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Intrasample Os-isotope disequilibrium in young volcanic rocks
No full textThis dissertation introduces a novel progressive digestion technique for osmium (Os) isotope analysis, capable of sequentially isolating Os from surface contaminants, bulk silicate matrix, and refractory phases within a single whole-rock powder. This approach overcomes challenges in distinguishing pristine mantle signatures from contamination in young volcanic rocks. Applied to basaltic reference materials BHVO-2 and EN026 10D-3, the method revealed intrasample Os-isotope heterogeneity and labile, radiogenic contamination in BHVO-2, likely introduced during sample preparation. For EN026 10D-3, while Step II Os-isotope ratios align with primitive upper mantle, radiogenic labile Os underscores the vulnerability of low-Os MORBs to disturbance—emphasizing the need for high-fidelity analytical protocol. This progressive digestion technique for Os isotope analysis was applied to studies of lavas from Hawaii and Laacher See (Germany) tephra
Mauna Loa lavas (1852–2022), exhibit a nearly constant Os-isotope range (187Os/188Os = 0.134–0.136) across ~200 years, despite subtle surficial contamination capable of shifting ratios by up to ~2%. Intrasample heterogeneity in older flows likely reflects magma mixing. The striking invariance of Os isotopes—unlike variable lithophile systems—suggests isotopic similarity to the “shared” mantle source with Kīlauea or, alternatively, low Os contribution due to residual sulfides. Mauna Loa’s more radiogenic 187Os/188Os ratios (average 0.1357 ± 0.0013) compared to that of Kīlauea (0.1285 ± 0.0005) supports a recycled component with high Re/Os in its source.
Os and Pb isotope data from the Laacher See tephra are used to track open-system magmatic processes. Os-isotopic heterogeneity in the Rothenberg basanite records variable contamination, while increasing Os and Pb ratios through differentiation reflect sulfide fractionation and subtle assimilation. A downward Os-isotope trend in evolved units suggests convective redistribution of sulfide phases. Isotopic overlap with Eifel lithospheric mantle xenoliths indicates a parental melt from enriched subcontinental lithosphere, modified by crustal interaction.
This work demonstrates the exceptional sensitivity of Os isotopes to magmatic sources and processes and establishes a robust framework for decoding mantle and crustal signatures in young volcanic systems especially those prone to disturbance due to their low Os content
Equilibration of Alluvial River Channel Geometry to Unsteady Boundary Conditions
Full text linkThe morphology of an alluvial river is the culmination of dynamic processes interacting across scales. When the boundary conditions of a fluvial system are modified, feedback effects among these processes reshape the channel by altering the flow of water and sediment. Environmental stressors, therefore, have the potential to propagate signals of change from watershed to grain scale features in a river channel. I trace the influence of modern climate change across these scales by first quantifying changes in the generation of surface runoff and sediment supply at watershed scales. I then identify how the subsequent changes in hydrological and sedimentological processes affect reach scale channel morphology. Finally, I connect the physical expression of these processes to grain scale changes in sediment transport dynamics, which provides a mechanism for channel restructuring. My analysis reveals that temperature-sensitivity at the watershed scale can be manifested in within-channel structures and hydraulic geometry. As the supply of water and sediment is modulated by external forcings, fluvial processes at the reach scale respond by altering the routing of material in time and constructing new features in space. The effect of sediment supply variation, in particular, is evident even at the scale of an individual particle being transported. The synthesis of my analysis demonstrates how the response of local processes to global boundary conditions results in the observed channel form in alluvial rivers
Phospho-regulation of cytokinetic proteins in fission yeast
No full textEvery dividing eukaryotic cell must coordinate cytokinesis with mitosis in both space and time to ensure that each daughter cell receives equal complements of the duplicated genetic material. This process is crucial for maintaining proper growth and development in many organisms. The importance of cytokinesis is further supported by the finding that its failure causes polyploidy, which, in turn, can result in defective mitoses and chromosomal instability. These defects have varying degrees of cellular consequences and have been linked to the development of various diseases like cancer. Nearly one billion years ago, the molecular mechanism underlying cytokinesis through a contractile actomyosin ring originated in a common ancestor of amoebas, fungi, and animals. These organisms share much of the same cytokinetic machinery, meaning that knowledge gained from studying the well characterized model organism Schizosaccharomyces pombe will provide important mechanistic insights behind human cellular controls. While many of the individual components of the CAR have been identified, we do not fully understand how they are regulated and time and space and how this contributes to the fidelity of cytokinesis. My thesis work focused on understanding how protein phosphorylation allows cytokinetic proteins to acquire temporal and spatial specificity. My work identified the highly conserved protein phosphatase PP2A-B56 promotes efficient cytokinesis through the anillin-like protein Mid1. We found that cells lacking Par1 had reduced levels of cellular Mid1, resulting in cytokinetic defects. We were able to rescue these cytokinetic defects by restoring the levels of Mid1 in par1 cells, thereby solidifying the connection between PP2A-B56, Mid1 abundance, and cytokinesis efficiency. Previous groups have shown that increased Mid1 levels also lead to cytokinetic defects. This requirement for regulating Mid1 expression could represent a conserved principle because altered levels of the Mid1-related protein anillin in higher eukaryotes results in similar cytokinetic failure. Next, I became interested in the conserved protein kinase Pdk1 and its potential role in regulating cytokinesis. Pdk1 is considered a ‘master’ kinase because of its ability to phosphorylate and activate more than 23 downstream protein kinases that are involved in signaling pathways ranging from actin organization, inflammation, cell adhesion and motility. Unsurprisingly, the dysregulation of Pdk1 has been associated with numerous cancers and is believed to lead to poor clinical outcomes. Previous studies performed in fission yeast suggest that cells lacking Pdk1 have numerous cytokinetic defects, including delayed contractile actomyosin ring assembly and diffuse Mid1 localization. My thesis work aimed to further characterize these defects and to understand if Pdk1 has an additional role in regulating cytokinesis. In the absence of Pdk1, we found that cells exhibit cytokinetic defects that likely arise from structural issues with the contractile actomyosin rings. We also have identified a potential role of Pdk1 in regulating the assembly of eisosomes through phosphorylation of Pil1. Collectively, this thesis considers how spatial and temporal control is generated within a defined biological system. These results have the potential to uncover principles that operate in higher eukaryotes across varying scales of time and space
Matty\u27s First Hike: Hiking Spain\u27s northwest coast with a baby and a beagle
Full text linkNew parents venture along the coast of Galicia, from the Cliffs of Loiba to O Esteiro and back, with their son in a carrier
News and Notes
Full text linkA Look Back at the Appalachian Mountain Club’s Long-Ago Membership Practices. 350th Year Since King Philip’s War on Talcott Mountain in Connecticut. Northeast Snow Survey Feasibility Study. All Out: AMC’s Action Plan for 2025-2030
Old, Flat, and Slow: Interior Greenland Snow and Ice Dynamics Revealed with GNSS
Full text linkThe interior dry snow zone region of the Greenland Ice Sheet can no longer be confidently considered a reliably melt-free region, yet our ability to investigate and quantify the dynamic nature of this landscape is hindered by its remoteness. To overcome this challenge, this work describes a novel, low-cost, low-power GNSS (positioning) instrument that enables simultaneous measurements of (1) ice accumulation/ablation changes and (2) 3D ice flow. Deployed in a dense array, these GNSS instruments achieve similar performance to scientific-grade, commercial options (cm- to mm- precision), yet operate at \u3c 60% of the power and \u3c 34% of the hardware cost. Over a three year campaign, we analyze spatial and temporal patterns of accumulation in this region, using a technique called GNSS interferometric reflectometry (GNSS-IR). Observations with this technique show low bias and high precision relative to a validation study (-2.1 ± 2.9 cm), while we also demonstrate for the first time how GNSS-IR can reveal cm- to m- scale surface roughness, a critical yet often neglected measurement due to longstanding observational challenges. Patterns of accumulation show a spatial dependence linked to surface slope (~+0.7 mm w.e. km^-1 westward away from the divide) while surface roughness has a temporal dependence likely driven by wintertime high winds. Next, we combine GNSS-IR surface heights with the geodetic position time series of the antenna to derive surface elevation changes, which are compared to coincident ICESat-2 laser altimetry elevations. Observations of the surface show a millimeter-level relative bias and cm-level precision (-0.9 ± 3.8 cm) compared with the satellite altimeter, demonstrating for the first time that this technique is a viable ground-truthing method, while ICESat-2 performance has continued to exceed mission performance requirements. Finally, we examine station positioning through time to show a sensitivity to dynamic ice thinning and firn densification, two parameters than cannot be finely observed with space-based methods in this region. Together, these results provide the first ground‑based, high‑resolution picture of interior ice‑sheet change—capturing accumulation, roughness, surface elevation, and strain in one unified dataset. Our approach dramatically lowers logistical barriers, opening the interior of Greenland (and other remote regions) to sustained, quantitative monitoring at unprecedented spatiotemporal resolution
How to Remember Names Lesson Plan
No full textThis is an introductory lesson intended for any high school- or college-aged student who wants to learn how to deepen connections with others, whether for personal or professional relationships. Through a combination of lecturettes, discussions, reflection time, and activities/ quizzes, students will learn and apply their knowledge about the benefits, science, history, and strategies of remembering people’s names so that they are able to use names in future conversations. The final activity will be a simulation of real life scenarios where students will have to either remember and use a stranger’s name or practice asking for their name, whether they forgot their name or are meeting them for the first time
Rainwater Harvesting Instrumentation Design
No full textMexico City faces a severe water crisis, with millions of residents lacking reliable access to clean water. Isla Urbana, a non-profit organization that develops rainwater harvesting (RWH) systems to address this issue, has installed over 43,000 systems to provide essential water for underserved communities. However, a key challenge remains: there is no reliable way to measure the amount of water harvested by these systems. The current water meters in use are expensive, technically complex, and often require Wi-Fi for operation, making them inaccessible in many locations. To address this, the team found a cost-effective, simple, and accessible water meter and designed a dual-sensor data collection process. This dual-sensor design combines a mechanical counter to track total water volume and a removable digital sensor to measure instantaneous flow rates. This design prioritizes affordability and is adaptable to different system configurations and locations, enabling Isla Urbana to gather reliable, verifiable data on water harvesting. The digital sensor provides real-time data on flow rates, allowing Isla Urbana to assess the impact of their RWH systems on local flooding during storms. The modular design helps reduce costs by allowing for the deployment of the digital sensor only where necessary. The system processes data locally using an Arduino and stores it on an SD card, which can be periodically collected without needing Wi-Fi. Additionally, the Python-based data aggregation platform analyzes and validates the data, providing Isla Urbana with actionable insights to improve water access, reduce flooding, and enhance overall impact
Electric Dyno Design
No full textDartmouth Formula Racing (DFR) is a student-run group that designs, builds, and competes with a custom, formula-style race car in two annual SAE events: the Formula Hybrid + Electric (FH+E) competition in New Hampshire and Formula SAE in Michigan. Although these competitions have distinct rules, many technical requirements overlap—particularly regarding battery performance and safety. This project addresses DFR’s need for a standard, robust method to assess the performance of its car’s battery pack under simulated racing conditions. We iterated upon a battery discharge apparatus (BDA) to create a validated testing protocol, a functional BDA and 50V battery segment with integrated cooling features to safely test and log critical metrics (e.g., cell health, temperature, voltage, current), and a dedicated testing segment enclosure. This validated testing protocol measures capacity, discharge cycles, and thermal performance under load, yielding insights into the team’s overall powertrain strategy. This new setup lets the team test multiple battery packs and battery segments, as well as the accumulator, without removing it from the car, saving time and improving resource efficiency. Designed with cost-effectiveness in mind, it leverages spare parts, readily available materials and user-friendly documentation to create a full solution to characterize the batteries they use. Built-in fault detection and established procedures enhance safety and reduce the risk of mishandling. The battery discharge apparatus, segment and testing protocol provide student engineers hands-on exposure to real-world battery management principles, creating a lasting educational benefit. Looking ahead, plans include refining the battery discharge apparatus PCB design, exploring alternative sensors for greater accuracy, and adapting the enclosure for Tesla‐sponsored battery modules, ensuring a durable, reusable platform for subsequent Dartmouth Formula Racing teams
From Test Coverage to Non-Corruption Exploits: Rethinking Fuzzing for Software Vulnerability Discovery
No full textFuzzing is one of the most effective techniques for improving software reliability and security. By automatically generating diverse inputs and executing programs at scale, it exposes numerous implementation flaws and design weaknesses. This dissertation enhances the effectiveness and efficiency of fuzzing through three complementary components.
First, applying fuzzing to software libraries requires high-quality harnesses that invoke APIs with valid sequences and parameters, yet manual harness development is labor-intensive and error-prone. This work proposes a framework that automatically generates fuzzing harnesses by extracting real-world API usage patterns from external source code. The underlying static analysis efficiently recovers API interactions at scale without sacrificing precision, enabling the synthesis of effective harnesses for previously untested library functions.
Second, traditional fuzzing relies on coverage-based guidance to explore a program’s input space. While effective for general code exploration, such metrics overlook deeper semantic behaviors. This dissertation introduces a fine-grained coverage guidance technique that captures program semantics beyond simple code coverage, facilitating the detection of complex logical and semantic issues that conventional fuzzers may miss.
Third, modern systems depend on standardized specifications for interoperability. However, real-world implementations often diverge from these standards, introducing subtle inconsistencies and security risks. To detect such semantic deviations, this component presents a differential testing framework that systematically compares independent implementations by generating inputs targeting potential divergence points derived from grammar-based specifications. The framework uncovered multiple previously unknown parsing vulnerabilities in widely used open-source software, demonstrating its effectiveness in identifying semantic inconsistencies beyond conventional fuzzing capabilities.
Together, these contributions extend fuzzing beyond standard coverage-based exploration toward deeper semantic understanding and specification conformance. By integrating automated harness generation, fine-grained semantic guidance, and differential analysis, this work advances the precision and applicability of fuzz testing, ultimately improving the robustness and security of modern software systems