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Transient Grating Spectroscopy: Compact System Geometry Developments and Improved Software
No full textTransient grating spectroscopy (TGS) is a rapid, non-destructive technique for measuring the thermal, elastic, and acoustic properties of the top several microns of a reflective surface. It has uses across many areas of materials research. Current TGS systems require complex optics tables taking up cumbersome amounts of space, restricting TGS to a predominantly lab-based method. This thesis first outlines a new design for TGS systems: an asymmetric probe, planar (APP) geometry, which enables TGS to be shrunk and simplified, lowering the barrier to entry and allowing for wider adoption in labs and industry. This Mini-TGS system was benchmarked against an existing system on a single-crystal tungsten sample, showing it produces the same SAW frequency as the benchmark system. The design enables TGS to be more widely adopted for use in more varied and compact environments because of its smaller size and simplicity. This thesis then outlines a study of reactor pressure vessel (RPV) coupons aimed at further understanding how properties evolve as a function of time in a reactor, as a step towards demonstrating that TGS can reliably detect if an RPV is fit for service. Ultimately, this work unveiled problems in the TGS fitting code. Lastly, this thesis details the software changes to the general TGS fitting code made to improve the fitting code in response to the RPV study.S.B
Composition-Dependent Structural, Phonon, and Thermodynamical Characteristics of Zinc-Blende BeZnO
No full textBoth ZnO and BeO semiconductors crystallize in the hexagonal wurtzite (wz), cubic rock salt (rs), and zinc-blende (zb) phases, depending upon their growth conditions. Low-dimensional heterostructures ZnO/BexZn1-xO and BexZn1-xO ternary alloy-based devices have recently gained substantial interest to design/improve the operations of highly efficient and flexible nano- and micro-electronics. Attempts are being made to engineer different electronic devices to cover light emission over a wide range of wavelengths to meet the growing industrial needs in photonics, energy harvesting, and biomedical applications. For zb materials, both experimental and theoretical studies of lattice dynamics ωj(q→)
have played crucial roles for understanding their optical and electronic properties. Except for zb ZnO, inelastic neutron scattering measurement of ωj(q→)
for BeO is still lacking. For the BexZn1-xO ternary alloys, no experimental and/or theoretical studies exist for comprehending their structural, vibrational, and thermodynamical traits (e.g., Debye temperature ΘD(T);
specific heat Cv(T))
. By adopting a realistic rigid-ion model, we have meticulously simulated the results of lattice dynamics, and thermodynamic properties for both the binary zb ZnO, BeO and ternary BexZn1-xO alloys. The theoretical results are compared/contrasted against the limited experimental data and/or ab initio calculations. We strongly feel that the phonon/thermodynamic features reported here will encourage spectroscopists to perform similar measurements and check our theoretical conjectures
Electrochemical Strategy for Low-Cost Viral Detection
No full textSexually transmitted infections, including the human immunodeficiency virus (HIV) and the human papillomavirus (HPV), disproportionally impact those in low-resource settings. Early diagnosis is essential for managing HIV. Similarly, HPV causes nearly all cases of cervical cancer, the majority (90%) of which occur in low-resource settings. Importantly, infection with HPV is six times more likely to progress to cervical cancer in women who are HIV-positive. An inexpensive, adaptable point-of-care test for viral infections would make screening for these viruses more accessible to a broader set of the population. Here, we report a novel, cost-effective electrochemical platform using gold leaf electrodes to detect clinically relevant viral loads. We have combined this platform with loop-mediated isothermal amplification and a CRISPR-based recognition assay to detect HPV. Lower limits of detection were demonstrated down to 104 total copies of input nucleic acids, which is a clinically relevant viral load for HPV DNA. Further, proof-of-concept experiments with cervical swab samples, extracted using standard extraction protocols, demonstrated that the strategy is extendable to complex human samples. This adaptable technology could be applied to detect any viral infection rapidly and cost-effectively
Air quality co-benefits of carbon pricing in China
No full textClimate policies targeting energy-related CO2 emissions, which act on a global scale over long time horizons, can result in localized, near-term reductions in both air pollution and adverse human health impacts. Focusing on China, the largest energy-using and CO2-emitting nation, we develop a cross-scale modelling approach to quantify these air quality co-benefits, and compare them to the economic costs of climate policy. We simulate the effects of an illustrative climate policy, a price on CO2 emissions. In a policy scenario consistent with China's recent pledge to reach a peak in CO2 emissions by 2030, we project that national health co-benefits from improved air quality would partially or fully offset policy costs depending on chosen health valuation. Net health co-benefits are found to rise with increasing policy stringency
User-centered evaluation of visual generative AI for city design: an exploratory technology acceptance model analysis
No full textThis study explores the potential of visual generative artificial intelligence (visual GenAI) in augmenting city design workflows. Using customized DALL-E 3 interfaces, we facilitated engagement sessions with members of an academic planning community to assess their perceptions of AI-generated imagery before and after its use, with a focus on main street revitalization (n = 24 qualitative, n = 17 quantitative). Drawing on the Technology Acceptance Model, we assessed cognitive, operational, and participatory dimensions influencing user attitudes toward AI-assisted urban design. Perceived usefulness in cognitive and participatory tasks emerged as the strongest predictors of attitudes toward visual GenAI use, explaining up to 71% and 44% of the variance, respectively. While participants valued the ability to generate visuals and stimulate dialogue rapidly, challenges with prompt precision, output predictability, and interface usability limited broader accessibility. User expertise moderated perceptions, with higher proficiency participants generally expressing more positive attitudes toward its use. Our preliminary findings suggest that while visual GenAI may offer new opportunities to augment cognitive and co-design processes, its integration into city design workflows may also depend on diverse training datasets to address biases; human-centered design with clearer affordances and support for non-expert users; and, validation processes that maintain human oversight. This study contributes to the emerging research on human-AI work integration by providing initial empirical evidence on the opportunities and constraints of visual GenAI tools in city design contexts, while establishing a foundation for future research.Fulbright Canad
Characterizing population-level variation in mRNA splicing and implications for human genetic interpretation
No full textAlternative splicing is when a single gene sequence gives rise to multiple RNA sequences. DNA mutations in this gene sequence can alter this process, shifting the relative usage of RNA sequences. This relative usage is called percent spliced in (PSI). Sometimes changes in PSI triggers a change in function, happening at the level of a cell, organism, or of fitness. The consequences of splicing variability, and the contribution of genetic variation to this process, remains incompletely characterized.
In this thesis, we seek to characterize the splicing events specifically present in a subset of the human population. We use the Genotype-Tissue Expression project (GTEx), which encompasses genomic DNA sequence information and bulk mRNA data from 49 tissues in 838 individuals. In this dataset we implement a 3-component beta-binomal model using RNA-sequencing reads, at a tissue-specifc level, to reliably call splicing events present in a subset of the samples within a tissue. We call these naturally variable exons (NVEs), and identify a total 57,271 unique NVEs in GTEx. We find NVEs in a large portion of the transcriptome, existing in 75% of all protein-coding genes.
The beta-binomal model generates a population distribution of each NVE and we leverage that to estimate an NVE frequency at a PSI level of interest. This enables us to compare NVEs by their frequencies. We find that NVEs either tend to be rare in frequency ( ≤ 10%) in the population) or quite high in frequency ( ≥ 90%). We find that NVEs tend to be in 5' untranslated regions at higher frequencies, and tend to be in coding regions at lower frequencies.
60% of NVEs have been previously found to be modulated by genetic variants. We find that proximity to a splice site is one of the most important predictors in predicting if a genetic variant will impact splicing in GTEx, which enables better predictions over existing methods (increase in AUC by 0.39). Surprisingly, we find that NVEs tend to be in genetically constrained genes (depleted of loss-of-function mutations), with the lowest frequency NVEs occurring in the most constrained genes. We find a subset of genetically-modified NVEs that target genes in a manner consistent with inducing nonsense-mediated decay (NMD). We highlight a couple of such variants linked to diseases, such as those associated with heart disease.
These findings demonstrate that quantifying the population frequency of splicing events can reveal novel axes of molecular variability, and provide potential insight into the evolution of alternative splicing.Ph.D
Food Grade Synthesis of Hetero-Coupled Biflavones and 3D-Quantitative Structure–Activity Relationship (QSAR) Modeling of Antioxidant Activity
No full textBiflavonoids are a unique subclass of dietary polyphenolic compounds known for their diverse bioactivities. Despite these benefits, these biflavonoids remain largely underexplored due to their limited natural availability and harsh conditions required for their synthesis, which restricts broader research and application in functional foods and nutraceuticals. To address this gap, we synthesized a library of rare biflavonoids using a radical–nucleophile coupling reaction previously reported by our group. The food grade coupling reaction under weakly alkaline water at room temperature led to isolation of 28 heterocoupled biflavones from 11 monomers, namely 3′,4′-dihydroxyflavone, 5,3′,4′-trihydroxyflavone, 6,3′,4′-trihydroxyflavone, 7,3′,4′-trihydroxyflavone, diosmetin, chrysin, acacetin, genistein, biochanin A, and wogonin. The structures of the dimers are characterized by nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectroscopy (HRMS). In addition, we evaluated the antioxidant potential of these biflavones using a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay and the DPPH value ranges between 0.75 to 1.82 mM of Trolox/mM of sample across the 28 synthesized dimers. Additionally, a three-dimensional quantitative structure–activity relationship (3D-QSAR) analysis was conducted to identify structural features associated with enhanced antioxidant activity. The partial least squares (PLS) regression QSAR model showed acceptable r2 = 0.936 and q2 = 0.869. Additionally, the average local ionization energy (ALIE), electrostatic potential (ESP), Fukui index (F-), and electron density (ED) were determined to identify the key structural moiety that was capable of donating electrons to neutralize reactive oxygen species
Dynamical Characteristics of Isolated Donors, Acceptors, and Complex Defect Centers in Novel ZnO
No full textNovel wide-bandgap ZnO, BeO, and ZnBeO materials have recently gained considerable interest due to their stellar optoelectronic properties. These semiconductors are being used in developing high-resolution, flexible, transparent nanoelectronics/photonics and achieving high-power radio frequency modules for sensors/biosensors, photodetectors/solar cells, and resistive random-access memory applications. Despite earlier evidence of attaining p-type wz ZnO with N doping, the problem persists in achieving reproducible p-type conductivity. This issue is linked to charging compensation by intrinsic donors and/or background impurities. In ZnO: Al (Li), the vibrational features by infrared and Raman spectroscopy have been ascribed to the presence of isolated AlZn(LiZn)
defects, nearest-neighbor (NN) [AlZn−NO
] pairs, and second NN [AlZn−O−LiZn;VZn−O−LiZn]
complexes. However, no firm identification has been established. By integrating accurate perturbation models in a realistic Green’s function method, we have meticulously simulated the impurity vibrational modes of AlZn
(LiZn)
and their bonding to form complexes with dopants as well as intrinsic defects. We strongly feel that these phonon features in doped ZnO will encourage spectroscopists to perform similar measurements to check our theoretical conjectures
Report to the President for year ended June 30, 2025, MIT Corporate Relations
No full textThis report contains the following sections: About MIT Corporate Relations, Industrial Liaison Program, MIT Startup Exchange (STEX), In-Person Events and ILP Webinars, Goals for FY2026 and Beyond, and Impact
Reducing the Compositional and Structural Degeneracy of Planetary Interiors
No full textThe interior conditions of planets are highly uncertain, because two types of intrinsic degeneracies – compositional degeneracy and structural degeneracy – prevent precise characterization. In this thesis, I develop a planetary interior code package, CORGI, incorporating state-of-the-art physical properties of planet-forming materials. Using CORGI, I eliminate unmixed interior scenarios for Uranus, rule out the fossil-compressed formation hypothesis for high-density exoplanets, and establish a link between formation history and atmospheric composition for hypothetical Earth-like white dwarf (WD) exoplanets, reducing interior degeneracy for these planets. However, I also identify a novel carbon-rich interior composition for sub-Neptunes, introducing an additional degeneracy to this already ambiguous category.
It is heatedly debated that whether Uranus is a distinct-layer “ice giant” with greater than 70 wt% ice or a “rock giant” with compositional gradients and roughly equal amounts of ice and rock. Gravity field measurements from spacecraft, which directly probe interior mass distribution, are expected to resolve this debate. However, I show that the degeneracy will persist even with future Uranus Orbiter and Probe (UOP) mission, but the level of degeneracy can be reduced. My models indicate that only highly mixed interiors – either those with smooth density gradients or those with substantial light elements in the mantle and heavy elements in the atmosphere – are consistent with previous Voyager 2 measurements. Additionally, I demonstrate that the UOP can distinguish between high- and low-atmospheric metallicity scenarios and constrain the J6 harmonic, and potentially J8, if placed in close-in polar orbits, informing the mission and orbit design of UOP.
For exoplanets with no solar system counterparts, interior models are essential for understanding their composition, structure, formation, and evolution. I apply CORGI to a category of high-density planets that are consistent with greater than 50% core mass fraction, substantially higher than that of the Earth (33%). By combining planetary interior modeling with photoevaporation modeling, I investigate into one of the hypotheses – the fossil-compressed hypothesis – for the origin of high-density planets. My models revealed that most high-density planets are highly improbable to be fossil-compressed cores, because most or even all of the iron-silicate core is molten during the evolution, while the fossil-compressed hypothesis requires a solid core. Kolmogorov–Smirnov test statistics show that this result is robust for planets with both hydrogen-dominated and steam envelopes.
Planetary interior models sometimes reveal new degeneracies rather than resolving them. By combining interior, atmospheric chemistry, and transmission spectra models, I identify a new possible interior composition for sub-Neptunes: carbon-rich composition. I posit that sub-Neptunes formed between the “soot line” – a condensation line for refractory organic carbon – and the water snow line would have high bulk C/O ratios and a substantial carbon layer. Interior models revealed that such carbon-rich compositions are consistent with the masses and radii of sub-Neptunes, given appropriate atmospheric metallicity. Atmospheric chemistry and transmission spectra models found that the spectral features predicted for carbon-rich sub-Neptunes are compatible with observations by the Hubble Space Telescope and the James Webb Space Telescope.
Finally, I explore the connection between post-main-sequence evolutions and the atmosphere and interior conditions of hypothetical Earth-like planets orbiting WDs. I showed that first-generation WD planets that have experienced significant atmospheric loss and second-generation WD planets that are formed in WD debris disks under a more clement radiation environment can be distinguished by the presence of a hydrogen-dominated atmosphere. Additionally, the interior conditions of second-generation WD planets can be inferred from WD pollution observations.Ph.D