Showing 51 - 100 of 681 Items
The Things We Carried: Effect of Exogenous Government Spending Shocks on Wartime Inflation, Evidence from the U.S. and the World Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2029-06-01
Date: 2024-01-01
Creator: Tingjun Huang
Access: Access restricted to the Bowdoin Community
To hum or not to hum: analyzing and provoking sound production in the American lobster (Homarus americanus)
Date: 2024-01-01
Creator: Renske Kerkhofs
Access: Open access
- American lobsters (Homarus americanus) produce humming sounds by vibrating their carapace. These sounds have a fundamental frequency on the order of 100 Hz, with multiple higher harmonics. Though I found no relationship between lobster carapace length and hum frequency, I observed sounds similarly structured to hums but with frequencies an order of magnitude higher, suggesting that lobsters may use a wider range of sounds than previously thought. Using laser vibrometry, I was able to pick up high frequencies of carapace vibration that were similar to those I observed on sound recordings. Lobsters seem to hum most readily when approached from above, but many studies have found it difficult to reliably find soniferous lobsters. To find a way to reliably evoke sound production in American lobsters without contributing to the sound environment, lobsters were exposed to overhead abstract visual stimuli on a screen, after which their behavioral reactions were recorded, as well as any sound production in response to the stimulus. Lobsters responded to the screen stimulus with the same types of behaviors with which they responded to general overhead physical stimuli. This study demonstrates that American lobsters may produce high-pitched sounds and that abstract visual cues can be used as a silent tool to elicit lobster behaviors, but not sound production.
The Federal Disproportionate Minority Contact Mandate: An Examination of Its Effectiveness in Reducing Racial Disparities in Juvenile Justice
Date: 2014-05-01
Creator: Hanna Leigh Wurgaft
Access: Open access
- This paper challenges the effectiveness of the federal Disproportionate Minority Contact mandate. It first traces the legislative history of the mandate, from the Juvenile Justice and Delinquency Act of 1974, to the establishment of the Disproportionate Minority Confinement mandate of 1988, to the final shift to Disproportionate Minority Contact in 2002. It then describes and analyzes implementation of the mandate in the New England states, showing uneven data collection and limited compliance with the mandate. The next chapter explores factors outside the jurisdiction of the DMC mandate that create and perpetuate racial disparities in juvenile justice, including concentrated poverty, police tactics driven in part by federal initiatives, and school disciplinary policies. Ultimately, this paper reports that racial disparities in arrests of juveniles have increased significantly- not declined- during the life of the mandate. It then discusses the limits of federal legislation in remedying racial disparities in juvenile justice.
What Policies Cannot Express: An Examination of Sri Lanka’s Continuing Inability to Bridge the Sinhala-Tamil Ethnolinguistic Divide through National Policies and Programs
Date: 2018-01-01
Creator: Lillian Eckstein
Access: Open access
Disease on the Half-Shell: Prevalence and impact of the protistan pathogen MSX on oyster population health throughout the Gulf of Maine Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2018-05-01
Creator: Madeline Schuldt
Access: Access restricted to the Bowdoin Community
Attentional Inhibition of a Distractor on Memory Facilitation Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2016-05-01
Creator: Jacob M MacDonald
Access: Access restricted to the Bowdoin Community
The Role of Protein Kinases ROG1 and SRF6 in the WAK Stress Response Pathway
Date: 2015-05-01
Creator: Jaepil E Yoon
Access: Open access
Efficacy of Curcumin as a Neuroprotectant Against Dibutyl Phthalate (DBP) - Induced Effects on the Mammalian Spinal Cord Locomotor Neural Network This record is embargoed.
- Embargo End Date: 2027-05-15
Date: 2024-01-01
Creator: Eliza Schotten
Access: Embargoed
Three-Year-Old Agents of Social Change: How aeioTU Educators Build on Children’s Agency
Date: 2024-01-01
Creator: Andrea Rodriguez
Access: Open access
- aeioTU is a Colombian organization that works to enact social change through the field of early childhood education. In collaboration with the Colombian government, aeioTU oversees several public centers located in socioeconomically vulnerable municipalities in Colombia. This thesis analyzes the aeioTU curriculum and the practices of several aeioTU teachers through the theoretical lens of Freire’s critical pedagogy. This thesis argues that by fostering critical awareness of the world from an early age, as well as by collaborating closely with mothers and the communities at large, aeioTU teachers equip children with the tools to become social agents who can challenge and positively change their lived realities. The research presented in this thesis affirms the potential of aeioTU teachers to enact social change in socioeconomically vulnerable communities by building on young children’s social agency.
Plutonic lithics record dynamics in the magmatic system beneath the Akaroa Volcanic Complex, New Zealand Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2018-05-01
Creator: Elizabeth Teeter
Access: Access restricted to the Bowdoin Community
The Determination of the Aqueous Oxidation Potentials of Aniline and Sixteen of its Derivatives via Ultrafast Cyclic Voltammetry to Model the Photocatalyzed Degradation of Organic Pollutants in Natural Bodies of Water Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2014-05-01
Creator: Joshua V Pondick
Access: Access restricted to the Bowdoin Community
Eelgrass meadow structure drives epifaunal community composition more than temperature during a Marine Heat Wave in the Gulf of Maine This record is embargoed.
- Embargo End Date: 2029-05-16
Date: 2024-01-01
Creator: Nicholas Takaki Tienhui Yoong
Access: Embargoed
Identification of Mutations in WAK Locus in Arabidopsis thaliana Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2017-05-01
Creator: Arman Ashrafi
Access: Access restricted to the Bowdoin Community
The Rising Tide of Indigenous Mobilization: Identity and the Politics of Refusal in Mexico and Ecuador
Date: 2016-05-01
Creator: Kelsey J Freeman
Access: Open access
Evaluation of design parameters for monosaccharide probes used in the metabolic labeling of bacterial glycans Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2024-01-01
Creator: Sophia Elisabeth Nigrovic
Access: Access restricted to the Bowdoin Community
Written in the Body: Embodiments of Gender, Asexuality, Queerness, and Disability Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2023-01-01
Creator: Corey Schmolka
Access: Access restricted to the Bowdoin Community
Changes in chiropteran community structure associated with the white-nose syndrome epidemic: evidence for competitive release? Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2014-05-01
Creator: Adam Eichenwald
Access: Access restricted to the Bowdoin Community
Something’s Gotta Give: Guns, Youth, and Social Change in Denver, Colorado Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2019-05-01
Creator: Carlos Manuel Holguin
Access: Access restricted to the Bowdoin Community
The Voice of "Real America:" Trump, Trumpism, and Rural Voters Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Matthew Russell Duthaler
Access: Access restricted to the Bowdoin Community
The Contemporary Role of International Courts:
Challenges Faced in the Conflict in Gaza Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Mary E. John
Access: Access restricted to the Bowdoin Community
International Courts as Venues for Climate Activists: Conceptualizing the Effectiveness of International Climate Litigation Through Norm Development
Date: 2025-01-01
Creator: Ciara McMillan Tran
Access: Open access
- This thesis explores the emergence of international courts as venues for climate activists, and how climate litigation connects climate change-related damages to human rights law to broaden human rights norms related to the environment. Through three case studies of international climate cases, this project evaluates the effectiveness of international climate litigation through direct effectiveness, indirect effectiveness, and normative effectiveness. It argues that international climate cases are involved in the work of larger transnational advocacy networks who engage with issue framing that presents their causes to both a legal and a public audience. Framing is an ongoing, contested process that both activists and respondent states engage with, but the processes of norm development and socialization it prompts may ultimately work to advance the idea of climate and environment-related rights.
Exploring Auditory Compensatory Neuroplasticity and Negative Phonotactic Behavior in G. bimaculatus Through Computer Vision and Machine Learning-Driven Analysis Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Chongye "Tom" Han
Access: Access restricted to the Bowdoin Community
Introgression and adaptive gene flow in a Tropical Eastern Pacific parrotfish hybrid swarm This record is embargoed.
Date: 2025-01-01
Creator: Jolie R. Ganzell
Access: Permanent restriction
Hybrid Pixel-Superpixel Structures for Enhanced Image Segmentation:
Integrating Boundary Information in Deep Learning Models
Date: 2025-01-01
Creator: Jack Roberts
Access: Open access
- This project explores novel approaches to image segmentation using U-Net, leveraging superpixels to enhance accuracy. The first part investigates augmenting standard image inputs by encoding and integrating superpixel information, including an extension that reintroduces this information throughout the encoder. While results show that these methods can offer consistent improvements over the baseline, the gains are modest and suggest room for further optimization. The second part introduces a hybrid data structure, the Superpixel-Integrated Grid (SIGrid), which embeds superpixel boundary, shape, and color descriptors into a regular n × n grid. SIGrid enables more efficient training on smaller architectures while achieving noticeably higher segmentation accuracy, highlighting its potential as a lightweight and effective input representation. The code developed for this project can be found at: https://github.com/JackRobs25/Honors
Where Have All the Black Americans Gone? -- Black Americans, Black Immigrants, and Descendants of Immigrants at Elite, Private Colleges Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Gabrielle Nicole Waller-Whelan
Access: Access restricted to the Bowdoin Community
Time series of carbonate chemistry parameters, process investigation, and parameter modeling in the Basin Preserve, the New Meadows River, and Harpswell Sound, Maine Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Eli G. Franklin
Access: Access restricted to the Bowdoin Community
Forest regeneration and understory plant communities after introduced herbivore eradication on a boreal island Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Mitchell F. Zell
Access: Access restricted to the Bowdoin Community
The modulation of calcium-activated potassium channels for the stabilization of mammalian spinal locomotor activity This record is embargoed.
- Embargo End Date: 2026-12-14
Date: 2023-01-01
Creator: Hattie Sargent Slayton
Access: Embargoed
A Suite of Tools for Analyzing Hydrology and Geomorphology in Impounded Rivers
Date: 2025-01-01
Creator: Benjamin Wong Halperin
Access: Open access
- Large impoundment dams have well-documented impacts on hydrologic and geomorphicfunction. Numerous tools and metrics have been developed over time to characterize theseimpacts, but they remain disparate, are often applied in a small number of studies, and rarelyapplied in concert with each other. Utilizing the open-source programming language R, Iassemble a suite of metrics known as DAMS – the Dam Analysis and Metrics Suite – thatcombines several pre-existing metrics for characterizing dam impacts into one script. Thesemetrics include the Indicators of Hydrologic Alteration to characterize hydrologic change; themean streambed elevation to characterize vertical change in the river; and sediment mass balanceand flood magnitude reduction. By combining these schemas, DAMS provides a flexible andcomprehensive way to characterize the impact of dams on hydrology and geomorphology.I apply DAMS to two dams in diverse geographic settings: the Buford Dam on theChattahoochee River in Georgia and the Harris Station Dam on the Kennebec River in Maine.Both are hydroelectric dams with long stream gage records before and after dam construction. Ifound that the Buford Dam has caused a decrease in high flows in the Chattahoochee River aswell as a change in the seasonality of flows. I found that the Kennebec River has seen anincrease in high and peak flow volume after the construction of the Harris Station Dam, but thisincrease is less than comparable unimpounded rivers. The geomorphic data the ChattahoocheeRiver is fairly limited and cannot be access for the Kennebec River at all, meaning that DAMSwas unable to tell a complete story about how these rivers changed due to impoundment,highlighting the need for increased monitoring on all of the United States’ rivers.
How the Caregiver Learns to Care: Institutional, Resource, and Emotional Tensions Among Sexual Assault Support Staff
Date: 2025-01-01
Creator: Hanna Cha
Access: Open access
- This study examines the institutional and emotional dynamics within a multidisciplinary team that consists of law enforcement (LE), the Department of Health and Human Services (DHHS), and sexual assault support staff who handle child sexual abuse cases. Employees interpret trauma differently depending on the organizational framework they operate within. The way professionals construct trauma shapes caregivers’ outlook on the process and ultimately affects how they care for their children. While LE and DHHS prioritize legal compliance, the sexual assault support staff advocate for trauma-informed care. Using semi-structured interviews with seven sexual assault support staff members who identified as women or non-binary, this research explores the way they manage the gendered burden of emotional labor, the systemic undervaluation of trauma-informed practices, and the emotional challenges caregivers face in supporting child survivors. Findings show the friction between the multidisciplinary team, emphasizing the need for integrated trauma-informed training and community-based support systems for caregivers.
Quantification and Characterization of AST-C Peptides in Homarus americanus Using Mass Spectrometry
Date: 2014-08-01
Creator: Amanda Howard
Access: Open access
- Neuropeptides are small signaling molecules found throughout the nervous system that are responsible for influencing animal behavior. They consist of short amino acid chains and interact with cell-membrane receptors in order to regulate behavioral responses (Fig. 1a). The American lobster, Homarus americanus, has proven to be a strong model organism in which to study such activity due to the simplicity of the system and the wealth of existing knowledge about the animal. One neuropeptide found in H. americanus is a C-type allatostatin (AST-C). Allatostatins are a family of neuropeptides originally identified in insects that inhibits juvenile hormone production. The H. americanus AST-C has a pyroglutamate blocked N-terminus and an unmodified C-terminus (Fig. 1b). In addition to AST-C, a different, yet structurally similar neuropeptide has been found in H. americanus. This peptide has an unmodified N-terminus and an amidated C-terminus (Fig. 1c). Both forms of AST-C (referred to as ASTC-real and ASTC-like) also have a disulfide bond between their two cysteine residues. In the lobster, both peptides influence cardiac muscle contraction patterns and have been found in various tissues throughout the nervous system [1, 2]. In order to establish the purpose of the observed post-translational modifications, this study aims to find whether these peptides exist in other forms in the lobster and to determine their relative and absolute concentrations.Liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (MS/MS) are often used in analytical chemistry to characterize complex samples and identify neuropeptides. First, sample components are separated by chromatography based on properties such as size and hydrophobicity. Using mass spectrometry (MS), peptides are protonated (positively charged) and their mass is determined from their measured mass-to-charge ratios. These peptides are lastly fragmented into many ions using MS/MS, which ultimately allows them to be sequenced in order to determine their identity. This summer, standards of the two AST-C peptides have been characterized by LC-MS/MS. The reduced forms of both peptides have been synthesized by chemically reducing the disulfide bond and were also analyzed by MS/MS. As expected, the structural stability provided by the disulfide bond prevented fragmentation during MS/MS analysis; that is, there was evidence of more fragmentation in the reduced forms than in the fully processed forms (Fig. 2). When looking for other forms of ASTC, these findings will facilitate the identification of the reduced forms in crustacean tissue.To assess the accuracy of the detection method used, detection limits were assessed by analyzing sample matrices augmented with known amounts of peptide standards. The smallest amount of peptide detected from a single injection was 25 fmol (2.5·10-14 mol) peptide. There appeared to be a strongly linear relationship between the amount of ASTC-real injected and the instrument response (chromatographic peak area) (R2=0.996, n=6). However, the relationship between the amount of ASTC-like injected and the instrument response was less linear (R2=0.802, n=5), and the calibration slope was more shallow, indicating that this peptide is more difficult to detect. This is possibly because ASTC-real, unlike ASTC-like, contains an arginine (R) and a histidine (H) residue, two basic amino acids susceptible to protonation. Therefore, it seems that ASTC-real is more easily protonated during the ionization process in MS analysis, causing it to be more readily detected.Lastly, ASTC-real has been identified in the pericardial organ (PO), a tissue responsible for delivering neuropeptides manufactured in the thoracic ganglion to the heart in order to control muscle contraction. ASTC-like is also believed to be present in the PO based on previous work in the Dickinson lab (E. Dickinson, unpublished data), but it is likely that it has not yet been detected in this study due to the detection limitations described above. To address these issues, more tissues will be pooled to increase the amount of peptide in each sample analyzed.Currently, tissue extraction methods are being optimized to eliminate phospholipid contamination and to maximize detection sensitivity. Specifically, two separate extraction solvents as well as a chloroform delipidation procedure are being tested. Future goals include quantifying peptide levels by adding a known amount of internal standard to the samples and comparing instrument responses for ASTC and for internal standard. Additionally, known amounts of peptide standard will be brought through the extraction process to determine the amount of peptide loss throughout this procedure. During the upcoming academic year, this study will be continued as an Honor’s project. Further research in these areas will ultimately help explain how neuropeptides interact to regulate behavior within the lobster and in more complex systems. Final Report of research funded by the Henry L. and Grace Doherty Charitable Foundation Coastal Studies Research Fellowship.
Effects of octopamine and tyramine on the cardiac system of the lobster, Homarus americanus
Date: 2019-05-01
Creator: Casey Breslow
Access: Open access
- Modulation in neural systems is important for regulating physiology and behavior (Wright et al., 2010). Peptides, hormones, and amines are common neural modulators, acting on many neural systems across species. One group of neural networks that can be regulated are central pattern generators (CPGs), which generate rhythmic neural patterns, which drive behaviors (Marder and Bucher, 2001). Octopamine, and its precursor tyramine, are two amines that have been found to regulate (CPGs) across species (Cooke, 2002; Fussnecker et al., 2006). One role of octopamine in the decapod neurogenic heart is regulating the frequency and the duration of heart beats. However, the precise site of octopamine modulation within the cardiac system is not yet known (Kurumoto and Ebara, 1991). One possible site of action is the cardiac ganglion (CG), the CPG in decapod hearts. The transcripts for the enzymes required to synthesize octopamine from tyramine have been identified and localized in the CG (Christie et al., 2018). This would suggest that octopamine is produced in the CG, where it could have a direct action on those neurons, or it could be released peripherally. We have found individual variation in the response to octopamine and its precursor tyramine, and significant effects of frequency and contraction amplitude in the whole heart.
Midterm Decline in Comparative Perspective
Date: 2019-05-01
Creator: Duncan Gans
Access: Open access
Beyond Urban Bias: Peasant Movements and the State in Africa
Date: 2019-05-01
Creator: Connor Rockett
Access: Open access
- Focusing on sub-Saharan Africa, this study tests the hypothesis that state intervention in agrarian economies causes peasant movements to engage in broad-based contention, on regional and national levels. The study traces the connections between government land and agricultural institutions and the characteristics of rural movements that make claims on them. Case studies of regions of Tanzania, Senegal, Côte d’Ivoire, and Ethiopia show the ways in which rural movements are constructed in response to the political and social environments in which they arise. That is, the comparisons demonstrate that the character of political authority and social organization are important determinants of the form taken by peasant movements.
Ecological Effects of Rockweed (Ascophyllum nodosum) Harvesting
Date: 2014-08-01
Creator: Christine Walder
Access: Open access
- Ascophyllum nodosum, the dominant intertidal macroalgal species from Maine to Canada, plays an important role in buffering intertidal stresses and supports a variety of organisms such as molluscs, crustaceans, fish and birds. A. nodosum is harvested commercially for use in fertilizers and food additives, and landings have been increasing in Maine in recent years. The ecological impact of removing the rockweed canopy was assessed in a comparative study between Kent Island in the Bay of Fundy, New Brunswick, Canada and Orr’s Island in Harpswell, ME, USA. Paired 2x2m control and experimental plots were set up, harvested, and surveyed monthly during the summers of 2013 (15 plots on Kent Island) and 2014 (an additional 9 plots on Kent Island and 20 on Orr’s Island) in a BACI design (Before, After, Control, Impact). One square meter surveys were conducted to determine algal species richness, algal percent secondary cover, and megafauna abundance and diversity. Surveys were designed to assess the overall diversity within plots and count/identify all present species. Initial t-tests of Kent Island data show a short-term reduction in amphipods and isopods, Carcinus maenas (green crabs), and Littorina obtusata (smooth periwinkles) and a short-term increase in Littorina littorea (common periwinkles) (p Final Report of research funded by the Rusack Coastal Studies Fellowship (2014).
Tension production and sarcomere length in lobster (Homarus americanus) cardiac muscles: the mechanisms underlying mechanical anisotropy Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2019-05-01
Creator: Matthew Maguire
Access: Access restricted to the Bowdoin Community
The evolutionary response of populations of the blue mussel (Mytilus edulis) populations to climate change
Date: 2014-08-01
Creator: Jenna Watling
Access: Open access
- Since early July, I’ve been working on three projects. I’ve been studying parrotfish speciation, dissecting green crabs, and collecting samples of muscle tissue from blue mussels. My primary occupation is the study of parrotfish speciation with Dr. Carlon. He has found evidence of speciation through hybridization, which is has not been commonly observed. During the 2013-2014 academic year, he and I extracted DNA from fin or scale samples from Pacific parrotfish. Throughout the year and during this summer, we have been amplifying specific genes—nuclear and mitochondrial—using a polymerase chain reaction, confirming the amplification via gel electrophoresis, and preparing the samples for Sanger sequencing, which is done by the Nevada Genomics Center. Once we receive the sequencing results electronically, I use the program Geneious to check the quality of the individual sequences and resolve ambiguous calls (e.g., whether a specific base pair is an arginine or a cytosine) and align the sequences so we can compare them base pair by base pair. By examining both nuclear and mitochondrial genes, which evolve at different rates, we can hypothesize about the way in which different species arise. Green crab (Carcinus maenas) dissection is an early step in Aidan Short’s analysis of their diet. I assist in collecting tissue samples. We collect muscle tissue from the crabs’ claws. These samples will allow Aiden to differentiate between the crabs’ food and the crabs themselves. Then their carapaces are cut open and their entire stomachs are collected. In the near future, Aidan will use next-generation sequencing to identify any species present in the crab stomachs and quantify the abundance of these species’ DNA. Sequencing the crabs’ stomach contents is more precise and more complete than the older method of hard part analysis. The green crabs’ diet is of interest because green crabs are an invasive species and have been implicated in loss of sea grass beds and decreasing soft shell clam populations. Collection of tissue from blue mussels (Mytilus edulis) and bay mussels (M. trossulus) is a preliminary step for Dr. Sarah Kingston’s investigation of the genetic basis of variation in shell calcification rate under environmental conditions possible due to ocean acidification. She collects mussels from various sites along the Maine coast, marks each with a color and number, and records their buoyant weight. The buoyant weight allows Dr. Kingston to determine the mass of the shells without having to kill the mussels. In the first round of experiments, Dr. Kingston determined which of three experimental schemes (involving the manipulation of food levels, temperature, and pH) resulted in the greatest variation of shell calcification after two weeks. The harshest scheme—no food, high temperature, and low pH—resulted in the greatest variation, and this scheme will be used in the experiment going forward. After the experimental period, the mussels are re-weighed and tissue samples are collected. I assist in tissue sample collection; we cut open the mussels and remove the foot and the adductor muscle. In the next round of experiments, I will further assist by participating in mussel collection, monitoring tank conditions during the experimental period, and labeling and weighing the specimens. The DNA libraries obtained from the tissue samples will be sent away for next generation sequencing, and Dr. Kingston will begin looking for genetic variation associated with calcification rates. Final Report, summer 2014 student-faculty research.
Active and Passive Spatial Learning and Memory in Human Navigation
Date: 2019-01-01
Creator: Caroline Rice
Access: Open access
- Previous studies show that active exploration of an environment contributes to spatial learning more than passive visual exposure (Chrastil & Warren, 2013; Chrastil & Warren, 2015). Active navigation and cognitive decision-making in a novel environment leads to increased spatial knowledge and memory of location compared to a passive exploration that removes the decision-making component. There is evidence of theta oscillations present in electroencephalography (EEG) recordings from the hippocampus and pre-frontal cortex (PFC). These low-frequency waves could reflect spatial navigation and memory performance, suggested by their involvement in communication between the formerly named brain regions. Through communication with the hippocampus, theta oscillations could be involved in the integration of new spatial information into memory. While undergoing EEG, subjects in this study either actively or passively explored a virtual maze, identified as the “Free” or “Guided” groups, respectively. After exploring, subjects’ spatial memory of the maze was tested through a task that required navigation from a starting object to a target object. Behavioral data show increased spatial memory for the Free group, indicated by significantly greater navigation to the correct target object in the memory task. EEG results indicate significantly greater theta oscillations in frontal regions for the Free group during the exploration phase. These results support those found in previous studies and could indicate a correlation between frontal theta oscillations during learning of novel environments and spatial memory.
An Assessment of pH and the Effects of Ocean Acidification in a Phippsburg, ME Clam Flat
Date: 2014-08-01
Creator: Lloyd Anderson
Access: Open access
- Increased atmospheric CO2 due to the combustion of fossil fuels and subsequent oceanic uptake has led to a phenomenon known as ocean acidification: CO2 gas dissolved in the ocean lowers surface ocean pH and acidifies ocean waters, a process which has raised global concern. The purpose of my research was to investigate why a particular clam flat in Phippsburg, ME is not as productive as it used to be. This clam flat, located on “The Branch” in Phippsburg adjacent to Head Beach, has decreased to approximately a sixth of its former productivity in just over a decade. A possible explanation for this drop in clam bed productivity is acidification. I worked in a partnership with Bailey Moritz ’16, with the goal to measure indicators of ocean acidification in the clam flat and see if there was a difference in those indicators between productive and unproductive areas of the flat. Bailey’s focus was alkalinity, a quantification of the buffering capacity of seawater, where my specific research focus was on the effective collection of pH measurements. We were ultimately able to combine our alkalinity and pH measurements to calculate saturation state, an indicator of the susceptibility of clam shells to dissolution. I measured pH, a direct indicator of water acidity, from the top centimeter of the mudflat, the region where clam spat (juvenile clams) are seeded. The first few weeks of my fellowship time I spent researching the most accurate and precise way to measure pH in the field, and ultimately decided to measure pH on site using glass electrode probes. Sites 1 and 2 were located in a productive region of the flat, sites 4 and 5 were located in an unproductive region, and site 3 was located on the boundary between the two zones. Average pH values within the clam flat ranged from 6.9-7.5, and there was no significant difference in pH between productive and unproductive sites across the flat (Figure 1). The wide variations in pH across this clam flat could potentially be attributed to daily shifts in temperature, freshwater input, and biological productivity in the sediments. Low average pH values seen across all sites contribute to a low saturation state across the flat: our average calculated saturation state was 0.47, lower than similar data measured by Green et al. on a clam flat in South Portland in 2013, where average saturation state was 0.9. Our data indicate that the soft-shell clams at the productive sites in this particular Phippsburg clam flat are managing to survive in undersaturated (saturation state < 1) conditions. Since saturation state was low across both productive and unproductive sites, ocean acidification seems not to be the cause for the clams’ decline. However, other factors such as dissolved oxygen or sediment type may have combined with low saturation states to create a difference in productivity across the flat. In further research I would be interested to see how average pH at these same sites varies over a year-long period, which would give a better representation of the environment that the soft-shell clams are exposed to through yearly cycles. Final Report of research funded by the Rusack Coastal Studies Fellowship.
GIS analysis of historical cod fisheries in the Gulf of Maine
Date: 2014-08-01
Creator: Nora Hefner
Access: Open access
- Gulf of Maine cod fisheries, once essential to Maine’s economy and culture, are currently in a state of collapse. Following a long decline throughout the 1800s and two collapses in the 1900s – one in the middle of the century and one in the 1990s, cod populations along the coast exist now as small fractions of their former bounty. Though the connection was largely forgotten in the twentieth century, fishermen in the nineteenth century attributed the decline of the cod fishery to the loss of alewives, an anadromous river herring upon which cod prey. Alewives have been cut off from their spawning and nursery habitat along much of the Gulf of Maine due to the damming of rivers that empty into the Gulf. My research is a part of an ongoing study that aims to establish the historical relationship between cod and other gadoid groundfish fisheries, their ecosystems, and anadromous alewives using spatial data from geographic information systems (GIS). GIS maps were created with the positions of 466 historical Gulf of Maine cod fishing grounds, identified using a database developed by fisheries scientist Ted Ames (whose work is largely responsible for fisheries scientists’ renewed interest in the groundfish-alewife connection). The spatial database generated from these data will be analyzed using a logistical regression to identify characteristics of fishing grounds that define them as fishing grounds, as well as characteristics that determine the relative quality of individual fishing grounds. The Ames database contains data in two main categories: biophysical (ecosystem characteristics) and socioeconomic (infrastructure). The focus of my research was on generating two specific data sets from historical literature, government reports, and experts in the field, and on mapping that data using GIS software (see Figure 1). The first was a list of rivers that supported annual alewife runs before the mid-twentieth century cod groundfish fishery collapse. Using GIS software, I mapped the locations at which these rivers enter the ocean, creating spatial data that show the point at which cod in the Gulf and alewives in the rivers would meet. The second data set was a list of ports and harbors that supported the groundfish industry, also before the mid-twentieth century collapse. These locations were mapped as the areas from which fishing boats would set out in pursuit of groundfish, again creating a set of spatial data points. Both of these data sets were added to the existing spatial database. My data and Ames’ data will be used to calculate distances between individual groundfish fishing grounds and historic alewife runs and between fishing grounds and ports and harbors. Statistical analyses will determine both whether those two factors have any significant relationship with fishing ground quality and the nature of their effects, if any. Ultimately, the results of these analyses will contribute to an increasingly detailed picture of the Gulf of Maine as it existed – physically, ecologically, and economically – when it still supported astoundingly large populations of cod and other groundfish. With a better idea of what the system looked like when it worked properly, we can make a more informed and focused attempt to rebuild it. This research provided me with opportunities to develop practical skills like use of GIS software, contacting and collaborating with scientists, researchers, and government agencies in my field, and data management. I also gained a greater understanding of and appreciation for the complexity and challenge of trying to bring research from the science level to management policy and action. Final Report of research funded by the Cooke Environmental Research Fellowship
Pyrokinin peptides’ effect on the stomatogastric nervous system in the American lobster, Homarus americanus
Date: 2014-08-01
Creator: Xuan Qu
Access: Open access
- Central pattern generators are networks of neurons that produce rhythmic and repetitiveoutputs. These outputs control behaviors such as walking, breathing and digestion. In the Americanlobster, central pattern generators control the behavior of muscles in its foregut, which allows thedigestion of a variety of food types. The stomatogastric ganglion (STG) is a bundle of about thirtyneurons in the foregut of American lobsters. It has been studied extensively since each one of theneurons in it is both identifiable and produces simple patterned outputs. The analysis of American lobster’s stomach behaviors and the neural mechanisms controlling them could provide general insights into how rhythmic motor patterns for locomotion are produced. A large number of the neurons in the STG are modulatory neurons that use neuromodulators for at least part of their synaptic receptions. These neuromodulators are released by neurons and cause long-lasting changes in the synaptic efficacies of the targets. At present, many types of neuropeptides have been identified within the crustacean stomatogastric nervous system. The pyrokinins are members of one peptide family, PBAN. PBAN peptides all share the common Cterminalpentapeptide FXPRL-amide, in which X can be S, T, G, N, or V. Previous studies, using immunohistochemistry, have found that there are pyrokinin peptides present in both the STG and the cardiac ganglion (CG) of American lobsters. My research tests five different kinds of pyrokinin peptides, including PevPK1 (DFAFSPRLamide) and PevPK2 (ADFAFNPRLamide) from the shrimp L.vannamei (Torfs et al., 2001; Ma et al., 2010), CabPK1 (TNFAFSPRLamide) and CabPK2(SGGFAFSPRLamide from the crab C.borealis (Saideman et al., 2007;Ma et al., 2009) and Conserved Sequence (FSPRLamide) from the lobster, H.americanus (Ma, et al, 2008). ConservedSequence, the only pyrokinin identified in the American lobster so far, is highly conserved among many other pyrokinin peptides. Therefore, it is believed to be just a fragment with the complete sequence yet to be identified. Thus, we predicted that it might produce a weaker effect on the STG. Previous studies on the pyrokinin peptides have shown that in crabs, CabPK1, CabPK2 and LeucoPK (identified in an insect), all had a virtually identical effect on the CG, suggesting that the differences among these pyrokinin peptides are not important and the receptors for these peptides are the same. However, research done by Bowdoin students in 2011-2012 showed that among PevPK1,PevPK2, CabPK1, CabPK2, and Conserved Sequence, all but Conserved Sequence (not yet tested) had strong effects on the STG. However, only PevPK2 had an effect on the CG. My goal for this summer research was to determine whether or not there are differences between the responses of the STG to the different peptides in order to further determine the cause for the differences between the responses of the CG and those of the STG. The results from the extracellular recordings from the identified neurons in my research have shown that none of the five kinds of pyrokinin peptides affect the pyloric rhythm, which controls the pumping and filtering of food through the pylorus in Americanlobsters. They all, however, excite the gastric mill rhythm, which controls the movements of the teeth that grind up the food before it is transferred into the pylorus. Moreover, there is no significant difference among the effects of these five kinds of pyrokinin peptides. Conserved Sequence, which was predicted to produce a relatively weaker effect, proved to produce virtually identical effect asfour other kinds of pyrokinin peptides. Future research will focus on studying the differences between the STG and CG to determine the cause of the varied responses between them. Final Report of research funded by the Doherty Coastal Studies Research Fellowship.
Traders and Troublemakers: Sovereignty in Southern Morocco at the End of the 19th Century
Date: 2020-01-01
Creator: Joseph Campbell Hilleary
Access: Open access
- This thesis explores changes in and challenges to Moroccan political authority in the region of the Sous during the late nineteenth century. It attempts to show how the phenomenon of British informal empire created a crisis over Moroccan sovereignty that caused the sultan to both materially and discursively change the way he wielded power in southern Morocco. It further connects these changes and the narrative contestation that accompanied them to the construction of the Bilad al-Siba/Bilad al-Makhzan dichotomy found in Western academic literature on Morocco starting in the colonial period. It begins with an examination of letters between Sultan Hassan I and local leaders in the Sous that show a shift toward a more bureaucratic form of governance in response to repeated openings of black-market ports by British trading companies. It then investigates the textual debate over the framing of Hassan I’s military expeditions to southern Morocco in the 1880s and 90s by drawing on a collection of European travel accounts, American consular reports, and a royal Moroccan history. Finally, it ties the illegal trade in the Sous to the broader theory of informal empire through a close examination of the Tourmaline Incident of 1897, using documents from the British Foreign Office as well as published accounts by crew members aboard the Tourmaline, itself.
Photosynthetic phenology of a boreal spruce forest observed at stand and needle scales This record is embargoed.
- Embargo End Date: 2025-05-19
Date: 2022-01-01
Creator: Jeremy A. Hoyne Grosvenor
Access: Embargoed
Finite Element Modeling of Piezoelectric Surface Wave Focusing Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2022-01-01
Creator: Kieran Enzian
Access: Access restricted to the Bowdoin Community
A Problem Best Put Off Until Tomorrow
Date: 2023-01-01
Creator: Evan Albers
Access: Open access
- Effective Altruism has led a recent renaissance for utilitarian theory. However, it seems that despite its surge in popularity, Effective Altruism is still vulnerable to many of the critiques that plague utilitarianism. The most significant amongst these is the utility monster. I use Longtermsim, a mode of thinking that has evolved from Effective Altruism and prioritizes the far-future over the present in decision-making processes, as an example of how the unborn millions of the future might constitute a utility monster as a corporate mass. I investigate three main avenues of resolving the utility monster objection to Effective Altruism: reconsidering the use of expected value, adopting temporal discounting, and adopting average utilitarianism. I demonstrate that at best there are significant problems with these responses, and at worst, they completely fail to resolve the utility monster objection. I then conclude that if situations do exist in which the costs to the present do not intuitively justify the benefits to the far future, we must reject utilitarianism altogether.
Design, Fabrication, and Characterization of Unidirectional Interdigital Transducers Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2022-01-01
Creator: Shane Anthony Smolenski
Access: Access restricted to the Bowdoin Community
The Regulatory Effect of High Dopamine on the Hyperpolarization-Activated Inward Current (Ih) and its Role in the Stability and Rhythmicity of Mammalian Locomotor Neural Networks Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2022-01-01
Creator: Abigail Raymond
Access: Access restricted to the Bowdoin Community
Exploiting Context in Linear Influence Games: Improved Algorithms for Model Selection and Performance Evaluation
Date: 2022-01-01
Creator: Daniel Little
Access: Open access
- In the recent past, extensive experimental works have been performed to predict joint voting outcomes in Congress based on a game-theoretic model of voting behavior known as Linear Influence Games. In this thesis, we improve the model selection and evaluation procedure of these past experiments. First, we implement two methods, Nested Cross-Validation with Tuning (Nested CVT) and Bootstrap Bias Corrected Cross-Validation (BBC-CV), to perform model selection and evaluation with less bias than previous methods. While Nested CVT is a commonly used method, it requires learning a large number of models; BBC-CV is a more recent method boasting less computational cost. Using Nested CVT and BBC-CV we perform not only model selection but also model evaluation, whereas the past work was focused on model selection alone. Second, previously models were hand picked based on performance measures gathered from CVT, but both Nested CVT and BBC-CV necessitate an automated model selection procedure. We implement such a procedure and compare its selections to what we otherwise would have hand picked. Additionally, we use sponsorship and cosponsorship data to improve the method for estimating unknown polarity values of bills. Previously, only subject code data was used. This estimation must be done when making voting outcome predictions for a new bill as well as measuring validation or testing errors. We compare and contrast several new methods for estimating unknown bill polarities.
Investigating the role of eyes absent in photoreceptor axon targeting in Drosophila melanogaster
Date: 2021-01-01
Creator: Bethany J. Thach
Access: Open access
- The eya gene is essential to development of the Drosophila visual system and eye-specific loss of function mutations in the gene commonly result in the missing eye phenotype. The eya2m35g mutation carries a deletion of exon 1B and adjacent regulatory sequences. Flies carrying the eya2m35g allele exhibit a photoreceptor axon phenotype that has not previously been associated with the eya gene. To determine a potential role for eya in photoreceptor axon targeting, I characterized various phenotypes of eya2m35g mutants and generated additional eya alleles consisting of smaller deletions within the eya2m35g mutation to locate the genetic source of axonal disruption. Using immunofluorescence staining to visualize Eya protein, I found a loss of eya expression in the optic lobe region of eya2m35g stage 9 embryos and third instar larvae. I also observed a loss of retinal basal glial (RBG) cells in the larval eye disc. Finally, I demonstrated that the disconnected axon phenotype is generated when a region of the intron immediately downstream of exon 1B is deleted. These findings suggest that a possible regulatory element for eya that is essential for photoreceptor axon targeting exists in this intronic region.