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Determining the surface ground state in YbB6 and developing ultra-sensitive nanoscale dissipation measurements in scanning probe microscopy
No full textMy Ph.D. research comprised two main focuses: (1) the analysis of surface states in YbB6 using scanning tunneling microscopy (STM) and spectroscopy (STS) to determine its ground state and resolve discrepancies in angle-resolved photoemission spectroscopy (ARPES) measurements, and (2) the design and construction of a novel scanning probe microscope (SPM) to expand the lab’s capabilities from STM into ultra-sensitive atomic force microscopy (AFM) for both force and dissipation studies.
The first chapter provides an introduction and overview of the STM and AFM techniques and their implementation. Chapter 2 presents my work on YbB6, which is published in its entirety as:
Aaron Coe, Zhi-Huai Zhu, Yang He,Dae-Jeong Kim, Zachary Fisk, Jason D. Hoffman, andJennifer E. Hoffman, “Nanoscale Conducting and Insulating Domains on YbB6,” Physical Review Letters 134, 236205 (2025).
ARPES measurements have disagreed on the ground state of YbB6 on the (001) surface. This discrepancy arises largely from the complex surface structure, caused by the absence of a natural cleavage plane and the presence of polarized terminations. Together these effects produce a disordered surface with nanoscale variations in band bending. As a result, the band structure appears smeared in spatially averaging techniques, and spectral features vary across the surface and over time. Anatomically resolved technique is therefore required to identify pristine terminations and determine their elemental identity. Using STM/STS, we achieved this and proposed a ground state incorporating Rashba spin-splitting that reconciles the conflicting ARPES results.
The third chapter describes the development of a novel millikelvin SPM implementing STM and two AFM modalities. The most intriguing emergent behaviors of quantum materials are determined not only by their static band structure, but by the dynamics of their quasiparticle interactions. For example, various quantum critical fluctuations may drive unconventional superconductivity, while spin fluctuations may drive exotic topological phases. Such dynamics are largely invisible to conventional scanning tunneling microscopy (STM), while ultrafast optics typically average over the spatial variations that are common to strongly correlated materials. We have developed a unique scanning probe microscope (SPM) combining STM and pendulum atomic force microscopy (pAFM) operating below 100 mK in magnetic fields up to 14 Tesla. Atomic-scale fluctuation-dissipation dynamics are quantified by local shifts in resonance frequency (reflecting tip-sample force) and quality factor (indicating dissipation) of a scanned cantilever oscillating like a tiny pendulum above the sample. Our pAFM flexibly employs a qPlus sensor with custom cryogenic preamplifier, or an optically detected soft-silicon cantilever for improved force and power resolution. This manuscript is in preparation.Physic
The Hillock: A Newly Discovered Regenerative Epithelial Structure in the Airway Epithelium
No full textIn 2018, the Rajagopal lab identified the airway hillock, a novel murine airway epithelial structure of unknown function. Hillocks have since been reported in human airways, suggesting that they are an evolutionary conserved structure. Most of the airway is covered by pseudostratified epithelium, composed primarily of basal cells, secretory club cells, and ciliated cells. The hillock is distinguished from this epithelium in three major ways: (1) the presence of stratified-appearing layers of flat KRT13+ cells which sit atop hillock basal cells that are KRT14+ (2) the lack of luminal ciliated cells, and (3) the enhanced replication of the basal cells. Using Cre-ER based lineage tracing of the hillock reporter gene Krt13 combined with immunostaining, we found that hillocks persist for months and have a unique population of basal stem cells that express genes associated with barrier function and cell adhesion. Indeed, using a basal stem cell specific lineage reporter driver (P63Cre-ER), we discovered that the underlying hillock basal stem cells continually replenish overlying squamous barrier cells. In terms of their previously unknown functional role, we found that hillocks resist a remarkably broad spectrum of injuries, including toxins, infection, acid and physical injury because hillock squamous cells shield underlying hillock basal stem cells from injury. Indeed, using mosaic reporter mice, we found that after naphthalene injury, hillock basal stem cells are capable of massive clonal expansion that is sufficient to resurface denuded airway and eventually regenerate normal airway epithelium with each of its six component cell types. Thus, hillocks are a specialized structure that are a injury-resistant reservoirs of plastic stem cells to regenerate the epithelium post-injury.
Additionally, we investigated the regulation of these stem cells in both in vivo and in vitro contexts. Using in vitro air-liquid interface (ALI) culture systems where we can grow airway epithelium from isolated basal stem cells, we found that hillock basal stem cells preferentially stratify and keratinize in the setting of retinoic acid signaling inhibition, a known cause of squamous metaplasia. Indeed, using the in vivo squamous metaplasia model of vitamin A deficiency, we show that mouse hillock expansion is the cause of vitamin A deficiency-induced squamous metaplasia. The existence of hillocks reframes our understanding of airway epithelial regeneration. Furthermore, we show that hillocks are one origin of ‘squamous metaplasia’, which is long thought to be a precursor of lung cancer.Biological and Biomedical Science
Reading the Epigenome: Applications and Innovations in Chromatin Profiling
No full textThe regulation of cell identity is encoded in the chromatin landscape long before transcriptional programs become apparent. However, our ability to interpret and engineer this code has been limited by gaps in mechanistic understanding, a lack of comprehensive reference maps, and the resolution constraints of current technologies. This dissertation establishes a foundational framework for epigenomics across these three dimensions. First, to uncover the mechanistic barriers to cell engineering, we investigate chromatin remodeling during hepatocyte-to-biliary reprogramming. We demonstrate that this lineage conversion is epigenetically incomplete and identify the histone acetyltransferase HBO1 as a critical barrier to plasticity; its depletion enables full lineage conversion. Second, to decode the regulatory logic of lineage specification, we construct a high-resolution CUT&RUN atlas of the mouse immune system. This resource resolves lineage-specific and shared chromatin programs, providing a "regulatory guidebook" for understanding priming, memory, and bivalency across hematopoietic lineages.
Third, to bridge the gap between tissue context and chromatin state, we introduce Photoselective Sequencing (PSS), a method that links spatial information to local epigenetic patterns within complex tissues. Finally, to push the limits of resolution, we describe a single-cell profiling approach that combines expansion microscopy with scCUT&Tag to achieve high-resolution mapping of histone modifications alongside cellular morphology. Collectively, these studies illustrate how new experimental and computational strategies are reshaping our understanding of chromatin dynamics, moving the field from static observation toward the rational engineering of cell fate.Biological and Biomedical Science
Essays on the Effects of Labor Market Change on Workers, Students, and Families
No full textThis dissertation contains a series of essays that explore various ways in which labor market change affects people in their roles as workers, students, and household members.
The first chapter studies how workers are affected by job displacement. Layoffs are a recurring feature of a dynamic economy. Prior research has used administrative records and survey data to document that layoffs impose large adjustment costs on displaced workers, and that these costs vary depending on labor market conditions around the time of the layoff. Compared to those established data sources, online resume data have the potential to provide richer and more timely insight into these adjustment costs for a larger number of workers. This chapter explores that potential. Based on the full list of advance notices of mass layoffs issued in California between 2014 and 2024, I identify establishments and workers who were exposed to one of these mass layoffs among a sample of 62 million LinkedIn profiles. Layoff events have a large effect on establishment size as measured in the LinkedIn data. I characterize the job transitions of workers who leave affected establishments around the layoff event along a rich set of measures, and estimate how their job transitions vary by occupational labor market size and the amount of competing labor supply at the time of the layoff. Workers laid off into less favorable labor market conditions are less likely to make an upward career transition, more likely to move to a new metro area, and more likely to enroll in a degree or certification program in response to the layoff.
The second chapter, co-authored with Joshua Goodman, studies how higher education enrollment in the United States responds to labor market conditions. Declining college enrollments over the past 15 years have triggered questions about the health of the postsecondary sector. Using institution-level data, we make four points. First, such declines are driven not by the four-year sector but by two-year community colleges, which have apparently shrunk by over 30% since the peak of the Great Recession. Second, over one-third of this apparent decline is an artifact of some community colleges being reclassified as offering four-year degrees. Third, pre-Great Recession data shows a 1 percentage point increase in the local unemployment rate increases first-time community college enrollment by 2 percent, suggesting many students are on the margin between community college and job opportunities. For-profit college enrollments are similarly countercyclical, while public and private four-year college enrollments appear acyclical. Our estimates suggest that strengthening labor markets explain about 60% of the post-Great Recession decline in first-time community college enrollment. Fourth, students whose enrollment decisions are most sensitive to labor market conditions appear unlikely to have completed a degree. Though declining community college enrollments are a challenge for postsecondary institutions, it is less clear whether they signal a problem for students on the margin of enrollment.
Finally, the third chapter, co-authored with Clara Chambers and Benjamin Goldman, studies how gender disparities in labor market and education outcomes are affecting marriage and family formation in the United States. Over the past half-century, U.S. four-year colleges have shifted from enrolling mostly men to enrolling mostly women, while the economic position of non-college men has weakened markedly. We examine how these changes correspond with the evolving structure of marriage markets across cohorts and places. As college men have become increasingly scarce, college women have maintained stable marriage rates by marrying high-earning non-college men. This shift—combined with the broader economic decline of non-college men—has sharply reduced the pool of economically stable partners available to non-college women: the share of non-college men who earn above the national median and are not married to college women has fallen by more than 50%. Cross-area evidence shows that education gaps in marriage are smaller where non-college men face lower rates of joblessness and incarceration. Taken together, the evidence suggests that deteriorating outcomes for men have primarily undermined the marriage prospects of non-college women.Public Polic
Noradrenergic Modulation of an Amygdalo-thalamic Circuit
No full textEmotional and cognitive processing rely on communication between the basolateral amygdala (BLA) and the medial prefrontal cortex (mPFC). The BLA regulates mPFC both directly and indirectly via the medial sub-division of the medial dorsal thalamus (MDm). Although the BLA projection to MDm has been established anatomically, less is known about the functional properties of this synapse. Here, using patch-clamp electrophysiology and optogenetics in ex vivo mouse brain slices, we found that BLA neurons make potent synaptic connections onto MDm neurons capable of evoking action potentials. The site of this BLA input overlaps with strong innervation from locus coeruleus norepinephrine (NE) axons. We found that NE acts via α₂-adrenergic receptors to strongly reduce excitatory postsynaptic currents from BLA to MDm. NE also decreases the release probability of BLA axon terminals through a presynaptic mechanism. Postsynaptically, NE depolarizes MDm neurons and increases their tonic firing rates. These findings show that NE, whose levels are elevated during arousal and stress, can suppress transmission of affective information from BLA into MDm, thereby blunting this potent indirect pathway from BLA to mPFC.Neuroscienc
Geomechanical modeling of ground surface deformation related to thrust and reverse fault earthquakes
No full textThrust and reverse fault earthquakes show complex patterns of surface fault rupture that pose substantial hazards to critical infrastructure, including buildings, energy production and transmission facilities, telecommunication systems, and other facilities. These scarps are often highly variable along-strike, with a range of geomorphic expressions from smooth monoclinal profiles to pop-up structures and even highly localized direct fault displacements. To properly design and protect our critical infrastructure, we need the ability to forecast specific ground deformation characteristics, which has proven a challenge given the wide range of possible fault scarp morphologies. There is a paucity of historical earthquakes with surface rupture measurements, limiting our ability to make accurate forecasts based simply on empirical approaches. Thus, this dissertation develops a physics-based approach to model this phenomenon that evaluates a range of geological site conditions – including fault and sediment properties – using numerical modeling techniques to develop a statistical suite of potential ground surface deformation characteristics associated with thrust and reverse fault earthquakes.
We use the distinct element method (DEM) to model the near-surface coseismic deformation observed in thrust and reverse fault earthquakes. DEM is a deterministic modeling approach that is highly effective at reproducing the behavior of fault systems and the granular mechanics of soils and sediments in the shallow subsurface, making it especially well-suited for simulating geologic processes associated with ground surface rupture during large earthquakes. DEM treats aggregate materials as collections of circular disks (in 2D) or spheres (in 3D) that can move independently, with mechanical interactions governed by elastic and frictional contact laws that allow for complex elastic or pseudoplastic behavior. The particles can be bonded together using various contact bond models (we use the parallel-bond contact model) to impart cohesion, tensile strength, and other mechanical micro-properties which approximate natural soil and sediment mechanics. The models deform based on the displacement of boundary conditions at a prescribed velocity and timestep. This approach enables DEM to capture the emergence and evolution of structures like fractures, secondary faults, flexural slip surfaces, folds, and to realistically model sediment deposition, compaction, dilation, and deformation. By varying input parameters such as particle packing density and strength, DEM simulations can evaluate a wide range of natural geologic and soil properties, providing valuable insight into both faulting processes and granular mechanics in sediments and soils.
Chapter 1 explores an initial suite of 2D DEM experiment across a select group of fault dips and sediment strengths to evaluate a range of surface deformation characteristics observed in thrust and reverse fault earthquakes. We calibrated the 2D DEM models to analog sandbox fault models in Cole & Lade (1984) as well as the 3D DEM models from Garcia & Bray (2018a,b). We performed 45 total models which explore shallow (20º), moderate (40º), and steep (60º) fault dips in weak, moderate, and strong sediment that is 5 m deep above bedrock. The key findings of this initial suite of 2D DEM models reveal that numerical models can replicate the natural, geomorphic characteristics of fault scarps. Additionally, we propose a classification of fault scarp morphologies for the 3 main geometries observed in the models: 1, monoclinal scarps; 2, pressure ridge scarps; and 3, simple scarps. Monoclinal scarps form a single, inclined dip panel at the surface. Pressure ridge scarps form backthrusts that contribute to additional uplift above the flat surface of the hanging wall block in a “pop-up” structure. Simple scarps represent a direct fault displacement that is indicative of the fault dip at depth, generating a scarp overhang. Each of these scarp morphologies were represented by unique geomorphic characteristics that could be subsequently modified via hanging wall collapse. Collapse modified features include tensile fracturing at the crest of the scarp that forms blocks of colluvium that gravitationally collapse down the scarp face. The surface deformation characteristics of the scarp height, deformation zone width, and scarp dip were measured every 0.5 m of slip up to 5.0 m of total displacement in the models. This dataset revealed that each of the scarp classes have quantifiable geomorphic characteristics that could improve seismic hazard assessments based on geological site conditions.
Chapter 2 explores the same initial suite of 45 2D DEM models to train a machine learning script that measures the model results with higher accuracy and resolution than the previous 0.5 m of slip. This machine learning script was based on computer vision (CV) script packages and used object detection to identify the key geomorphic characteristics of fault scarps and automatically differentiate between scarp classes. From this classification system, measurements of the surface deformation characteristics (SDC) such as the scarp height (Us), uplift above the flat surface of the hanging wall (Us – Ud), deformation zone width (DZW), and scarp dip were obtained every 0.05 m of slip. We applied this machine learning script to significantly increase the number of SDC measurements by an order of magnitude, yielding 100 measurements per DEM model.
Chapter 3 expands the initial suite of 2D DEM models to examine the influence of additional model parameters and support statistical analyses of ground surface deformation characteristics and geomorphic expressions of fault scarps in thrust and reverse fault earthquakes based on local geological site information. Specifically, we tested 2,459 experiments of homogeneous sediment strengths and 975 experiments of heterogeneous sediment strengths in dense, medium-dense, and loose sediment for depths of 3, 5, and 10 m above a planar fault that dips between 20º and 70º. The hanging wall of the fault in these models displaces up to 5.0 m at a continuous rate of 0.3 m/s. For homogeneous sediment strengths, we evaluated a range from weak to strong sediment in 5 increments that vary the cohesive and tensile strengths of the contact bonds. We also varied the cohesion and tensile strength relative to one another for a total of 13 options. For the heterogeneous sediment strengths, we assessed vertical strength gradients where the base is stronger than the uppermost layers in uniform increments, vertically randomized sediment strengths, and a cohesive top unit above moderate strength sediment. This resulted in a total of 3,434 2D DEM experiments and 346,834 SDC measurements taken every 0.05 m of slip using the same machine learning model as described in Chapter 2. We performed a statistical analysis of ground surface deformation patterns in conjunction with model input parameters to correlate geological site conditions with resultant fault scarp morphologies. We found that the most influential parameters on the patterns of ground surface deformation are the accumulation of slip on a fault, fault dip, sediment depth, and sediment strength. We directly compare these measurements of SDC to historic earthquake ruptures from established fault rupture databases – such as the Fault Displacement Hazards Initiative (FDHI) – as well as the 1952 M7.8 Kern County, California earthquake (Buwalda & St. Amand, 1955). The DEM results effectively describe the range of historic surface rupture observations in these datasets, with improved fits obtained by incorporating additional information about the earthquake size (slip), fault geometry, and surface deformation style. Based on these results, we propose that this dataset can supplement the surface rupture measurements in FDHI and help forecast potential patterns of future surface rupture hazards given specific site characteristics.
Chapter 4 extends the modeling to three-dimensions and examines along-strike variability of fault scarps in thrust and reverse fault earthquakes. Thrust and reverse fault earthquakes are inherently complex and often show significant along-strike variability in the geomorphic expression of the fault scarp, although the geological conditions that yield this variability are largely unknown. Thus, we developed 18 3D DEM models to investigate the influence of fault dip and sediment strength on the along-strike variability of fault scarps. We tested fault dips of 20º, 40º, and 60º for weak and strong sediment and a case where the fault dip varied along-strike from 20º to 70º in 1º increments. Additionally, we performed a case study of randomized sediment strength heterogeneities. These 3D models successfully reproduce main fault scarp types – monoclinal, pressure ridge, and simple – aligning with surface rupture characteristics previously identified in 2D modeling. Our key results showed that the fault dip primarily determined the scarp class whereas variations in the sediment strength, specifically the randomized heterogeneities, influenced the geomorphic characteristics of scarps within that scarp class. Overall, the 3D models support the relationships of ground surface deformation characteristics (scarp class, width, height) established in previous 2D DEM results and replicate measurements of historical earthquake scarps from the Fault Displacement Hazards Initiative (FDHI) and SUrface Ruptures due to Earthquakes (SURE) datasets. These 3D DEM models provide insights into how fault dip and sediment strength govern along-strike transitions in fault scarp morphology. We propose that the combination of 2D and 3D DEM model results can aid Fault Displacement Hazard Assessments (FDHA) and infer patterns of surface ruptures based on local geological site conditions.
Chapter 5 extends the initial suite of 3D DEM models to evaluate the influence of faulting and sediment parameters on the along-strike geomorphic variability of fault scarps observed during thrust and reverse fault earthquakes. We performed 81 3D DEM experiments which explored 4 main model cases: 1, a planar, cylindrical dipping fault at depth; 2, variable fault dip along-strike from 20º to 70º; 3, variable fault seed length along-strike of a planar, dipping fault; and 4, rotating the fault relative to the slip orientation to induce slip obliquity by 30º, 45º, and 60º. We evaluated both homogenous and heterogeneous sediment strengths in a dense sediment assemblage that is 3 m deep. The homogeneous sediment strengths considered weak, moderate, and strong sediment while the heterogeneous sediment assemblages tested randomized heterogeneities and a cohesive top unit. These experiments revealed that uniform, planar faults in homogeneous sediment produce cylindrical (or symmetrical) fault scarp morphologies with little to no variability along-strike. In contrast, variability in the fault dip yielded significant changes in the scarp class along-strike from pressure ridges to monoclinal scarps and simple scarps. This reinforces the conclusion that fault dip plays a primary role in determining scarp class, while the sediment strength influences the style of geomorphic characteristics within the given scarp class. The increasing slip obliquity models converge on the geomorphic expressions of strike slip style faults with increasingly smaller deformation zone widths. We compared the SDC measurements from the 2D and 3D DEM models to measurements of natural surface ruptures in historical earthquakes in the FDHI and SURE datasets. We find that the DEM models effectively capture the range of observed scarp heights and deformation zone widths from historical ruptures and fill the gaps in our understanding from limited historical earthquake events. Furthermore, the geomorphic features of distributed fracturing, splays, backthrusts, and blocks of colluvium that vary along-strike in natural surface ruptures (such as the 1999 Chi-Chi, Taiwan, 2008 Wenchuan, China, and 2013 Bohol, Philippines earthquakes) are replicated in these 3D DEM models such that individual geological site conditions can effectively be modeled in the DEM space. Therefore, we can forecast the potential patterns of future ground surface deformation using local geological site conditions.
Ultimately, we propose that these 2D and 3D DEM models can supplement current FDHA datasets to better inform forecasts of anticipated ground surface deformation for given geological site and faulting conditions using both deterministic and probabilistic approaches. This capacity to forecast future surface rupture characteristics significantly improves available seismic hazard assessments and aid efforts to mitigate the loss of critical resources and sensitive infrastructure systems.Earth and Planetary Science
Characterization of a Novel Vesicular Protein of the Pancreatic Beta Cell
No full textType I diabetes results from the autoimmune destruction of pancreatic beta cells, leading to chronic hyperglycemia absent lifelong exogenous insulin treatment. Cell replacement therapy from stem cell derived beta cells offers a promising therapeutic avenue, by restoring endogenous insulin signaling, and a virtually unlimited supply of beta cells for basic science. It is unclear to what degree other beta cell proteins are involved in regulating glucose metabolism. We describe here ERseq08, identified in the lab by a novel sequencing technique, endoplasmic reticulum sequencing (ERseq), indicating the presence of its transcript in beta cells and positioned it as likely secreted from the same vesicles as is insulin. We examined the nature of the protein, determining that its expression pattern is limited to beta cells and other rare endocrine populations, identified the short isoform predominantly expressed, and observed increased expression in more functional beta cell populations. At the protein level, ERseq08 is present in insulin vesicles. We observe homozygous lethality in three separate loss of function alleles. Investigation of this phenotype revealed mild metabolic and secretory defects in the pancreas and liver of neonatal mutants. We also developed and explored a beta-cell specific overexpression allele but observed no significant changes to whole body metabolism with this expression system.Biological and Biomedical Science
A Unified Framework for Collaborative Knowledge Graph Construction, Editing, and Distribution
No full textKnowledge graphs (KGs) have emerged as a critical technology for grounding artificial
intelligence systems in structured facts, offering a solution to the hallucination and relia-
bility issues plaguing large language models (LLMs). Despite their utility, the infrastruc-
ture required to construct, store, version, and collaboratively edit large-scale KGs remains
fragmented. Previous work has addressed individual aspects of graph management but
has failed to provide a unified, version-controlled ecosystem that supports the property-
rich graphs required by modern applications. To address this infrastructure gap, this thesis
introduces a comprehensive framework comprising four integrated systems: Optimus,
a reproducible pipeline for graph construction; Diamond, a novel lossless binary com-
pression format; GitGraph, a semantic version control system; and GraphEnv, an en-
vironment for multi-agent collaboration. We implemented this framework to enable the
end-to-end lifecycle of graph development, from initial data ingestion to downstream appli-
cations. We utilized Optimus to construct OptimusKG, a biomedical KG with 192,307
nodes, 21.5M edges, and 88.6M properties, demonstrating a 56.5% reduction in build time
through parallel execution. To address storage bottlenecks, we developed the Diamond
algorithm, which we benchmarked against standard formats, achieving a 34×compression
ratio on the popular PrimeKG dataset while preserving all node and edge properties. Fur-
thermore, we formalized the theory of graph versioning by developing a three-way merge
algorithm that allows for semantic, structure-aware conflict resolution, enabling true dis-
tributed collaboration. Finally, we integrated these tools into GRENCE, a clinical decision
support application that uses our infrastructure to ground LLM reasoning in verifiable
medical data. This work establishes a robust software engineering foundation for KGs,
transforming them from static artifacts into dynamic, evolving knowledge stores that can
be efficiently maintained by hybrid teams of human experts and autonomous agents.Computer Scienc
Exocrine Pancreas Cell Plasticity in Injury, Regeneration, and Precancerous Initiation
No full textThe pancreas poses challenges for single-cell transcriptomic profiling due to acinar cell production of digestive enzymes, resulting in underrepresentation of critical cell types. To overcome this, we developed FixNCut, a reversible fixation method that uses dithiobis(succinimidyl propionate) (DSP) to preserve transcriptomes, enabling high quality single-cell profiling of the pancreas. We applied FixNCut to understand pancreatic cancer initiation and exocrine pancreas diseases known to increase risk of pancreatic cancer, including acute, recurrent, and chronic pancreatitis. We identified a conserved transcriptional program of acinar plasticity, termed acinar-to-ductal metaplasia (ADM), across these diverse pancreatic stressors. We characterized ADM states, including a transitional gateway state (gADM), and uncovered PanIN heterogeneity including populations with classical- and basal-like gene expression profiles emerging prior to tumor formation. Immune profiling revealed an initial inflammatory response to acute pancreatitis in the wildtype and oncogenic Kras context. However, oncogenic Kras uniquely triggered a second wave of inflammation, marked by proinflammatory neutrophils, activated macrophages, fibroblast reprogramming, and regulatory T cell emergence, fostering a precancerous niche. Together, we provide a comprehensive atlas of pancreatic cellular plasticity, identifying conserved pathways and novel cell states linked in injury, regeneration, and cancer initiation.Medical Science
Very Early Lithic Technology at the Mount Merino Site: A High-Grade Chert Quarry in The Hudson River Valley of Northeastern North America
Get PDFAbstract
The motivation for this research was to locate Ice Age stone tool manufacturing
sites in the Hudson River Valley. The Mount Merino site is a high-grade source of chert
that early cultures would need for tool production and displayed potential for early lithic
assemblages to be located. One goal of this research was to investigate the site and
determine the lithic techniques that were used there. Little research has been conducted in
northeastern North America regarding this subject.
Initially, the antiquity of the Mount Merino site was thought to be from the Clovis
culture, based on the manufacturing techniques of the bifaces found at the site. The people
at the Mount Merino site produced their bifaces in the same manner as the Clovis culture.
A strong blade and blade core technology was present at the Mount Merino site, which is
also a trait of the Clovis culture.
The artifacts that were found during the archaeological excavation of the site have
proven to be unlike any other cultural material discovered from the glaciated portion of
northeastern North America to date. The assemblage differs from the Clovis culture in one
main aspect: not one of the bifaces found at the Mount Merino site exhibited fluting or
early-stage proximal end thinning, which had been used by the Clovis people. This is an
important discovery which differs from any archaeological assemblage previously
recorded from the region of northeastern North America.Extension Studie