Showing 271 - 280 of 317 Items
Investigating the Effects of Student Debt on Career Outcomes: An Empirical Approach
Date: 2019-05-01
Creator: Gideon Moore
Access: Open access
- High student debt has been hypothesized to affect career choice, causing students to desire stable, high paying jobs. To test this hypothesis, I rely on plausibly exogenous variation in debt due to a federal policy shift. In the summer of 2007, the Higher Education Reconciliation Act (or HERA) expanded the cap for federally subsidized student loans. I examine how variation in debt affects career choice and eventual salary of students using data from the National Longitudinal Survey of Youth 1979 Child and Young Adult Cohort of students who were of college age during the implementation of the policy. I find that student debt has no impact on salary two years after graduation; however, it does seem to shift students’ career choices, leading some to avoid careers in public service industries such as teaching and social work.
Crazy American
Date: 2022-01-01
Creator: Emma Quan Dewey
Access: Open access
- Crazy American is an evening-length dance solo choreographed and performed by Bowdoin's first Dance honors student, Emma Quan Dewey. This dance is an embodied exploration of her mother's family migration history from South China to the Philippines to the US, and how it places her and her family within structures of US imperialism, racial hierarchies, and Chineseness itself. Based on ethnographic, historical, theoretical, and embodied research, Crazy American examines the intimate ways these structures play out at the level of the body, and seeks to imagine new possibilities for moving through systems and stories of power.
Modeling Oyster Growth Dynamics in FLUPSY Systems to Develop a Decision Support Tool for Seed Management
Date: 2023-01-01
Creator: Gretchen Clauss
Access: Open access
- As the Gulf of Maine warms and lobsters move north to colder waters, Maine’s working water front has begun to diversify. There is a thriving new ecosystem of aquaculturists looking to keep Maine’s waterfront traditions alive in a lasting, sustainable way. One of the most popular aquaculture industries is oyster farming. With an increasing number of oyster farms developing in Midcoast Maine each year, we seek to develop a decision support tool to aid farmers in seed management. Oyster farmers can choose weather or not to use an upweller on their farm, and our goal is to provide guidance on this choice, as well as on upweller management. We begin by culminating and synthesizing data from previous literature and oyster farmers. We then use this data to first build a basic analytical model of a cohort of oysters based on an exponential growth model. We expand this model to include biological differences among oysters as well as management practices. Finally, we walk through a case study, illustrating how our tool could be used to make seed management decisions on an individual farm scale.
The effects of nitric oxide on the modulation of the cardiac system of the American lobster, Homarus americanus, via a peptide (GYSDRNLRFamide)
Date: 2014-08-01
Creator: Sophie Janes
Access: Open access
- The central pattern generator (CPG) is a neural network that controls the rhythmic patterned outputs, which generate locomotion as needed. The lobster provides a good model to study CPGs because it has a relatively simple CPG. The lobster CPG, or cardiac ganglion accommodates for a range of activities and changes in the environment (Cooke, 2002).The small lobster CG is made up of nine neurons that control the neurogenic heart. The lobster CG is located on the inner dorsal wall of the heart and forms long neurites that branch onto the heart muscle. The CG, through an intrinsic mechanism, generates patterned and rhythmic bursts to the heart (Cooke 2002).The H. americanus CG sends information to the heart muscle to regulate the heart beat. The patterned bursts from the CG need to be adjusted in response to changing demands, for example, activity level or blood volume. Two general mechanisms, intrinsic feedback and extrinsic neuromodulation, have been identified to facilitate this adjustment. Through an intrinsic feedback mechanism, the muscle sends information back to the CG via a positive pathway and a negative pathway. In the positive pathway, stretch-sensitive dendrites of cardiac neurons increase the frequency of heart contractions when stretched (Cooke 2002). In the negative pathway, nitric oxide (NO), produced by the cardiac muscle, slows the frequency (Mahadevan et al. 2004). The interplay between the negative and positive feedback pathways regulates the output of the CG. An extrinsic mechanism has also been identified to regulate the CG output. Chemical neuromodulators that are released either locally or as hormones signal to the heart or CG to modulate ganglion activity. The intrinsic and extrinsic mechanisms affect the contraction amplitude and frequency of the heart.Within this simple invertebrate organism, a complex layering of control exists. Studies of the effects of various extrinsic modulators suggest that these modulators may alter how the feedback pathways operate. I examined what effect the neuromodulator GYSDRNLRFamide (GYS), a peptide found in the lobster nervous system, has on the balance between the positive and negative pathways (Ma et al., 2008). Recent experiments have demonstrated that when GYS was applied at high concentrations in the whole heart, the frequency decreased. This suggests that GYS may play a role in the intrinsic feedback pathways, and likely enhances the negative pathway.I looked at if nitric oxide altered the modulation of the heartbeat frequency when enhanced by the extrinsic modulator, GYS. Based on previous experiments, I hypothesized that GYS allows the NO, or negative pathway to predominate. In order to test my hypothesis, I examined the effects of GYS when I removed nitric oxide, which allows the negative pathway to exist. I compared the characteristics of the heartbeat when saline was run through the heart to when GYS was run through the heart. I also compared the characteristics of the heartbeat when the NO inhibitor, L-NA, was applied to when GYS was applied in the presence of L-NA. I finally compared the changes in frequency between these two comparisons. I found a significant difference between the change in frequency of the heart perfused with GYS in saline as opposed to perfused with GYS in L-NA. GYS had a greater negative effect without L-NA. These results demonstrate that NO is likely the cause of the observed decrease in frequency. Final Report of research funded by the Doherty Coastal Studies Research Fellowship.
Characterization of Dissolved Organic Matter in Local Marine and Terrestrial Waters
Date: 2014-08-01
Creator: Anna Bearman
Access: Open access
- There are numerous anthropogenic pollutants present in both marine and terrestrial waters.1 Though many of these chemicals do not absorb light and therefore cannot undergo photolyic degradation on their own, dissolved organic matter (DOM), found alongside pollutants in natural aquatic waters, can act as a catalyst in the attenuating process of contaminants. DOM is a complex mixture of organic compounds derived from decaying plants, animals and microorganisms. Since DOM can absorb light, it can transfer energy to contaminants, allowing them to break into smaller and often less hazardous molecules. The behavior of DOM is largely determined by its functional chemical components, and the character of DOM is constantly changing with the environment. For example, two International Humic Substances Society standards Pony Lake DOM from Antarctica and Suwannee River DOM from Georgia demonstrate very different compositions and characteristics2. More important than simply identifying varying functional groups in DOM these standards, however, may be understanding how our local water in the Androscoggin River and Gulf of Maine behaves and attenuates contaminants. The goal for this project was to first isolate DOM from the Androscoggin River and the Gulf of Maine. DOM was extracted using the Thurman and Malcolm procedure,3 beginning with collection and filtration of water from the Androscoggin River boat launch and Simpson’s Point. The water was then run through a chromatography column, through the method of absorption chromatography the dissolved organic matter sticks to the resin within the column. DOM was then eluted from the column, concentrated, and protonated with an ion exchange column. The resulting concentrated DOM solution was then freeze-dried to obtain the final powdered DOM fraction. Because the quantity of DOM isolated from the Gulf of Maine was too small for characterization, we determined that a new collection method using equipment suited for sampling larger volumes of water will be necessary for future DOM characterization. Instead we focused on collecting samples from the Androscoggin on a weekly basis. Following isolation, the Androscoggin River DOM was dissolved in Type I water to make 3mg/L DOM samples and then characterized through UV-Vis absorption and 3D fluorescence Excitation-Emission Matrix (EEM) spectroscopy techniques. The data was then processed using the parallel factor analysis (PARAFAC) method.4 PARAFAC deconvolutes the fluorescence spectra into the distinct fluorescent components present in the complex DOM mixture (Figure 1). This preliminary analysis indicates that Androscoggin River DOM is made up of at least six specific fluorophores. In the future, I will identify the types of molecules responsible for each component signature and attempt to ascertain the relative concentration of each photoactive constituent in the DOM samples. This information will have significant implications for the photochemistry of natural and anthropogenic chemicals in natural waters. Funded by the Henry L. Grace Doherty Coastal Studies Research Fellowship and James Stacy Coles Summer Research Fellowship in Chemistry.
Impacts of eelgrass (Zostera marina) on pore-water sulfide concentrations in intertidal sediments of Casco Bay, Maine
Date: 2016-05-01
Creator: Sabine Y Berzins
Access: Open access
- Eelgrass (Zostera marina) is a perennial seagrass that provides many vital ecosystem services including stabilizing sediments, maintaining water clarity, and providing complex habitat in the intertidal and shallow subtidal coastline. Historically, Maine supported dense eelgrass beds in shallow waters surrounding islands and along the coastal mainland. However, in 2012, high population densities of European green crabs (Carcinus maenas), which physically disturb and remove eelgrass as they forage, were correlated with widespread eelgrass declines. Over 55% of the area of eelgrass in Casco Bay was lost, mainly between 2012 and 2014. Eelgrass typically grows in low-oxygen sediments that produce a chemically reducing environment. Sulfate-reducing bacteria in these reduced sediments produce hydrogen sulfide, a toxin that can intrude into eelgrass tissues and impair the plants’ ability to photosynthesize. When eelgrass is not present, sulfide can build up in the pore-water. When eelgrass is present, it can oxygenate the sediments through its roots, thereby preventing the intrusion and buildup of toxic hydrogen sulfide. However, if the substrate is de-vegetated, oxygen levels drop as sedimentary organic matter is decomposed, and the accumulation of sulfides to harmful concentrations in the pore-water may make recolonization of eelgrass difficult or perhaps impossible even in the absence of green crabs. In an effort to monitor characteristics of Casco Bay eelgrass beds and determine spatially where eelgrass may be more likely to recover, four Casco Bay sites with varying degrees of vegetation loss were sampled in 2015 for pore-water sulfide concentration, sediment carbon and nitrogen content, and sediment grain size analysis. Measurements of sulfide concentrations showed correlations with the timing of eelgrass loss, such that vegetated sites had low pore-water sulfide concentrations and sites that had been de-vegetated for longer periods of time had high sulfide concentrations. Carbon and nitrogen content in the sediment was higher at de-vegetated sites, likely due to a higher percentage of finer sediments at those locations. Coarser sediments were more highly vegetated than finer sediments, perhaps displaying a preference of green crabs to forage in finer sediments. Catastrophic loss of eelgrass in Casco Bay has likely led to differences in sulfide levels, carbon and nitrogen content in the sediment, and grain size distribution, depending on degree of vegetation. Eelgrass restoration in Casco Bay will likely be limited by high pore-water sulfide concentrations.
Searle’s Mind: Brains, Subjects, and Systems
Date: 2023-01-01
Creator: Saul Cuevas-Landeros
Access: Open access
- Throughout this project, I ‘step into the Chinese Room’ presented by philosopher John R. Searle and develop the areas where the Chinese Room Argument succeeds. I have aimed to pick out where Searle has succeeded with the Chinese Room Argument and introduce how it fits in with his school of biological naturalism, as it seems that he already had some conception of it when presenting the Argument. From here, I introduce some of the primary arguments against the Chinese Room Argument because they do not fit with Searle’s overarching theme of biological naturalism. Particularly, Searle’s conception of systems and system features is something he endorses for the biological but immediately labels as silly for the Chinese Room. Following the exposition of systems and system features, I expand on how there is a disconnect between Searle’s use of system features and his view of the Chinese Room Argument. What is so special about Searle’s conception of systems and the systems present in the Chinese Room Argument? Searle should claim that the Chinese Room is simply not the kind of thing that can think. Ultimately, Searle’s philosophy of mind leaves us with either a muddled philosophy or an invalid argument in the Chinese Room, but with much to learn and not forget to consider in the philosophy of mind, such as the important role of subjectivity in our conscious life.
Surfing the Kali Yuga: Tracking the Alt-Right on Twitter
Date: 2023-01-01
Creator: Jaida Hodge-Adams
Access: Open access
- The alt-right is a hyper-extreme, decentralized network of far-right pundits and their doggish supporters that exists almost entirely online. Consumed by conspiracy and identity, the myths of bigoted ideologies like racism, antisemitism, and transphobia are taken for granted, and their ideology calls for violent ends by violent means. In the physical world, members of the alt-right often keep their rhetoric to themselves; Online, however, they find solace in a vast, international network of websites and forums that together form one giant echo chamber into which they can dump their darkest thoughts. Though any individual member of the alt-right may operate uniquely within the context of their home country, together they form a collective, international voice whose strongest claims often transcend borders and resist state-level analysis. Unspeakable acts of violence like mass shootings, senseless killings, and acts of terrorism are unpredictable but become significantly more likely when the rhetorical atmosphere breeds hostility. By demonizing minority groups and spreading ideologies of hate, the alt-right makes these acts of violence more likely. On massive platforms like Twitter, the alt-right’s rhetoric can seep into mainstream conversations; their framing of concepts like race, gender, sexuality, and national identity are forced into relevance. Their rhetoric is euphemistic, but their message is clear, and their hate poses a real threat to people’s lives. This honors project explores the ideological and geographic features of the alt-right and their international implications, concluding that the alt-right is a globally interconnected group of actors whose conspiracies motivate lone-wolf terrorists worldwide.
Do Voters Reward Incumbents for Service Provision? Electoral Accountability in South African Elections
Date: 2023-01-01
Creator: Rory Mayne Devlin
Access: Open access
- Democratic theory suggests that voters reward or punish incumbent political parties in elections by evaluating parties’ ability to provide services. But do voters reward incumbent parties for service provision in practice? This project explores the relationship between municipal-level service provision and voting in the South African context. I test whether the local provision of services, such as electricity, piped water, internet, trash collection, and flush toilets, impact the performance of South Africa’s two major political parties, the African National Congress (ANC) and the Democratic Alliance (DA) in municipal and national elections between 2009 and 2021. I observe this relationship in ANC- and DA-controlled municipalities using municipal-level data on public service provision, election results, and nighttime brightness levels. The municipal-level results show that DA-controlled municipalities with higher levels of service provision in 2016 offered more support for the DA in the 2021 and 2019 elections. However, ANC-controlled municipalities with higher levels of 2016 service provision did not support the ANC at higher rates. Additionally, ANC-controlled municipalities that improved service provision between 2011 and 2016 supported the ANC at higher rates in the 2021 and 2019 elections than they did in previous elections. DA vote share did not increase in DA-controlled municipalities where services improved over time.
The Current Support Theorem in Context
Date: 2023-01-01
Creator: Ethan Winters
Access: Open access
- This work builds up the theory surrounding a recent result of Erlandsson, Leininger, and Sadanand: the Current Support Theorem. This theorem states precisely when a hyperbolic cone metric on a surface is determined by the support of its Liouville current. To provide background for this theorem, we will cover hyperbolic geometry and hyperbolic surfaces more generally, cone surfaces, covering spaces of surfaces, the notion of an orbifold, and geodesic currents. A corollary to this theorem found in the original paper is discussed which asserts that a surface with more than $32(g-1)$ cone points must be rigid. We extend this result to the case that there are more than $3(g-1)$ cone points. An infinite family of cone surfaces which are not rigid and which have precisely $3(g-1)$ cone points is also provided, hence demonstrating tightness.