50107 research outputs found
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Stream Functioning Across an Endorheic Basin in the Dry Andes
No full textWater scarcity is a defining constraint for both ecosystem function and lithium resources development in the arid, high elevation region of the Puna Plateau in South America. Despite this, the processes that govern streamflow generation in the region remain poorly understood. This study aims to characterize streamflow dynamics in the Salar de Pastos Grandes watershed using an integrated approach drawing from physical, geochemical and remotely sensed hydrologic data. Weekly streamflow gauging served as the primary dataset which was supported by insights from environmental tracers, climate data and remotely sensed vegetation indices. Streamflow fluxes are modulated by topography, discrete precipitation events, temperature fluctuations and vegetation extents. Perennial streamflow is generated in catchments with significant area above 5000 meters above sea level. In contrast, ephemeral flows are responsive to precipitation and groundwater releases from bofedal wetlands. All basin waters were recharged >65 years ago and there is a gap in streamflow flux and modern precipitation inputs, indicating there is likely an additional source of relic water to streams. These findings inform a conceptual model for stream functioning in the dry Andes and these results have implications for freshwater availability studies and process-based groundwater models in this region.Master of Science (M.S.)2026-09-0
SCOPOLETIN REDUCES FAT ACCUMULATION IN CAENORHABDITIS ELEGANS
No full textScopoletin, a naturally occurring coumarin, has been associated with the regulation of lipid metabolism. In this study, we used Caenorhabditis elegans, a well established in vivo nematode model, to explore the role of scopoletin in fat accumulation. C. elegans treated with scopoletin (200 µM) exhibited significantly reduced triglyceride levels compared to the control, without significantly affecting food intake or locomotive activity in wild type C. elegans. The reduction in fat accumulation by scopoletin suggests that scopoletin may regulate lipid metabolism independently of food intake and energy expenditure. Further investigation of the underlying molecular mechanisms is required to determine whether scopoletin modulates lipid metabolism through specific genetic pathways.Master of Science (M.S.)2026-09-0
An Open Access Policy Review and Considerations on Future Relevance
No full textPresentation at the 2025 Charleston Conference (virtual) about the UMass Amherst Open Access Policy review with discussion of the relevance of open access policies more generally in the current scholarly publishing landscape
Growing Up in the Digital Age: Perceptions of Parenting and Experiences of Online Opportunities and Risks among Urban Chinese Adolescents
No full textThis dissertation investigates the Internet use of urban Chinese adolescents, focusing on their encounters with online opportunities and risks, their negotiation of parental mediation, and the influence of socio-cultural contexts, including the Chinese concept of Guan (caring governance). Adopting a mixed-methods approach, the research integrates survey data and in-depth interviews across three empirical studies to provide a child-centered and culturally nuanced understanding of urban Chinese adolescents' digital experiences.
The Internet presents a dual reality for young people: it offers significant online opportunities for learning, social connection, self-expression, and identity construction, yet simultaneously exposes them to notable online risks, such as harmful content, cyberbullying, and privacy violations. Parents employ various parental mediation strategies (e.g., restrictive rules, active discussion, co-use) to manage these experiences, practices which are deeply intertwined with broader parenting styles and cultural values. While previous research has explored these dynamics, a significant gap exists in understanding how these constructs manifest and interact within the unique socio-cultural landscape of urban China, particularly concerning indigenous parenting concepts like Guan and the balance between culturally ingrained parenting philosophies and evolving family dynamics in a rapidly changing media environment. China, with its vast population of young Internet users and specific governmental regulations shifting usage towards the home, offers a critical yet under-explored context for examining these interactions.
This dissertation makes substantial scholarly contributions by advancing child-centered perspectives on digital rights, emphasizing adolescent agency in navigating the digital world. It enriches the understanding of digital childhood and parenting by providing a culturally contextualized view of urban Chinese adolescents' Internet use, particularly through the exploration of Guan. The findings offer practical implications for parents, educators, and policymakers, advocating for a move beyond simplistic views of Internet use towards fostering critical thinking, self-regulation, and digital citizenship. It calls for culturally tailored, child-centered interventions that acknowledge adolescents' needs for autonomy and participation, and for incorporating their perspectives into policy and educational program development.Dissertation Completion Fellowship granted by the Graduate School at the University of Massachusetts Amherst;
Suopis Communication Graduate Fellowship granted by the Department of Communication at the University of Massachusetts Amherst;
Graduate School Fieldwork Grant by the University of Massachusetts Amherst;
Anca Romantan International Fieldwork Grant by the Department of Communication at the University of Massachusetts AmherstDoctor of Philosophy (Ph.D.)2026-09-0
Does Segment Reporting Influence Investors’ Judgments? The Debiasing Role of Roll-Back Reconciliation
No full textThis study examines whether segment reporting changes affect investors’ judgments. Without changes in actual performance at both the granular operating unit level and the overall firm level, I examine whether changes in segment composition influence investors’ perceptions of firm performance and whether this effect is mitigated by presenting both roll-back and roll-forward reconciliations. Specifically, I predict and find that, under the current regulation (i.e., where only a roll-forward reconciliation is required), favorable segment composition changes lead to greater investment willingness compared to neutral segment changes. In contrast, when both roll-back and roll-forward reconciliations are presented, the differences between favorable segment changes and neutral segment changes are eliminated. These findings provide regulators with an easy-to-implement reconciliation approach, which can help investors better understand segment composition changes.Doctor of Philosophy (Ph.D.)2026-09-0
Developing Multiplexed Fluorogenic RNA-based Sensors for Live-Cell and Subcellular Imaging
No full textMultiplexed detection of target analytes, such as small molecules and RNAs, within live systems is essential for studying correlations among diverse biological processes and disease mechanisms. However, the multiplexing capacities of most reported imaging tools are limited by spectral overlaps of fluorophores. Recently, fluorogenic RNA-based sensors have emerged as a powerful imaging tool in living cells. Compared to conventional fluorescence imaging methods, fluorogenic RNA-based sensors offer key benefits, including genetic encodability, high modularity, ease of programming, and ability to target a wide range of analytes. The feature of reversible binding between a fluorogenic RNA aptamer and its fluorophore offers a unique opportunity to develop a sequential imaging strategy to expand the multiplexing capacity of fluorogenic RNA-based sensors in living cells.
In this thesis, I will present our efforts in developing fluorogenic RNA-based robust multiplexed sensor systems for live-cell and subcellular imaging of various target analytes. First, we developed a highly versatile multiplexed imaging system using fluorogenic RNA-based sensors, named “sequential Fluorogenic RNA Imaging-Enabled Sensor” (seqFRIES). Since fluorogenic RNA binds to its fluorophore in a reversible manner and the fluorophores are membrane permeable, seqFRIES employs multiple imaging and washing cycles to overcome the spectral overlap issues of these fluorophores. We identified four orthogonal fluorogenic RNA aptamer/dye pairs, including Broccoli/3,5-difluoro-4-hydroxybenzylidene-1-trifluoroethyl-imidazolinone (DFHBI-1T), dinitroaniline (DN)-binding aptamer (DNB)/tetramethylrhodamine-dinitroaniline (TMR-DN), Corn/3,5-difluoro-4-hydroxybenzylidene imidazolinone-2-oxime (DFHO), and Pepper/4-[(Z)-1-cyano-2-[5-[2-hydroxyethyl(methyl)amino]thieno[3,2-b]thiophen-2-yl]ethenyl]benzonitrile (HBC620), which can be successfully imaged sequentially within the same living cells. We were also able to use the seqFRIES system to monitor two signaling molecules, cyclic diguanylate (c-di-GMP) and guanosine tetraphosphate (ppGpp), under antibiotic treatment in bacterial cells. By further engineering fluorogenic RNA-based sensors for messenger RNA (mRNA) targets, we showed seqFRIES can be used to track cellular level changes of four endogenous mRNAs, ATCB, HER2, STAT3, and TK1, in response to treatment with a potential anticancer drug, Trichostatin A. This innovative RNA-based multiplexed imaging platform holds great potential for investigating complex cellular pathways involving multiple biomolecular components.
In a follow-up project, to further enhance the reproducibility, efficiency and operational ease of using of seqFRIES, we developed an automated seqFRIES system (auto-seqFRIES) by incorporating a microfluidic device for sequential imaging. Auto-seqFRIES uses a precisely controlled pressure pump for rapid dye addition and washing through dynamic fluid flow. The microfluidics system can be secured under a microscope and be programmed to capture fluorescence images at precise times and locations, enabling accurate and consistent monitoring of cellular fluorescence signals. We showed that auto-seqFRIES can be reliably performed for rounds of fluorogenic RNA imaging with no detectable reduction in fluorescence signals. Compared to the previous manual methods, this lab-on-a-chip approach greatly reduced processing time and improved imaging precision.
In the seqFRIES project, we demonstrate that fluorogenic RNAs can be recruited to distinct subcellular locations, such as nucleoli and condensates. As an extension of this effort, we aim to develop an imaging approach that can localize fluorogenic RNA-based sensors specifically into mitochondria to study mitochondrial metabolism. As a preliminary attempt, we screened five reported mitochondrial import RNA sequences and identified the sequence with the highest import efficiency. In future efforts, we aim to further improve mitochondrial targeting ability by designing tandem repeats of the RNA sequences, and using directed evolution to identify variants with enhanced mitochondrial import abilities. These identified mitochondrial import sequences will be further used to tag fluorogenic RNA-based sensors for imaging molecules crucial to mitochondrial metabolism such as S-Adenosyl methionine (SAM), S-Adenosyl-L-homocysteine (SAH), and adenosine diphosphate (ADP). We envision that the mitochondrial imaging tool in live cells will uncover novel insights in mitochondrial biology.NIH Traineeship [T32GM139789], Chan Zuckerberg Initiative Dynamic Imaging program [2023-321170], NSF CAREER award [1846152], Alfred P. Sloan Research Fellowship, Camille Dreyfus Teacher-Scholar Award, UMass Amherst start-up grantDoctor of Philosophy (Ph.D.)2026-09-0
Exploring the Endorsement of Gender Stereotypes and Physical Activity in Young Women
No full textBackground: Physical behaviors (PBs), defined as physical activity (PA) and sedentary behavior (SB), are consistently less favorable in women than men. Extensive qualitative research has identified gender norms as a well-known barrier to women’s PA, but they have yet to be clearly conceptualized and quantified. The purpose of this study was to (1) investigate the relationship between benevolent sexism endorsement (BSE) and PB, (2) explore women’s experiences with sexism in PA settings, and (3) identify sexism constructs within focus group discussions.
Methods: Participants completed the Ambivalent Sexism Inventory (0–5 scale) and wore a hip-worn activity monitor for 7 days. Spearman correlations were calculated between BSE and PB. A 90-minute focus group (n = 4) was transcribed and coded to identify themes and sexism constructs.
Results: Participants (n = 20, 20.7 ± 1.3 years) exceeded PA guidelines and reported low BSE scores (1.8 ± 0.76). Weak associations were found between BSE and objectively measured PA (r = −0.19 to r = −0.37) and ST (r = 0.14). Focus group results yielded four themes: (1) Age-Related Decline in PA, (2) Parental Roles, (3) Peer Relationships/Friendships, and (4) Physical Education Teachers/Coaches.
Conclusion: As hypothesized, associations between BSE and PA outcomes and SB were negative and positive, respectively. Focus group themes were related to benevolent sexism constructs. Future research should be conducted in larger, more diverse samples and consider other factors that may impact one’s endorsement of benevolent sexism.UMass SOAR Fun
Advancing Aquatic Biodiversity and Relative Abundance Monitoring: Employing Environmental DNA (eDNA) to Assess Diadromous Fish Populations and Ecosystem Health
No full textEnvironmental DNA (eDNA) analyses allow for the detection of species by isolating and analyzing genetic material shed into the environment. Despite their growing use, eDNA methods remain constrained by uncertain detection probabilities, limited calibration with traditional monitoring, signal variability, and inconsistent methods. This dissertation explores the functional application of eDNA for ecological monitoring and fisheries management across three complementary studies. In Chapter Two, I used eDNA metabarcoding to assess aquatic vertebrate and diadromous fish biodiversity after the Elm Street Dam removal in the Jones River watershed. From 2020 to 2021, species richness declined at downstream sites, while upstream sites gained richness but lost functional diversity. Multivariate statistical analyses revealed significant temporal and spatial differences in community composition, consistent with early-stage ecological restructuring. In Chapter Three, I developed mechanistic and statistical models to estimate river herring abundance across three connected ponds using log-transformed eDNA concentrations from ten synchronized sampling events. A single electronic resistivity fish counter in the most downstream pond served as an anchor for calibration. eDNA concentrations tracked two-day and cumulative fish counts well (site-level R² = 0.94). Predictive accuracy declined in a watershed-scale linear model (R² = 0.58), but improved when a linear mixed model was used that accounted for basin volume and distance from the e-count station (R² = 0.76). I then developed a mechanistic model incorporating site-specific scaling based on hydrological distance, basin surface area, and DNA decay. The best-performing models, using uniform sensitivity-scaled exponents (α = 0.01) at site (R² = 0.98) and watershed (R² = 0.97) scales demonstrated eDNA’s potential to estimate fish abundance at sites unsampled by traditional methods using a single traditional anchor count. In Chapter Four, I compared eDNA quantitative polymerase chain reaction (qPCR) estimates with four traditional fish relative abundance monitoring methods across seven case studies. eDNA aligned closely with resistivity counters, electrofishing, and video surveys, but not fyke nets. A multispecies occupancy model highlighted higher detection certainty for eDNA approaches and exposed traditional method-specific detection biases. Together, these studies demonstrate eDNA’s utility for scalable, quantitative ecological monitoring, advancing data-driven frameworks for biodiversity assessment and resource management in aquatic ecosystems.Doctor of Philosophy (Ph.D.
Lipid Structures and Membrane Energetics Controlling Inner Membrane Domain Organization in Mycobacteria
No full textMycobacterium species pose a significant global health threat due to emergence of drug-resistant strains and persistent infections. These pathogens possess a complex cell envelope making them impermeable to many antibiotics. Our current understanding of the mycobacterial cell envelope is limited, obstructing the efforts to exploit it as a therapeutic target. This study investigates the plasma membrane, the innermost layer of the mycobacterial cell envelope. Mycobacterial plasma membrane laterally partitions during active growth forming distinct domains called the inner membrane domain (IMD). During stress, the IMD de-partitions coinciding with impaired growth.
Through this study, we identify a unique lipid structure- tuberculostearic acid to be important in reorganizing the IMD under membrane stress. Through a genetic screen, we identify the gene, cfa to be involved in the biosynthesis of tuberculostearic acid. We further validated its enzymatic activity as a methyltransferase.
In the second part of the thesis, we explore the biochemical basis behind IMD partitioning. Using genetic knockdowns of proteins in the electron transport chain (ETC) and respiratory chain chemical inhibitors, we demonstrate that membrane energetics, particularly the formation of a proton gradient to be crucial for stress induced de-partitioning of the IMD.Doctor of Philosophy (Ph.D.