Showing 451 - 500 of 681 Items
Effects of Picrotoxin Application on the Cardiac Ganglion of the American Lobster, Homarus americanus
Date: 2023-01-01
Creator: John T Woolley
Access: Open access
- Picrotoxin (PTX) has been employed extensively as a tool within the crustacean stomatogastric nervous system (STNS) for its efficacy in blocking K+ and Cl+ currents gated by both GABA and glutamate. Through blocking some currents in the STNS, PTX allows for examination of other components without their presence. However, effects of PTX are relatively unknown within the lobster’s cardiac ganglion (CG). As an incredibly small nervous system of only nine neurons, the lobster CG presents an excellent model system for studying neural circuits. Given that the chemical synapses in the CG are mediated by glutamate, the present study aimed to investigate the action of PTX in the lobster CG with the intent of better understanding its pharmacological impacts as a potential tool for studying the system. Therefore, this study aimed to establish the effects of PTX on CG responses to the application of exogenous GABA or glutamate. When data from both modulators were pooled, PTX applied at a concentration of 10-5M had significant effects on burst duration but not duty cycle or burst frequency of the CG. PTX did suppress GABA (5x10-5M) mediated inhibition of burst duration and duty cycle. PTX did not have any significant effects on burst duration, duty cycle, or frequency compared to exogenous glutamate application. These results indicate that glutamatergic inhibitory synapses are not present in the CG and PTX partially suppresses only GABAergic responses in this system.
Effects of myosuppressin, a peptide neuromodulator, on membrane currents in the crustacean cardiac ganglion
Date: 2022-01-01
Creator: Anthony Yanez
Access: Open access
- Central pattern generators are neural circuits that can independently produce rhythmic patterns of electrical activity without central or periphery inputs. They control rhythmic behaviors like breathing in humans and cardiac activity in crustaceans. Rhythmic behaviors must be flexible to respond appropriately to a changing environment; this flexibility is achieved through the action of neuromodulators. The cardiac ganglion of Homarus americanus, the American lobster, is a central pattern generator made up of four premotor neurons and five motor neurons. Membrane currents in each cell type, which can be targeted for modulation by various molecules, generate rhythmic bursts of action potentials. Myosuppressin, a FMRFamide-like peptide, is one such neuromodulator. The currents targeted for neuromodulation by myosuppressin are unknown. I investigated the molecular and physiological underpinnings of the modulatory effect of myosuppressin on motor neurons in the cardiac ganglion. First, using single cell RT-qPCR, I determined that across animals, motor neurons express myosuppressin receptor subtype II at equal levels relative to each other. Using sharp intracellular recordings, I showed that myosuppressin decreased burst frequency and the rate of depolarization during the inter-burst interval. I predicted that this effect resulted from the modulation of either A-type potassium current or calcium-dependent potassium current. Using two-electrode voltage clamp, I found that total outward current did not substantially change after treatment with myosuppressin. This result was surprising and provides grounds for explorations of subtle forms of neuromodulation in simple neural circuits.
Genetic Analysis of Adhesion Protein ELMO3 in Arabidopsis thaliana
Date: 2022-01-01
Creator: Garrison Asper
Access: Open access
- The Extracellular Matrix (ECM) between plant cells is vital for structure, development, and intercellular adhesion. A pectin rich layer in between cells, the middle lamella, is largely responsible for regulating the adhesive properties of adjacent plant cells. Homogalacturonan (HG) pectin, the most common, is synthesized in the Golgi and secreted into the ECM where it undergoes calcium crosslinking, increasing its adhesive properties. Mutations in proteins essential for HG synthesis can reveal a severe adhesion defective phenotype, where the hypocotyls of dark grown Arabidopsis exhibit cell sloughing, curling, and general disorganization. A family of five ELMO proteins are suspected to act as scaffolds for pectin biosynthesis enzymes. ELMO1 and ELMO4 mutants exhibit an adhesion deficient phenotype, and a double mutant provides evidence of redundancy in function between ELMO1 and ELMO2. ELMO1-GFP co-immunoprecipitated with enzymes required for HG synthesis indicating its role as a scaffold protein. Double mutants of the other ELMO homologues were created to determine if they exhibit functional redundancy, and ELMO1 and ELMO3 appear partially redundant. A gene deletion of ELMO3 was also created using the CRSPR/Cas9 system, resulting in two distinct elmo3 deletion alleles, which were phenotypically identical to the original elmo3-/- mutant. All adhesion defective phenotypes can be partially suppressed by altering the osmoticum and hence turgor that provides pressure on adhesive cells. Lastly, ELMO3-GFP was localized to the Golgi, the site of pectin biosynthesis, further supporting a common role of the ELMOs in pectin biosynthesis.
Reactions Responsible for Aging in Wood-Based Pyrolysis Oil: Synthesis and Characterization of a Coniferyl Alcohol Dimer
Date: 2021-01-01
Creator: Alejandro Garcia
Access: Open access
- The negative environmental impact and the diminishing supply of fossil fuels demand a renewable alternative. Pyrolysis oils produced from the decomposition of biomass, like wood, are a potential fuel substitute for energy production and a feedstock alternative for manufacturing value-added chemicals. The possibilities offered by pyrolysis oils are offset by oil instability. The oils contain reactive compounds, such as small aldehydes, conjugated aromatics, and acids that over time react and produce higher molecular mass products. This instability manifests as an increase in viscosity by a process referred to as aging. One chemical component, coniferyl alcohol, is proposed to react with formaldehyde under the acidic oil conditions to produce a dimer. In our lab, researchers have detected the coniferyl alcohol dimer in authentic oil samples and have simulated the reaction under conditions that removes the complexity of the pyrolysis oil matrix. This study focused on the synthesis, isolation, and characterization of the dimer structure by employing NMR analysis. GC/MS analysis of a successful synthesis of the dimer showed multiple dimers were produced, but there was one principal product. The NMR analysis of this dimer was used to elucidate the geometry, providing evidence that the product has E stereochemistry for the double bond and trans stereochemistry in the acetal ring. Confirmation of the principal structure provides support for the dimerization mechanism and will allow for future research to address instability of pyrolysis oils.
Modeling Coupled Disease-Behavior Dynamics of SARS-CoV-2 Using Influence Networks
Date: 2021-01-01
Creator: Juliana C. Taube
Access: Open access
- SARS-CoV-2, the virus that causes COVID-19, has caused significant human morbidity and mortality since its emergence in late 2019. Not only have over three million people died, but humans have been forced to change their behavior in a variety of ways, including limiting their contacts, social distancing, and wearing masks. Early infectious disease models, like the classical SIR model by Kermack and McKendrick, do not account for differing contact structures and behavior. More recent work has demonstrated that contact structures and behavior can considerably impact disease dynamics. We construct a coupled disease-behavior dynamical model for SARS-CoV-2 by incorporating heterogeneous contact structures and decisions about masking. We use a contact network with household, work, and friend interactions to capture the variation in contact patterns. We allow decisions about masking to occur at a different time scale from disease spread which dramatically changes the masking dynamics. Drawing from the field of game theory, we construct an individual decision-making process that relies on perceived risk of infection, social influence, and individual resistance to masking. Through simulation, we find that social influence prevents masking, while perceived risk largely drives individuals to mask. Underlying contact structure also affects the number of people who mask. This model serves as a starting point for future work which could explore the relative importance of social influence and perceived risk in human decision-making.
The Congressional Database: Designing a Web Application Using an HCI Approach
Date: 2021-01-01
Creator: Liam R. Juskevice
Access: Open access
- The activities of the United States Senate are a topic of interest for researchers and concerned members of the public alike. Websites such as GovTrack and Congress.gov allow people to research specific bills among many other offerings. However, they have significant weaknesses regarding their ease of use and the way they organize and store data. The Congressional Database Project aims to provide an intuitive user experience navigating government data while storing the data in a consistent database. We approach this project from an HCI perspective in order to determine the best ways to improve the user experience. We have conducted a qualitative user study to test the effectiveness of our design and identify potential areas of improvement. This paper provides an in-depth overview of the design of the Congressional Database on the front end and back end. It then explains the methodology of our user study and discusses the implications of its findings.
"Italianos por todos lados (Italians Everywhere)": Italian Immigrants and Argentine Exceptionalism Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2022-01-01
Creator: Julia Elisabeth Perillo
Access: Access restricted to the Bowdoin Community
The Roles of ROG1, REM1, and REM2 in a WAK Mediated Pectin Response Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2015-05-01
Creator: Joshua A Benton
Access: Access restricted to the Bowdoin Community
Digital Market Concentration: An Institutional and Social Cost Analysis
Date: 2022-01-01
Creator: Jack Shane
Access: Open access
- In this thesis, I develop an analysis of the industry concentration seen in digital markets today. I begin with a description and argument for the use of institutional economics. This framework allows for the integration of an interdisciplinary approach to economics. My analysis details the socioeconomic and political impacts, as well as the underlying market dynamics that have pushed digital markets towards concentration. I offer novel explanations for the lack of firm behavior that should theoretically increase profit, the existence of barriers to competition, and consumer behavior that focus on the role of social institutions. I also detail many of the social costs of these concentrated markets, such as their impact on democracy, power to influence social institutions, and the impact they have on concentration in other markets. This is done to show that the fears surrounding monopolies do not end with prices. Even in digital markets, where many times prices are very low, if not zero, there are reasons that monopoly is economically inefficient and socially sub-optimal. However, due to the path-dependent nature of the extreme benefits associated with digital markets, policymakers cannot reasonably propose breaking up these companies. Instead, they must use the power of the government to counteract the conglomerations of social power seen in these private companies in search of an optimal outcome.
From “a Journey for Peace” to the “Butchers of Beijing”: How Presidents have Used Rhetoric about China to Win the Two-Level Game
Date: 2021-01-01
Creator: Juliet Halvorson-Taylor
Access: Open access
- This thesis is an exploration of how American presidents have used rhetoric for strategic ends in the US-China relationship. Whenever a president speaks, he is speaking to multiple audiences at the same time, yet he also must balance a number of important considerations. I used Robert Putnam’s “Two-Level Game Theory” as a framework for understanding the conditions surrounding a moment of significance in US-China relations in order to decipher a president’s rhetorical choices. The project is divided into five main parts. First, I used the UCSB American Presidency Project to identify broad trends in rhetoric towards China across presidencies. I found that every president has spoken more about China than his predecessor since the 1980s and that presidents are increasingly using negative rhetoric when talking about China. Then, I conducted three case studies, within the Putnam framework, on important points in three presidencies: Truman’s decision to withdraw aid from the KMT, Nixon’s visit to China, and Clinton’s reversal on the issue of MFN status for China. Lastly, I concluded that when “win-sets” on both sides (in these examples: on both the American and Chinese sides) are either large or small, a president should speak about China more frequently. I also looked at Trump’s presidency and the beginnings of Biden’s in order to see how these trends are playing out currently.
Maïssa Bey : comment dire le traumatisme et la violence des guerres en Algérie Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2021-01-01
Creator: Anna Bosari
Access: Access restricted to the Bowdoin Community
Cultivating Community: Coastal Collaborations for Equitable Climate Survival and Adaptation in Rockland, Maine Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2021-01-01
Creator: Lily Andra McVetty
Access: Access restricted to the Bowdoin Community
Hot Boy Summer? Analyzing Managerial Reactions to Season-long Fluctuating Player Performance In Major League Baseball
Date: 2022-01-01
Creator: John Rodgers Hood
Access: Open access
- This paper suggests numerical weights that a Major League Baseball (MLB) manager may use when comparing player performance across multiple past performance periods to predict future performance. By the end of the MLB regular season, current season performance becomes more predictive than prior season performance for pitchers but not hitters. After estimating weights for different past time periods of performance, this paper compares the weights with how managers value performance in high-stakes situations across these same time periods. I find that MLB managers overreact to recent performance by both hitters and pitchers in postseason settings.
Enlightenment as Global History: The Reception of Confucianism in Eighteenth-Century France
Date: 2022-01-01
Creator: Rachel Yang
Access: Open access
- While the Enlightenment was once seen as a unique product of Western intellectual heritage, recent scholars have started to challenge this Eurocentric notion with the concept of a “global Enlightenment” by considering how it was shaped by cross-cultural encounters. To contribute to this body of scholarship, I trace the reception history of Confucianism in eighteenth-century France and examine how Chinese philosophy played a part in shaping and stimulating Enlightenment discourse. My research starts with the Jesuit missionaries who served as the intellectual intermediaries between China and Europe. Through a close reading of Confucius Sinarum Philosophus, a Latin translation of Confucian classics, I demonstrate how the Jesuits produced a Christianized reading of Confucianism that they could leverage for their spiritual and political ambitions. Then, I examine how some of the most notable figures of the French Enlightenment, such as Pierre Bayle, Voltaire, and Jean-Jacques Rousseau appropriated Confucian ideals to criticize religious orthodoxy and debate about subjects such as universalism, religious tolerance, and civilization. While the French thinkers mostly weaponized Confucianism for their own ends, their appropriation allowed this imported philosophy to become relevant in a new context and tangibly shape Enlightenment conversations. This understanding helps us see the Enlightenment as a junction, or even product, of a cross-cultural fertilization of ideas rather than an isolated European phenomenon.
The Forest Before Us: Storying the North Maine Woods Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2024-01-01
Creator: Lillyana Browder
Access: Access restricted to the Bowdoin Community
Role of Polycomb group proteins in regulation of eyes absent gene expression in Drosophila melanogaster This record is embargoed.
- Embargo End Date: 2027-05-16
Date: 2024-01-01
Creator: Joanne Du
Access: Embargoed
Effects of the plasticizer tributyl phosphate (TBP) on the intrinsic properties of mammalian lumbar motor neurons This record is embargoed.
- Embargo End Date: 2027-05-16
Date: 2024-01-01
Creator: Connor Joseph Latona
Access: Embargoed
The Scars of War: The Demonic Mother as a Conduit for Expressing Victimization, Collective Guilt, and Forgiveness in Postwar Japanese Film, 1949-1964
Date: 2017-05-01
Creator: Sophia Walker
Access: Open access
- Contemporary American viewers are familiar with the vengeful and terrifying ghost women of recent J-Horror films such as Ringu (Nakata Hideo, 1998) and Ju-On (Shimizu Takashi, 2002). Yet in Japanese theater and literature, the threatening ghost woman has a long history, beginning with the neglected Lady Rokujo in Lady Murasaki’s 11th century novel The Tale of Genji, who possesses and kills her rivals. Throughout history, the Japanese ghost mother is hideous and pitiful, worthy of fear as well as sympathy, traits that authors and filmmakers across the centuries have exploited. This project puts together four films that have never before been discussed together -- Kinoshita Keisuke's Shinsaku Yotsuya Kaidan (1949), Nakagawa Nobuo's Tokaido Yotsuya Kaidan (1959) Mizoguchi Kenji's Ugetsu (1953), and Shindo Kaneto's Onibaba (1964) -- and discusses them as four different iterations of the demonic mother motif, presented as a projection of the Japanese collective’s postwar uncertainty over both the memory of suffering during World War II and the question of personal culpability.
Women’s Bodies Between Market and State: Lineages of the Transnational Indian Surrogacy Industry Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2018-05-01
Creator: Shea Cristina Necheles
Access: Access restricted to the Bowdoin Community
An Output Sensitive Algorithm for Computing Viewsheds and Total Viewsheds on 2D Terrains Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2018-05-01
Creator: Andrew P Prescott
Access: Access restricted to the Bowdoin Community
Investigating the effect of Fuc-O-NAP on the glycosylation of Helicobacter pylori Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2024-01-01
Creator: Panhasith Ung
Access: Access restricted to the Bowdoin Community
"Cooperate with Others for Common Ends?": Students as Gatekeepers of Culture and Tradition on College Campuses
Date: 2017-05-01
Creator: Pamela Zabala
Access: Open access
- As colleges and universities have increased efforts to make their campuses more racially and ethnically inclusive, students of color still perceive their campuses as hostile spaces to racial and ethnic minorities. On the other hand, white students often feel as though their institutions do too much, leaving administrators to balance the interests of both groups. This thesis draws on archival, ethnographic, and interview data collected at Bowdoin College to examine the relationship between students and between students and administrators given the role of students as major agents of change on college campuses. I have found that when students feel threatened by institutional change, they go into crisis and create spaces of resistance on campus. Institutions are incapable or unwilling to find solutions that meet the needs of the various constituencies within the student body. Therefore, students and administration become locked in a power struggle that produces only surface-level institutional change rather than meaningful reform in the face of rising racial tensions.
Mathematical Modeling of the American Lobster Cardiac Muscle Cell: An Investigation of Calcium Ion Permeability and Force of Contractions
Date: 2014-05-01
Creator: Lauren A Skerritt
Access: Open access
- In the American lobster (Homarus americanus), neurogenic stimulation of the heart drives fluxes of calcium (Ca2+) into the cytoplasm of a muscle cell resulting in heart muscle contraction. The heartbeat is completed by the active transport of calcium out of the cytoplasm into extracellular and intracellular spaces. An increase in the frequency of calcium release is expected to increase amplitude and duration of muscle contraction. This makes sense because an increase in cytoplasmic calcium should increase the activation of the muscle contractile elements (actin and myosin). Since calcium cycling is a reaction-diffusion process, the extent to which calcium mediates contraction amplitude and frequency will depend on the specific diffusion relationships of calcium in this system. Despite the importance of understanding this relationship, it is difficult to obtain experimental information on the dynamics of cytoplasmic calcium. Thus, we developed a mathematical diffusion model of the myofibril (muscle cell) to simulate calcium cycling in the lobster cardiac muscle cell. The amplitude and duration of the force curves produced by the model empirically mirrored that of the experimental data over a range of calcium diffusion coefficients (1-16), nerve stimulation durations (1/6-1/3 of a contraction period), and frequencies (40-80 Hz). The characteristics that alter the response of the lobster cardiac muscle system are stimulation duration (i.e., burst duration), burst frequency, and the rate of calcium diffusion into the cell’s cytoplasm. For this reason, we developed protocols that allow parameters representing these characteristics in the calcium-force model to be determined from isolated whole muscle experiments on lobster hearts (Phillips et al., 2004). These parameters are used to predict variability in lobster heart muscle function consistent with data recorded in experiments. Within the physiological range of nerve stimulation parameters (burst duration and cycle period), calcium increased the cell’s force output for increased burst duration. For example, increased duration of stimulation increased the muscle contraction period and vice versa. In terms of diffusion, a slower rate of calcium diffusion out of the sarcoplasmic reticulum decreased both the calcium level and the contraction duration of the cell. Finally, changes in stimulation frequency did not produce changes in contraction amplitude and duration. When considered in conjunction with experimental stimulations using lobster heart muscle cells, these data illustrate the prominent role for calcium diffusion in governing contraction-relaxation cycles in lobster hearts.
Characterization of expression of Sema1a variants in high-plasticity areas of the Gryllus bimaculatus nervous system
Date: 2018-05-01
Creator: Sara Spicer
Access: Open access
- The well-conserved semaphorin family of guidance molecules is known to play multiple complex roles in directing the growth and orientation of dendrites and axons within the developing invertebrate central and peripheral nervous system. Additionally, the expression of select semaphorins is maintained within some highly plastic areas of the adult central nervous system, such as the mushroom bodies, where they are associated with guidance of newly-born neurons as well as with synapse formation and modification. Within the cricket species Gryllus bimaculatus, deafferentation of the prothoracic ganglia and subsequent dendritic rearrangement of the auditory interneurons is associated with fluctuations in the expression of transmembrane Sema1a and diffusible Sema2a. Here, we characterize the expression of two different variants of Gryllus Sema1a, termed Horch Sema1a and Extavour Sema1a, in tissues associated with both developmental neuronal guidance and adult structural plasticity: the embryonic limb buds, the mushroom bodies of the brain, and the non-deafferented adult prothoracic ganglion. Although we were unable to visualize the expression of Extavour Sema1a in any tissue, we demonstrate via phylogenetic analysis that both Sema1a variants have homologs in species across the Insecta class, suggesting that Extavour SEMA1a is a conserved protein sequence. We observe no expression of Horch Sema1a in the embryonic limb bud, and suspect that Extavour Sema1a, which has a high pairwise identity with Schistocerca Sema1a, could be facilitating guidance of the tibial pioneer neuron growth in the limb bud, along with Sema2a. In the adult brain, we observe a colocalization of Horch Sema1a and Sema2a in the mushroom bodies and in a vertical stripe across the calyx, which may be indicative of interactions between Horch SEMA1a and SEMA2a in maintaining synaptic plasticity and guiding newly-born Kenyon cells. We also report a colocalization of Horch Sema1a and Sema2a in the anterior and posterior of the prothoracic ganglia on the ventral side, in the region of auditory interneuron cell bodies, suggesting the possibility that auditory interneurons may express both Horch Sema1a and Sema2a, which could interact with each other or with Plexin receptors to regulate dendrite morphology at the midline.
An Investigation of Genetics-Based Machine Learning as Applied to Global Crop Yields Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2017-05-01
Creator: William Gantt
Access: Access restricted to the Bowdoin Community
Mythologies modernes : à la recherche des écrivaines dans la capitale littéraire de Paris de l’entre-deux-guerres This record is embargoed.
- Embargo End Date: 2029-05-16
Date: 2024-01-01
Creator: Stephanie Ruth McCurrach
Access: Embargoed
Examining the role of GRP and LIK1 in Wall Associated Kinase (WAK) perception of pectin in the plant cell wall
Date: 2017-01-01
Creator: Jack Ryan Mitchell
Access: Open access
- Wall associated kinases (WAKs) are cell membrane bound receptor kinases that bind pectin and pectin fragments (OGs).The binding of WAKs to pectin sends a growth signal required for cell elongation and plant development. WAKs bind OGs with higher affinity than native pectin and instead activate a stress response. Glycine rich proteins (GRPs) are secreted cell wall proteins of unknown function. Seven GRPs with 65% sequence similarity are coded on a 90kb locus of Arabidopsis chromosome 2. GRP3 and WAK1 have been shown to bind in vitro, but single null mutations have no discernible phenotype, suggesting that the GRPs are redundant. Low recombination frequency has made multiple mutations difficult to achieve, but in this thesis, CRISPR/Cas9 technology was used to induce deletions of the GRP locus. The promoters pYAO and pICU2 drove Cas9 expression in transformed Arabidopsis plants. The presence of a deletion and Cas9 were detected by PCR. While somatic mutations were induced, there was no inheritance of the GRP deletion, indicating that pYAO and pICU2 do not drive Cas9 to induce deletions in progenitor cells. LIK1 is a CERK1 interacting kinase implicated in mediating response to various microbe associated molecular patterns (MAMP) such as chitin, flagellin, and peptidoglycans. LIK1 exhibits a drastic increase in phosphorylation in response to OG treatment, making it a candidate for a co-receptor to WAK. T-DNA insertions to the 5’UTR of LIK1 were used to examine the effect of a lik1 mutation on the OG induced stress response. lik1/lik1 mutant seedlings were grown in the presence and absence of OGs, and RNA was isolated. qPCR was used on cDNA to examine FADLOX expression, a reporter for the transcriptional response to OGs. The lik1/lik1 mutant caused a reduction in the OG induced transcriptional response. However, increased LIK1 expression was associated with the T-DNA insertion indicating that LIK1 inhibits the WAK stress response pathway. Understanding the roles of GRP and LIK1 in moderating WAK mediated pathogenic response in Arabidopsis will enable a better understanding of plant resistance to pathogen invasion in the greater plant kingdom.
The Ethiopian Student Movement and the Dilemma of Eritrean Sovereignty
Date: 2024-01-01
Creator: Liat G. Tesfazgi
Access: Open access
- From the perspective of Ethiopian royalists, Pan-Africanists, Marxist internationalists, supports of union, and the broader international community, Eritrean nationalism revealed distressing fissures in many different arguments for preserving Ethiopian territorial unity– arguments not necessarily or explicitly problematic, but nevertheless in opposition to Eritrean demands for the right to national self-determination. For the Ethiopian Student Movement (ESM) specifically, Eritrean sovereignty demanded a reconfiguration of Pan-African unity that conflicted with Ethiopian exceptionalist historiography. Through an analysis of student politics at Haile Selassie University, from 1960-1974, this thesis seeks to complicate existing historiography on the ESM by examining the periodically divergent experiences of Eritrean student activists.
Self-Censorsh** in the Classroom This record is embargoed.
- Embargo End Date: 2027-05-14
Date: 2024-01-01
Creator: Sarah Greenberg
Access: Embargoed
Neural compensation in response to salinity perturbation in the cardiac ganglion of the American lobster, Homarus americanus
Date: 2024-01-01
Creator: Josephine P. Tidmore
Access: Open access
- Central pattern generator (CPG) networks produce the rhythmic motor patterns that underlie critical behaviors such as breathing, walking, and heartbeat. The fidelity of these neural circuits in response to fluctuations in environmental conditions is essential for organismal survival. The specific ion channel profile of a neuron dictates its electrophysiological phenotype and is under homeostatic control, as channel proteins are constantly turning over in the membrane in response to internal and external stimuli. Neuronal function depends on ion channels and biophysical processes that are sensitive to external variables such as temperature, pH, and salinity. Nonetheless, the nervous system of the American lobster (Homarus americanus) is robust to global perturbations in these variables. The cardiac ganglion (CG), the CPG that controls the rhythmic activation of the heart in the lobster, has been shown to maintain function across a relatively wide, ecologically-relevant range of saline concentrations in the short-term. This study investigates whether individual neurons of the CG sense and compensate for long-term changes in extracellular ion concentration by controlling their ion channel mRNA abundances. To do this, I bathed the isolated CG in either 0.75x, 1.5x, or 1x (physiological) saline concentrations for 24 h. I then dissected out individual CG motor neurons, the pacemaker neurons, and sections of axonal projections and used single-cell RT-qPCR to measure relative mRNA abundances of several species of ion channels in these cells. I found that the CG maintained stable output with 24 h exposure to altered saline concentrations (0.75x and 1.5x), and that this stability may indeed be enabled by changes in mRNA abundances and correlated channel relationships.
Understanding the Truce of the Irish War of Independence Through Regional Newspaper Editorials
Date: 2025-01-01
Creator: Janet Elizabeth Briggs
Access: Open access
Characterizing the organizational/activational role of ovarian hormones in the mediation of
adversity-induced anxiety in female rats Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Cassidy J. Scott
Access: Access restricted to the Bowdoin Community
Random Walks on Finite Groups: an
Application of Group Representations
Date: 2025-01-01
Creator: David Guan
Access: Open access
- Playing cards, a set of fifty-two cards with four suits and thirteen numbers, appear every- where in ourdaily lives. In particular, theyare commonly used ongambling tables in casinos. Before every game, the dealer needs to shuffle those cards to put them into a random order so that the game is fair. (Is it really the case in casinos?) One may wonder whether a shuffling technique is really efficient or not, i.e. whether it can turn the deck into a random configu- ration in a small number of rounds. Mathematically, this can be interpreted as a problem of random walks on the symmetric group of 52 elements S_{52} and we aim to determine how fast the random walk becomes (uniformly) random. This paper aims to explain an important application of group representations to this type of problems; in particular, techniques from group representations can provide a (roughly) accurate approximation. There will be six chapters in this paper. Chapter 1 is an introduction to problems of random walks. Chapter 2 and 3 discuss group representations in general, and a key lemma for application is discussed at the end of Chapter 3. Chapter 4 is an application to the easiest random walk one can encounter. Chapter 5 focuses on discussing properties distinctive to symmetric groups, and Chapter 6 discusses a card-shuffling example in details. Contents in Chapter 5 are mostly from the second chapter of [Sag01]; the key result in Chapter 6 along with the rest of the paper are mostly from [Dia88] with a few exceptions. This paper is written in a self-explanatory way, so anyone with necessary background of linear algebra, group theory, and probability will be able to follow the entirety of it.
Exploring the Effect of Core Tactics and Demographics on Squash
Gameplay Patterns Using Computer Vision
Date: 2025-01-01
Creator: Abhiroop Reddy Nagireddygari
Access: Open access
- This paper presents a computer vision system for analyzing common tactical and training pat- terns in squash using player locations and movement dynamics. Leveraging convolutional neural networks (CNNs) such as YOLO and TrackNet, we extract player coordinates on a squash court through a lightweight, single-camera framework. Match footage and detections are segmented by gender, skill level, and match phase to enable contextual comparisons. From 2D coordinates, we generate heatmaps of player locations, court coverage percentages, and distance-over-time graphs to visualize movement tendencies. Our results show that women demonstrate greater ball control and accuracy than men across all levels, while professional players exhibit more aggressive court usage than amateurs. We also identify that games 2 and 3 are the most physically demanding, highlighting a balance between slow starts and fatigue.
Tree Level Amplitudes for Yang-Mills and Complex Scalar Field Theory using Perturbiner Methods
Date: 2025-01-01
Creator: Abigail R. Chriss
Access: Open access
Associations between Autistic Camouflaging, Autistic Burnout, Authenticity, and Mental Health Challenges: Exploring A Mediation Model Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Yaerin H. Wallenberger
Access: Access restricted to the Bowdoin Community
Healthcare Practitioners as Educators: Perspectives on Preventing Sexual Violence
Date: 2025-01-01
Creator: Aidan N. Michelow
Access: Open access
Group-theory constraints on color-ordered five-point amplitudes in SU(N) and SO(N) gauge-theories Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Nathan Clay Bailey
Access: Access restricted to the Bowdoin Community
The Physiological Effects of Acute Exposure to MPTP on the Mammalian Lumbar Central Pattern Generator Network Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Ephraim Kyenkyenhene Boamah
Access: Access restricted to the Bowdoin Community
Honors Projects
- The honors project offers seniors the opportunity to engage in original scholarship under the supervision of a faculty member in their major department or program and results in a written thesis and/or oral defense, artistic performance or showing, depending on the student’s field of study.
Energy Policy is a Highway: Federal Energy Policy Evolution in the United States Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Chelsea Moody
Access: Access restricted to the Bowdoin Community
Out of Time: Queer Resistance to Chrononormativity in the Poetry of Emily Dickinson
Date: 2025-01-01
Creator: Elana Sheinkopf
Access: Open access
Demagogues of Disunion: The Role of Honor in Southern Secession Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2025-01-01
Creator: Evan Robert Cote Chapman
Access: Access restricted to the Bowdoin Community
La representación literaria y la construcción espacial de la pampa argentina – un
análisis de textos desde el siglo XIX hasta el XXI
Date: 2025-01-01
Creator: Kaitlyn Brunner
Access: Open access
- This paper analyzes the spacialization of the pampa in Argentine literature, both canonical works and contemporary ones. How is rurality and the Argentine countryside represented in these works? How do they expand upon or challenge each other? The immensity of the pampa and its vast plains has served as a focal point of fascination for various authors and Argentine political leaders, intimately related to ideas of frontier and progress. It has served as a site for various political dreams and agendas throughout history and presidential administrations, even to propel its own extermination project to assert dominion over the pampa and assassinate its own Indigenous people. The various conceptualizations of the pampa and the people who inhabit and care for the land—the gauchos and indigenous communities—demonstrate a larger dichotomy of the city and the urban versus the countryside and the rural, or as Sarmiento puts it—civilization and barbarie. The effort to tame the ‘wild’ pampa produces the immense projects of agricultural development that we see today, degrading the land and poisoning the bodies of rural people. More contemporarily, the spacialization of the city and the country in contemporary Argentine literature begins to subvert and defy the traditional binary thinking of the two spaces. I analyze Argentine literature from the 19th century to the 21st century to show how the locus of the pampa and other rural spaces has changed over time, showing the reconfiguration of the country’s landscape in literature.
GEM-PSO: Particle Swarm Optimization Guided by Enhanced Memory
Date: 2019-05-01
Creator: Kevin Fakai Chen
Access: Open access
- Particle Swarm Optimization (PSO) is a widely-used nature-inspired optimization technique in which a swarm of virtual particles work together with limited communication to find a global minimum or optimum. PSO has has been successfully applied to a wide variety of practical problems, such as optimization in engineering fields, hybridization with other nature-inspired algorithms, or even general optimization problems. However, PSO suffers from a phenomenon known as premature convergence, in which the algorithm's particles all converge on a local optimum instead of the global optimum, and cannot improve their solution any further. We seek to improve upon the standard Particle Swarm PSO algorithm by fixing this premature convergence behavior. We do so by storing and exploiting increased information in the form of past bests, which we deem enhanced memory. We introduce three types of modifications to each new algorithm (which we call a GEM-PSO: Particle Swarm Optimization, Guided by Enhanced Memory, because our modifications all deal with enhancing the memory of each particle). These are procedures for saving a found best, for removing a best from memory when a new one is to be added, and for selecting one (or more) bests to be used from those saved in memory. By using different combinations of these modifications, we can create many different variants of GEM-PSO that have a wide variety of behaviors and qualities. We analyze the performance of GEM-PSO, discuss the impact of PSO's parameters on the algorithms' performances, isolate different modifications in order to closely study their impact on the performance of any given GEM-PSO variant, and finally look at how multiple modifications perform. Finally, we draw conclusions about the efficacy and potential of GEM-PSO variants, and provide ideas for further exploration in this area of study. Many GEM-PSO variants are able to consistently outperform standard PSO on specific functions, and GEM-PSO variants can be shown to be promising, with both general and specific use cases.
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.
Lie to Me: Linguistic Markers of Deception in Relation to Individual Differences in Executive Control Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2014-05-01
Creator: Lauren Pashkowski
Access: Access restricted to the Bowdoin Community
"I Deny Your Authority to Try My Conscience:" Conscription and Conscientious Objectors In Britain During the Great War
Date: 2019-05-01
Creator: Albert William Wetter
Access: Open access
- During the Great War, the Military Service Act was introduced on January 27, 1916 and redefined British citizenship. Moreover, some men objected to the state’s military service mandate, adamant that compliance violated their conscience. This thesis investigates how the introduction of conscription reshaped British society, dismantled the “sacred principle” of volunteerism, and replaced it with conscription, resulting in political and popular debates, which altered the individual’s relationship with the state. British society transformed from a polity defined by the tenets of Liberalism and a free-will social contract to a society where citizenship was correlated to duty to the state. Building off Lois Bibbings’ research on conscientious objectors, this thesis nuances the analysis with the case studies of David Blelloch and Norman Gaudie. Framed by two theories—Benedict Anderson’s imagined community and Barbara Rosenwein’s emotional community—these case studies demonstrate how conscientious objectors exposed the incongruence of the British imagined and emotional community, and the redefinition of citizenship. By weaving these theories into the British Great War tapestry, this thesis contends that the British nation was imagined differently before the war than it was after the war because of the introduction of conscription. Drawing from parliamentary debate transcripts, newspaper articles, and archival material from the Imperial War Museum in London, and the Liddle Personal Collection at the University of Leeds, Blelloch’s and Gaudie’s respective case studies ultimately bait the question: “What does it mean to be British?”
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.
Using metabolic oligosaccharide engineering to induce immune-mediated cell killing of bacterial pathogens Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Brendan H. Pulsifer
Access: Access restricted to the Bowdoin Community