process of allicin was good fit with two first-order kinetics (R2 > 0.97). The stability of allicin was higher in pH 2–5.8 than in pH 8–9. Apigenin, myricetin, and quercetin combined with peroxidase enhanced the stability of allicin. Cysteine, arginine, and histidine could react with allicin. These findings provide insights for optimizing for allicin storage and food processing applications
Evaluate the stability of synthesized allicin and its reactivity with endogenous compounds in garlic
No full textThe study aimed to prepare allicin in large quantities and evaluate the effects of different conditions and endogenous substances (polyphenols and free amino acids) in garlic on its stability. The optimized synthesis conditions of allicin (DADS:HAc = 2:9, H2O2:DADS = 2:1.6, reacted for 6.5 h) were established based on response surface design. Allicin with 92.57% purity was obtained by high-speed counter-current chromatography. The results of allicin degradation experiment indicated that the degradation rate of allicin accelerated with the increases of initial concentration and temperature, the degradation process of allicin was good fit with two first-order kinetics (R2 > 0.97). The stability of allicin was higher in pH 2–5.8 than in pH 8–9. Apigenin, myricetin, and quercetin combined with peroxidase enhanced the stability of allicin. Cysteine, arginine, and histidine could react with allicin. These findings provide insights for optimizing for allicin storage and food processing applications
Cost analysis of MOUD implementation and sustainability in Massachusetts jails
No full textIn 2018 Massachusetts mandated that county jails offer all FDA-approved medications for opioid use disorder (MOUD) to incarcerated individuals with OUD. Estimating costs needed to implement and sustain an MOUD program are not clearly known in jail facilities. The objective of this study was to identify the type of MOUD model deployed by the jails serving as research sites for the Massachusetts JCOIN hub, determine which resources were utilized at each stage of development, and estimate the associated costs
Characterizing Ubiquitin Conjugates and Deubiquitinase Activities on the Proteasome
No full textThe proteasome is a large protein complex responsible for degrading misfolded or damaged proteins tagged with ubiquitin modifications, thereby maintaining proteostasis in all eukaryotic cells. Before these proteins enter the proteasome for proteolysis, ubiquitin modifications are removed by a group of enzymes known as deubiquitinases (DUBs). DUBs can either cleave ubiquitin directly from substrate proteins or disassemble ubiquitin chains. They exhibit distinct activities and preferences for a wide variety of complex ubiquitin chains with different linkages and architectures. Understanding how proteasome-associated DUBs achieve selectivity for specific substrates is essential for elucidating the regulation of the ubiquitin system. This dissertation presents our efforts to investigate the profile of ubiquitin conjugates on the proteasome, as well as the impact of the proteasome-associated DUBs, UCH37 and USP14, on proteasome composition and stoichiometry. Our lab previously reported that UCH37 can enhance its debranching activity towards K48-linked branched ubiquitin chains when it is in the context of the proteasome. Previous studies on USP14 showed its en bloc cleavage on ubiquitin chains when proteasome is present. Despite the established roles of these two DUBs, the specificities and contributions to proteasome function remain poorly understood. Therefore, this thesis addresses how the depletion of UCH37 and USP14 affect proteasome composition and stoichiometry, as well as proteasome substrates. In our current study, we utilized CRISPR editing to generate various proteasome cell lines, purified proteasomes to characterize their activity and assembly, and then assessed ubiquitin profiles and substrates using mass spectrometry. Our results suggest that our purification method is efficient and effective to obtain fully assembled 26S proteasome. Additionally, the ubiquitin western blots imply reduced proteasome ability to process ubiquitinated conjugates. Furthermore, using DUB-based analysis and middle-down mass spectrometry, we studied ubiquitin linkage types and abundance on the proteasome. Our results indicate that proteasome substrates are mostly mono-ubiquitinated or modified with short K48-ubiquitin chains. Lastly, we identified a set of proteasome substrates and interactors are correlated with the depletion of DUBs, as well as changes in the protein abundance of proteasome subunits, using quantitative proteomics. Our results imply that DUBs act on their ubiquitinated substrates to regulate the degradation function of the proteasome. Overall, these findings advance the understanding of DUBs and proteasome substrates and will aid in developing biochemical strategies to explore their roles in various cellular processes.Doctor of Philosophy (Ph.D.
Training Tree Workers to Prune: How education impacts the health of the urban canopy in Massachusetts
No full textAs urban populations expand and climate change increases incidents of extreme weather, cities need sustainable ways to mitigate and adapt to these effects while supporting the health of their populations. Urban trees are a critical component of climate resilience and public health, but tree maintenance can be expensive and often beyond strained municipal budgets. Pruning trees in urban landscapes, especially early in a tree’s life, can result in savings over the long term. To prune a young tree effectively, minimizing injury to the tree and maximizing structural and environmental benefits, requires a combination of knowledge and skills. Municipalities have different ways of meeting this demand for skilled labor, and these decisions affect the outcomes for the health and longevity of the urban forest. To define the population of municipal workers who are pruning trees and determine the qualities and quantity of the tree pruning training they receive, I surveyed tree wardens throughout Massachusetts for information about pruning cycles, the workers pruning trees, and training the workers receive. Using research-based best practices, I developed a rubric that can be used to analyze training for essential instructional elements. The survey established that both Massachusetts tree wardens and pruning workers have a range of backgrounds. A large proportion of pruning workers are not arboricultural professionals, and this underscores the importance of effective training. Most training occurs on-the-job, led by a certified arborist. The fusion of the existing content-area expertise of the trainer with instructional techniques will result in more effective training with better outcomes for municipal trees. Successful training elements can be generalized and applied in other locations, resulting in a healthier, more mature urban canopy, a concomitant increase in environmental benefits, and cost savings that can be reinvested in urban forest management.Massachusetts Department of Conservation and RecreationMaster of Science (M.S.