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    Laurentide Ice Sheet dynamics across multiple glacial-interglacial cycles from Quaternary stratigraphic records in the western Hudson Bay Lowland, central Canada
    (University of Waterloo, 2026-01-29) Hodder, Tyler
    Understanding the terrestrial Quaternary stratigraphic record is necessary to reconstruct regional- to continental-scale paleo-ice sheet fluctuations and compare how these events relate to oxygen isotope proxies derived from marine sediments, sea level change, and contemporary ice sheets. Regions that contain an extensive stratigraphic record beyond the last glacial maximum are key to understanding the long-term behaviour of ice sheets and provide field-based constraints for ice-sheet reconstructions and modelling. The Hudson Bay Lowland (HBL) is one of these key regions situated in central Canada that contains a fragmented stratigraphic record of at least the last four Laurentide Ice Sheet (LIS) glaciations. The main objectives of this thesis are to 1) reconstruct the spatio-temporal evolution of the LIS from the Quaternary stratigraphic record of three relatively understudied regions of the western HBL and 2) determine the timing and climate conditions that persisted during ice-free periods across multiple glacial-interglacial cycles. To better understand the fragmented stratigraphic record that is dominated by glacial sediments (till), this thesis developed a hybrid lithostratigraphy-allostratigraphy approach that relies on multi-parameter characterization of tills to establish sediment provenance and the ice-flow direction that deposited the sediment. This included detailed study of 70 sections, the collection of 193 stratigraphic ice-flow indicators (154 till fabrics and 39 lodged clasts) and analysis of 393 till samples. Once the till framework was established, the relative age of each nonglacial bed was then determined using the bounding surfaces of designated till units. At least 18 units have been identified this way and correlated across the western HBL. The nonglacial beds were further characterized to assess the timing of sediment deposition using radiocarbon and optical dating methods and paleo-environmental conditions that existed using pollen and foraminifera analysis. Lastly, stratigraphic frameworks presented herein did not rely on geochronology constraints to anchor correlations and the age of identified interglacial beds can be further tested to confirm the age of interglacial beds. The new stratigraphic framework for the western HBL provides important field-based constraints for LIS reconstructions. This includes evidence that there was asynchronous growth of the two major domes of the LIS during the last two glaciations, with accelerated early growth of the Quebec–Labrador Dome relative to the Keewatin Dome. In each glaciation, the Keewatin Dome becomes more active relatively later in glaciation and persists until deglaciation. During the last glaciation, ice-flowing from the Keewatin Dome likely did not occur until MIS 2 and this S-trending ice-flow transitions into late-glacial SW-trending ice-streams. During the penultimate glaciation (~MIS 6), till deposition by S- to SW-trending ice was extensive and one of the main ice-flow events across the western HBL when the Keewatin Dome was likely situated in northern mainland Nunavut. Furthermore, during deglaciation the Keewatin Dome or an ice divide was likely situated in the western HBL. There is widespread evidence across the western HBL that sediments belonging to at least three pre-Holocene interglacial periods exists, which provides an important archive to understanding past climatic conditions in central Canada. For two of these interglacials there is evidence of marine inundation which likely occurred during Termination II (~130 ka) and Termination III (~243 ka). In the Churchill River region, the marine limits for both marine incursions are higher compared to the Tyrrell Sea (Holocene) marine limit, providing important field-based constraints for LIS modelling. Importantly, new age estimations from the uppermost intertill nonglacial sediments, combined with consideration of the paleobotanical datasets in the western HBL stratigraphic record, suggest that the region was last deglaciated during MIS 5e. This implies that the HBL, and likely Hudson Bay, remained glaciated during MIS 3. The presence of weathered bedrock within the western HBL indicates that glacial erosion of bedrock was negligible in places during the Quaternary Period. Relict landscapes across northeastern Manitoba, such as preserved streamlined landform flowsets that are situated outside the margins of late-glacial ice streams, provide evidence of limited erosion following initial glacial advance into the area. The results of this thesis have provided an updated Quaternary stratigraphic framework for the western HBL, a key region for understanding the long-term evolution of the LIS. The Quaternary stratigraphic record is highly fragmented, which reflects patchy erosion and deposition over multiple glacial-interglacial cycles of the region. The new stratigraphic frameworks developed provide an increased understanding of the growth, evolution and retreat of the LIS during the past two glaciations and insights into pre-Illinoian glaciations, which are essential to improving reconstruction and modelling of the ice sheet throughout the Middle and Late Pleistocene.
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    Correlation-Aware Rendering: Improving Sampling and Denoising for Realistic Image Synthesis
    (University of Waterloo, 2026-01-29) Zhou, Weijie
    In realistic image synthesis, Monte Carlo integration is the foundation of most rendering algorithms, but it inevitably introduces noise. To reduce such noise, advanced sampling strategies—such as Markov chain Monte Carlo (MCMC), resampled importance sampling (RIS), and modern denoising techniques—have been proposed. However, these methods of ten introduce correlations that can manifest as new artifacts. This thesis investigates three distinct research directions, spanning from mitigating correlation to actively exploiting it. The first direction tackles correlation in MCMC methods. Traditional MCMC often suffers from low acceptance rates, producing visually “spiky” noise. We propose combining MCMCwithpathguiding techniques to improve acceptance probabilities, thereby reducing correlation artifact and improving image quality. The second direction addresses correlation artifacts in the widely used Reservoir-based Spatiotemporal Importance Resampling (ReSTIR) algorithm. While ReSTIR achieves ef f icient sampling by reusing samples across pixels and frames, this reuse can lead to blotchy artifacts, as many pixels may end up sharing only a few important samples. Observing par allels between ReSTIR and MCMC, we introduce a new spatiotemporal MCMC framework that replaces reservoir resampling. Applied to both direct illumination and path tracing, our approach significantly reduces correlation artifacts while retaining efficiency. The final direction shifts from reducing correlation to exploiting it. We present a gener alized combination framework that leverages spatial, temporal, and multiscale correlations to reduce error. This method enables robust cross-domain fusion, effectively suppressing systematic artifacts and improving temporal coherence—particularly crucial in animation. Through extensive experiments, we demonstrate that our framework enhances temporal stability, visual appearance, and residual error reduction across diverse rendering scenarios.
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    Towards Secure and Efficient Route Computation for Cross-Chain Message Delivery
    (University of Waterloo, 2026-01-29) Rezaei, Amin
    Demand for blockchain applications has led to a surge of new public blockchains. However, this fragments liquidity and pushes users to bridge across unfamiliar protocols, increasing risk and complexity. Cross-chain communication enables interoperability, allowing contracts to execute logic and move assets across chains. Yet current delivery solutions either support message passing only between directly connected chains, limiting connectivity, or are centralized and route through a single hub chain that introduces a single point of failure and requires trust in the hub operator. Inter-blockchain communication can become more robust by leveraging concepts from traditional network architectures, including routing, name resolution, and policy-based message delivery. These mechanisms can increase connectivity by enabling chains that are not directly connected to communicate securely over multi-hop routes. This thesis studies the problem of policy-driven cross‑chain routing: Current cross-chain routing is largely ad-hoc and manual, and does not reliably respect users' security or cost preferences when no direct connection exists. Given a dynamic inter‑chain topology and user policies (e.g., security thresholds, fee budgets, latency targets), we compute routes over multi‑hop Inter-Blockchain Communication (IBC) while ensuring (a) security constraints are strictly enforced on-chain and (b) preference constraints (e.g., minimizing gas costs) are met with practical guarantees. This is challenging because the required inputs (e.g., fees, validator sets, congestion, and application-specific state) change independently on each chain, yet the resulting route and its policy compliance must be verifiable on the destination chain at a reasonable cost. We present a modular stack: a Transport Layer with Policy Enforcement Module, a Relayer Control Plane for route computation, and a Relayer Data Plane for execution, which separates concerns between policy specification, route computation, and delivery. We introduce three routing methods: (1) Single‑Relayer routing, which computes routes off‑chain independently by off-chain relayer nodes, (2) zkRouter, which computes routes off‑chain with a succinct zero‑knowledge proof of policy compliance and (3) Relayer Network, a new collaborative overlay that distributes operational load (client updates, packet relaying) across relayers. Our prototypes demonstrate that our stack is practical and achieves higher decentralization, better connectivity, and greater scalability, enabling richer and safer cross-chain applications while preserving IBC’s security assumptions and without significant fee overhead. Our evaluation shows: (1) near 90% connectivity vs. 15% for hub-and-spoke; (2) more than 30% connectivity after removing top four chains, reaching 50% with topology upgrades; (3) less than $0.10 on-chain cost per message; (4) scales to more than 10^6 messages maintaining low processing time.
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    Monastic Diets and Aquatic Species: Examining Potential Fish Consumption at the Ghazali Monastery, Sudan Through Stable Isotope Analysis of Sulphur
    (University of Waterloo, 2026-01-28) Tham, Carita
    Stable isotope analysis can be applied in bioarchaeological contexts as a tool to assess paleodiet as this technique relies on naturally occurring differences in isotopic values in different food sources and environments. Previous research has been conducted to assess possible dietary composition of the monastic inhabitants of at the medieval Makurian site of Ghazali (ca. 680-1275 CE), Nubia using stable isotope analyses of carbon (δ13C) and nitrogen (δ15N) on bone collagen of its monastic inhabitants. This showed a varied diet evidently comprising of both terrestrial plants and animals. Additionally, δ15N values observed in five individuals suggest potential aquatic species consumption in conjunction with terrestrial animal protein. However, no remains of aquatic species were identified during excavations at Ghazali, and little aquatic species were identified at other Makurian sites. This lack of evident aquatic species (e.g. fish) consumption at Ghazali brings forth numerous questions surrounding dietary practices both at Ghazali and within the broader region of similar Makurian monasteries. This research utilized stable isotope analysis of sulphur (δ34S) on human bone collagen in conjunction with previously presented δ15N values, in tandem with existing textual and bioarchaeological evidence from Egypt and Byzantium, to determine the presence or absence of fish in the diet of the monastic inhabitants at Ghazali. The sample consisted of 20 individuals from Cemetery 2, where 18 of these individuals were male monks. Analysis of δ34S, when coupled with previous δ15N values, revealed that four of these individuals showed evidence of possible fish consumption alongside terrestrial animal protein consumption.
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    Jewish Women in the Concentration Camp System in Germany, 1933-1945
    (University of Waterloo, 2025) Koepke, Alicia
    This Master’s Research Paper examines the experiences of Jewish women in the three women’s concentration camps of Nazi Germany: Moringen, Lichtenburg, and Ravensbrück in chronological order from 1933 until 1945. With the exception of various early provisional concentration camps in the early 1930s and women’s subcamps of former men’s camps towards the end of the war, women were largely relegated to one camp at a time (Moringen 1933-1938, Lichtenburg 1937-1939, Ravensbrück 1939-1945). As a result, studying the experiences of these women as they were transferred from one camp to the next throughout the Nazi period allows us to examine how women’s concentration camp experiences evolved and changed over time. In studying specifically the experiences of Jewish women, we see not only how gender, but also race, affected the treatment and experiences of female prisoners in these camps. Ultimately, the three main camps reflect both Nazi policies and social movements which affected how long Jewish women stayed in the camps, the reasons given for their arrest, and how they were treated and categorized within the camps. The secondary focus of this project was to examine life within the camps, how these women reacted to their imprisonment, how they survived months or even years in the concentration camp system, and how they interacted with fellow non-Jewish prisoners. Organized into three main sections (one for each camp examined) with some subsections to focus on particular aspects of each camp, this paper follows the development of the women’s concentration camp system in a chronological order. The lengthy introduction seeks to establish the origins of the Nazi concentration camp system, the particular difficulties in studying Jewish and female prisoners in the earliest camps, the subject of gender in historical analysis, and the available historiography on this topic. The section on Moringen is divided into two parts. The first section deals with the organization of the Moringen concentration camp, including an examination of the available primary sources which discuss the separation of Jewish women into their own “Judensaal” (Jewish Hall). The second section examines daily life within Moringen. Lichtenburg is examined in only one section, both because it served as a women’s camp for just over one year and because there are few sources dedicated to this camp. The final two sections examine Ravensbrück. Part 1 deals with the first period (1939-1942) in which Jewish women were imprisoned in the camp, ending with the final deportations of Jewish women to Auschwitz in the Fall of 1942 after which the camp remained “Judenrein” (“free of Jews”) for a short while. Part 2 on Ravensbrück deals with the late war years in the camp and the declining conditions from 1943 until liberation in 1945 during which thousands of Jewish women entered the camp from eastern camps and ghettos. This paper contributes to the historiography on gender and race in the German concentration camp system by examining both the development of the concentration camp system for women and the particular experiences and daily life and survival of Jewish women from 1933 until 1945.