Dartmouth Institute for Health Policy and Clinical Practice
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C4 grasslands and hominin paleoecology: comparative, functional, and evolutionary perspectives
No full textThis dissertation examines the functional and evolutionary impacts of Plio-Pleistocene C4 grassland expansion in the primate and hominin fossil records. I employ ecological, comparative primatological, and evolutionary modeling approaches to test hypotheses about the impact that shifting C4 resource landscapes had on the paleobiology and evolution of fossil hominins and sympatric fossil monkeys. In Chapter 1, I use a plains bison model system to test the “C4 challenge” hypothesis, which argues that C4 grasses pose unique mechanical demands for herbivore consumers that would require specialized dental adaptations to process. I find mixed support that C4 diets pose unique foraging challenges relative to C3 vegetation, with only the C3 forb to C4 grass transition being most impactful from a functional standpoint. In Chapter 2, I test the performance impacts of postcanine tooth enlargement in a forest primate community model system in West Africa, with the aim of modeling the functional consequences of postcanine enlargement during C4 expansion for some fossil hominin taxa (e.g., Paranthropus). I find that larger teeth promote increased chewing performance across the community, with the highest chewing performances being found in those primates that consume the hardest and toughest food objects. In Chapter 3, I utilize stable carbon and strontium isotope data to reconstruct the C4 foraging paleoecology of fossil Theropithecus, a lineage of large grassland monkeys contemporaneous with many fossil hominin species. I find that their greater commitment to C4 graminivory over the course of the Plio-Pleistocene was associated with a shift from selective graminivory with smaller body sizes to bulk-feeding graminivory with larger body sizes, a seemly stable strategy that shifted to an evolutionary trap as increasing seasonality made elevated ranging costs untenable to sustain. In Chapter 4, I fold in stable carbon and oxygen isotope data from fossil hominins and monkeys across the Plio- Pleistocene period to test the pillars of behavioral drive hypothesis, showing that rapid behavioral shifts in graminivory in both fossil hominins and Theropithecus proceeded attendant changes in dental morphology by ca. 700,000 years. I then utilized a novel comparative approach with oxygen isotopes to disambiguate the graminioid tissues contributing to behavioral drive
The genetic basis of male Drosophila attraction to female 7,11-HD pheromone
No full textMale Drosophila possess chemosensory receptors to detect contact pheromones which sometimes incite courtship rituals consisting of an extension and vibration of a wing, producing a species-specific courtship song whose length scales with the male’s level of attraction.1 The pheromone 7,11-heptacosadiene (7,11-HD) is a cuticular hydrocarbon pheromone expressed on female D. melanogaster (D. mel) but not on D. simulates (D. sim), causing D. mel attraction and D. sim aversion. This study aimed to quantify male’s attraction to 7,11-HD among different strains of D. mel and D. sim. To do so, virgin D. sim females, known to not produce 7,11-HD, were perfumed with controlled amounts of synthetic 7,11-HD and used to standardize visual stimuli in the promotion of courtship behaviors. Virgin D. mel and D. sim males were collected and each was paired with a single perfumed female. Courtship behaviors were recorded for 30 minutes, and SongTorrant software was used to record visual and audio data of fly tapping and wing song.3 A combination of SongExplorer software and R code utilized machine learning to identify the different components of the fly song and quantify total singing time. The singing time was quantified onto a courtship index and plotted against the concentration of pheromone on the female. The neutral to positive slopes found with D. mel males indicate stable or increased attraction while the neutral to negative slopes of D. sim males indicate absent or reduced attraction to females with higher levels of 7,11-HD.https://digitalcommons.dartmouth.edu/wetterhahn_2025/1012/thumbnail.jp
A multi-proxy reconstruction of environmental conditions during Termination 1 in central New Hampshire
Get PDFThe collapse of the Northern Hemisphere ice sheets subsequent to the Last Glacial Maximum (~26-19 ka) marked one of the largest natural climate change events in recent time. In response to global warming, the Laurentide Ice Sheet (LIS), the ice sheet that covered much of northern North America, receded almost completely during a time known as “Termination 1” (~19-11 ka). The climate changes during this time also caused significant changes in landscape morphology, ecology, and the lifeways of indigenous peoples. This project characterizes the timing of deglaciation and major post-glacial landscape changes across New Hampshire using lake sediment cores. I developed new sediment records from three lakes in central New Hampshire using proxies including visual stratigraphy, radiocarbon dating, loss on ignition, and magnetic susceptibility. I also compiled stratigraphic, radiocarbon, and lithologic proxy data from 19 previously studied lakes across New Hampshire and eastern Vermont. From these data, I generated age-depth models for the new and previously studied lakes and used these to determine the timing of deglaciation of the LIS in New Hampshire and the transition from basal clastic sediment to overlying organic sediment, which marks a significant landscape change.
To assess the broader pattern of deglaciation, I compared the lake-based ages of deglaciation with chronologies of deglaciation based on glacial varves (annually laminated pro-glacial lake sediments) and surface exposure dating. The lake-based ages of regional deglaciation range from ~20 to 13 cal ka BP and show a trend indicative of consistent northward retreat of the LIS, similar to that indicated using varve chronology. I determined the timing of clastic-to-organic sedimentation in the three new lakes and 12 previously studied lakes. The age of the sedimentological transition in the lakes has no clear spatial trend, and dates to ~13.8-11.0 cal ka BP. My results provide a better understanding of regional deglaciation and provide insight into the environmental changes associated with the transition from clastic-to-organic sediment
The Long Way Home: A Moment in Time Before Agony Ridge
Get PDFAn encounter with a father and son partway up New Hampshire’s Mount Lafayette suggests how to lead someone with kindness
The Boring Forest ? Canada\u27s Boreal Forest is Actually a Breathing Mass of Life
Get PDFAn archeologist argues that the vast forested region of the Laurentian Plateau holds a soul and value of its own and does not deserve the disparaging attitude some hold toward it
Understanding oncology physician movement and its implications on cancer care teams and patients
No full textNearly 20% of oncology physicians planned to move to new practices or leave practice altogether in 2023, with common stressors related to limited staffing and increased clinical burden. This combination of movement and departures is collectively referred to as turnover. High-quality cancer care relies on access to well-staffed and coordinated clinical teams, and thus, turnover within these teams can compromise care access, delivery, and quality. Prior research within primary care has demonstrated that turnover can result in delayed or worsened care and higher health care spending. However, there are limited studies of turnover within the oncology workforce. Understanding how oncology physician turnover impacts cancer care and care teams is critical for identifying system and team features that promote team resilience and maintain care quality amid workforce changes. The goal of this thesis work was to leverage Medicare claims to measure oncology physician movement and investigate its impact on patients and the remaining care teams. For Aim 1, I created a patient cohort of Medicare beneficiaries diagnosed with breast, lung, or colorectal cancer in 2016 – 2019, which informed an oncology physician cohort based on all medical oncologists, radiation oncologists, and surgeons involved in their cancer care. I identified oncology physicians who moved practices based on changes in their billing location, and assessed characteristics associated with physician- and region-level movement. Aim 2 used annual patient-sharing networks to assess how oncology physician departures impacted the structure of the remaining care team. Aim 3 examined how oncology surgeon departures affected the timeliness of breast cancer surgery. I found that physician connectedness was strongly associated with movement, where highly-connected oncology physicians had lower odds of moving. Oncology physician connectedness also changed after a colleague’s departure. Retained rural-practicing oncology physicians experienced an expansion and restructuring of their patient-sharing ties following a colleague’s departure while urban-practicing physicians experienced a consolidation. Lastly, breast cancer surgeon departures were associated with increased odds of surgical delay among patients with breast cancer. These three aims provide evidence that oncology physician movement can disrupt cancer care and care teams, yet increased collaboration and connectedness may mitigate these effects
ILL
No full textOn 28 September 2024, the narrator of this story, his four-year-old son and wife arrive in Lisbon, where they have decided to spend his sabbatical after eleven years of teaching French at a boarding school in New England. His objective is clear: to heal. For the past two years, his liver has been showing warning signs. Despite all the tests, the doctors are unable to establish a clear diagnosis. The narrator begins to wonder if his failing body is but a reflection of the failing world around him. As he travels across the Atlantic Ocean to Portugal, he remembers a lecture from one of his professors at the Sorbonne in which she mentioned a letter that Dante sent to a cardinal indicating the existence of spiritual cells. Are these cells real or a mere fantasy? The narrator embarks on a journey to find out, convinced that his discoveries might be able to cure him.
“Ill” is a fictional memoir and travelogue set in the year 2028 in which the narrator, back at the boarding school, reconstructs his stay in Portugal. The text meditates on the mechanisms at the heart of human memory and imagination. It is also a project that tries to answer some pressing questions: Do we become an extension of what we build? What sort of illness has taken hold of the Western World and its people? Can we heal? And if so, how? “Ill” offers the voice of a man whose body and mind once tried as hard as they could to find convincing answers to these inquiries
Designing Your Next Read: How Psychology Shapes the Way We Choose Books
No full textDesigning Your Next Read invites students to explore the psychology behind everyday choices through the familiar act of picking a book. Using the lens of design psychology, the lesson examines why decision-making often feels overwhelming and how small shifts in perception, environment, and heuristics can make choices easier and more enjoyable. Students engage in interactive exercises, including a book-browsing activity, mini-lectures on choice biases, and a “Book Blurb” exercise, to reveal how heuristics such as availability, affect, and familiarity shape responses.
Through guided discussion and reflection, students connect psychological theories like the paradox of choice and decision paralysis to their own reading habits and broader consumer experiences. By the end of the session, participants will understand how design and psychology influence decision-making and leave with practical, evidence-based strategies to make reading and everyday choices more intentional, enjoyable, and empowering
Mangroves: A Lesson on Modeling Changing Shorelines
No full textThis lesson is an overview of storm barriers, specifically mangroves and how they maintain shorelines. It is meant to offer a visual experience of coastline protection and provide a background for deeper understanding about intertidal zones and their conservation. Students will spend time creating a solution to a flooding problem by making a mock coast and storm barrier. To wrap-up the lesson, students will pair up, then reflect on their model and then individually write or draw their takeaways
Small Scale Aluminum Anodizing
No full textAnodization is a crucial process of the aluminum manufacturing process that makes aluminum products more durable while also enabling customization with colored anodized dyes. However, for small scale aluminum manufacturers, anodizing is largely inaccessible. Existing solutions either involve outsourcing to large automated warehouses or manually anodizing by hand, both of which suffer from prohibitive disadvantages. Large warehouses are automated but, because they require shipping products and require batches of parts far greater than normal for small scale manufacturers, they have long lead times and are prohibitively costly. Conversely, anodizing by hand is faster and cheaper, but the manual labor required is time intensive and risks unnecessary exposure to hazardous chemicals. The Small Scale Anodizing Gantry takes the best of both worlds by enabling automated anodization in-house. By racking up to 6 kg of small parts and starting an anodizing sequence, owners of the gantry can consistently and safely anodize their manufactured products while working on other more higher value, manual tasks. The gantry is initially programmed with GCODE using a custom designed calibration program called the Anodizing Program and combined with the Open Builds driving software to control it. Its mechanical structure consists of readily available T-Slotted framing with custom gantry plates and a Z-Axis designed to handle an aluminum rack and power supply for anodizing. In collaboration with project sponsors at Lost Nation Research and Development, this gantry is meant to be integrated with their temperature control system that regulates the baths of each chemical in the anodizing process