Honors Projects
Showing 51 - 60 of 298 Items
Characterization of Yellow Family Proteins in Gryllus bimaculatus
Date: 2021-01-01
Creator: Alexandra W. Rubenstein
Access: Open access
- Neuronal plasticity occurs in developing nervous systems, with adult organisms rarely able to recover from neurological damage. The cricket, Gryllus bimaculatus, is useful to study neuronal plasticity due to its reorganization of the auditory system in response to injury beyond development. When a cricket ear is removed and auditory afferents severed, a rare phenomenon occurs: the dendrites of interneurons on the deafferented side cross the typically-respected midline of the prothoracic ganglion to form functional synapses with auditory afferents from the opposite side. To find proteins involved in this phenomenon, the Horch Lab assembled a de novo transcriptome from neurons in the prothoracic ganglion of G. bimaculatus. Differential gene expression analysis revealed upregulated protein yellows post-deafferentation, indicating these proteins could influence neuronal plasticity in the adult cricket CNS. I focused on characterizing the protein yellow family in the cricket. By relating protein yellows evolutionarily, mapping them onto the genome, and analyzing their sequences, I discovered the cricket has 10 yellow genes, including a newly identified yellow-r* and a block of yellows showing synteny with insect genomes. Additionally, yellow-e and -x in crickets are closely related to bacterial yellow, perhaps indicating a role for horizontal gene transfer in yellow gene evolution. The protein upregulated in the cricket CNS is closely related with yellow-f’s in other insects, indicating yellow-f is likely a secreted protein, highly expressed in the CNS, multifunctional, and conserved across insects. Characterizing yellow-f can give insight into how these upregulated proteins might be related to neuronal plasticity in G. bimaculatus.
Semaphorin-Induced Plasticity in the Nervous System of the Cricket, Gryllus bimaculatus
Date: 2021-01-01
Creator: Alicia G. Edwards
Access: Open access
- The adult auditory system of the cricket, Gryllus bimaculatus, exhibits a rare example of neuronal plasticity. Upon deafferentation, we observe medial dendrites that normally respect the midline of the PTG in the central nervous system sprouting across the boundary and forming synaptic connections with the contralateral auditory afferents. The Horch Lab has investigated key molecular factors that might play a causal role in this paradigm. Specifically, the protein Sema1a.2 comes from a guidance molecule family and has a role in developmental neuronal plasticity in other organisms. In this study, I explored the role of Sema1a.2 in the neuronal plasticity of the adult auditory system of the cricket by conducting a series of dsRNA knockdown experiments targeting Sema1a.2 followed by backfill procedures in which we iontophoresed dye into the Ascending Neurons (ANs) to visualize the anatomical effects of the knockdown experiments using confocal microscopy. We found that there were no significant differences between animals injected with dsRNA against GFP and Sema1a.2 volume, with respect to qualitative and quantitative data. However, we believe with an increase in cohort size, the trends observed, particularly the effect of Sema1a.2 knockdowns on CWM and CBM volumes, will become more pronounced and significant. Potential future pathways could include conducting double knockdowns of Sema1a.2 and Sema2a to observe if these two proteins are working together to create a more obvious effect on midline crossing and branching. Other options also include looking into other protein families that might be the causing factor in this rare phenomenon (toll-like receptors).
Characterizing the influence of Atlantic water intrusion on water mass formation and primary production in Kongsfjorden, Svalbard
Date: 2015-05-01
Creator: Courtney Michelle Payne
Access: Open access
- With warming global temperatures and changes to large-scale ocean circulation patterns, warm water intrusion into Arctic fjords is increasingly affecting fragile polar ecosystems. This study investigated how warm Atlantic water intrusion and the tidewater glacial melting it causes impacted water mass formation and primary productivity in Kongsfjorden, Svalbard. Data were collected over a 2-week period during the height of the melt season in August near the Kronebreen/Kongsvegen glacier complex, the most rapidly retreating glacier in Spitsbergen. Since 1998, intruding waters have warmed between 4 and 5.5˚C, which has prevented sea ice formation and changed the characteristics of fjord bottom waters. Increased glacial melting in the last decade has changed the characteristics of surface waters in the fjord. Modeled light fields suggest that suspended sediment in this glacial meltwater has reduced the euphotic zone close to the ice face, preventing high primary production in both the consistent and intermittent sediment-laden meltwater plumes. However, measurements collected close to terrestrially terminating glaciers indicate that extremely high primary production can occur in conditions of low turbidity. The results of this study support a three-part model of the effects of warm-water intrusion on water mass formation and primary production, where changes in sea ice coverage and tidewater glacial dynamics affect the optical light field. This model allows for spatial predictions for the most likely impacts of warm water intrusion on primary production in Spitsbergen, and could be extrapolated out to explore potential phytoplankton response in other regions susceptible to warm-water intrusion.
Tradition et Nouveauté: Une étude du baccalauréat et de la réforme Blanquer
Date: 2020-01-01
Creator: Fiona Carey
Access: Open access
- The baccalauréat exam has played a significant role in the lives of French high schoolers for more than two centuries. Not only does the exam determine a student’s eligibility for university, it is a long-standing national tradition and an important aspect of French identity. The baccalauréat consists of a core curriculum and a choice of specialties, all of which prepare students for the exams that they will take in their last two years of high school. In 2018, Minister of Education Jean-Michel Blanquer announced a reform to the baccalauréat that would drastically alter the content and structure of the exam. Blanquer’s reform offers students a wider variety of specialties and in doing so hopes to eliminate the supposed hierarchies which have historically valued sciences over other subject matters. This reform revolutionizes the system while simultaneously remaining deeply rooted in tradition. While Blanquer’s reform introduces changes to the core curriculum and an entirely new list of specialties, it preserves other aspects of the French education system, particularly the mandatory study of philosophy. This thesis examines the contrasting novelty and tradition of Blanquer’s baccalauréat. In order to understand the intent and implications of his reform, this thesis studies a series of historic reforms, provides a detailed explanation of Blanquer’s changes, and finally discusses a selection of anonymous survey responses concerning its potential impacts. In discussing these survey responses, I highlight three main themes: (1) hierarchies and freedom of choice, (2) collectivity and individuality, and (3) the role of nationalism in the baccalauréat.
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.
Caring like a state: The elaboration of a care ideology in Peru and Sri Lanka in the 20th century
Date: 2015-05-01
Creator: Katharine Herman
Access: Open access
- This project compares the interaction between the government and the population in both Peru and Sri Lanka through the 20th century, focusing on the provision of care (services, benefits, and recognition as provided by the governing apparatus) as a locus for their most meaningful interaction. The provision of care can be seen as a form of communication established in certain practices, symbols, and discourses. Moreover, the provision of care works to reorient the subject population into a more beneficial relationship with the state–notably one of increased dependence and trust. Through the elaboration of what care is and how it functions, a care ideology is established creating a terrain through which the politics of the governed and the governing alike can be legitimized. Care ideology can then be considered a further articulation of the state idea, creating a dialogue about how governance can or should be affected within a certain context. These case studies then illustrate the terrain over which both of these governing bodies work. In Sri Lanka, the governing apparatus provides a means for citizens to live a symbolically meaningful life through paddy farming. In Peru, the governing apparatus provides access to the state through civil infrastructure like roads and education. Through care, material goods become invested with meaning and the state idea becomes materialized. Care is a then substantial project undertaken by the state to ensure its own reproduction and further widen the possibilities for the state project to be effected through its own citizens.
Accretion Onto a Black Hole at the Center of a Neutron Star: Nuclear Equations of State
Date: 2022-01-01
Creator: Sophia Christina Schnauck
Access: Open access
- A recent re-examination of Bondi accretion (see Richards, Baumgarte and Shapiro (2021)) revealed that, for stiff equations of state (EOSs), steady-state accretion can only occur for accretion rates exceeding a certain minimum. To date, this result has been explored only for gamma-law equations of state. Instead, we consider accretion onto a small black hole residing at the center of a neutron star governed by a more realistic nuclear EOS. We generalize the relativistic Bondi solution for such EOSs, approximated by piecewise polytropes, and thereby obtain analytical expressions for the accretion rates which were reflected in our numerical simulations. After taking several different piecewise EOSs at different neutron star densities into account, the accretion rates of the different EOSs were only slightly larger than the previously observed minimum. In other words there appears to be evidence for a nearly universal accretion rate that depends only on the black hole mass. However, we also observed that for certain densities the fluid profiles of several EOSs exhibited superluminal sound speeds outside the horizon of the black hole, suggesting that the EOSs are not appropriate at these densities.
Jigs, Reels, and “Realness”: An Investigation of Ideas of Authenticity and Tradition in New England French Canadian Music
Date: 2021-01-01
Creator: Lowell Ruck
Access: Open access
- Franco-American culture is increasingly recognized as an integral part of the heritage of Maine and New England, and has attracted growing academic attention in recent years. But while many scholars and cultural promoters focus on the French language in their work on this subject, few studies have considered the position of traditional music in Franco-American communities in the 21st century. This thesis examines French Canadian traditional music as it is played in New England and the ways in which musicians think about authenticity and tradition in their art. Using material from ethnographic interviews, it illuminates how musicians draw from individual, familial, and communal experiences and from past, present, and future conceptions of authentic tradition in their roles as cultural mediators. Ultimately, it suggests that players of French Canadian traditional music interact with this tradition in diverse ways, and that in doing so, they help to maintain the vibrancy of Franco-American cultural practices. La culture franco-américaine est reconnue de plus en plus comme partie intégrante de l’héritage du Maine et de la Nouvelle-Angleterre et attire maintenant l’attention académique. Mais même si beaucoup d’érudits et de promoteurs culturels ciblent la langue française dans leur travail sur ce sujet, peu d’études ont considéré la position de la musique traditionnelle dans les communautés franco-américaines du XXIe siècle. Cette thèse se concentre sur la musique traditionnelle canadienne-française de la Nouvelle-Angleterre et sur les façons dont les musiciens conceptualisent l’authenticité et la tradition dans leur art. En utilisant des entrevues ethnographiques, elle illumine comment les musiciens tirent des expériences individuelles, familiales et communautaires et des idées du passé, du présent et de l’avenir dans leurs rôles comme médiateurs culturels. Finalement, elle suggère que les joueurs de la musique traditionnelle canadienne-française interagissent avec cette tradition de plusieurs façons, et ce faisant, aident à maintenir la brillance des pratiques culturelles franco-américaines.
The Photocatalytic Degradation of Ibuprofen and Atenolol Using Bismuth Oxychloride and Titanium Dioxide
Date: 2021-01-01
Creator: Kamyron Anthony Speller
Access: Open access
- Pharmaceuticals and personal care products (PPCPs) are contaminating natural bodies of water and are problematic for aquatic organisms and ecosystems. Generally, PPCPs are introduced to water systems due to incomplete removal by wastewater treatment plants (WWTPs). As such, it is vital to find ways to remediate these problematic contaminants before they are discharged into the environment. In this study, two photocatalysts¾titanium dioxide (TiO2) and bismuth oxychloride (BiOCl)¾were compared to determine their relative efficiencies (degradation rates) and dominant degradation mechanism (hydroxyl radical production or direct oxidation) with the goal of photocatalytically degrading two pharmaceuticals, atenolol and ibuprofen, using UV (254 nm) light. While TiO2 has been used extensively for photocatalytic degradation, BiOCl is a newer photocatalyst. The two pharmaceuticals selected for study represent two large classes of drugs (aryloxypropanolamine and propionic acid derivatives, respectively) that have been detected in the influent into and effluent from wastewater treatment plants and in the environment. When irradiated at 254 nm, BiOCl degrades ibuprofen with a rate constant 15 times greater than TiO2. On the other hand, TiO2 degrades atenolol with a rate constant 2.2 times greater than BiOCl. LCMS analysis of photodegradation products reveals different products produced by the two photocatalysts, providing evidence for the dominance of different degradation mechanisms for the two photocatalysts. In summary, this work suggests that BiOCl, potentially used in combination with TiO2, holds potential for degrading PPCPs in natural bodies of water.
Critical Phenomena in the Gravitational Collapse of Electromagnetic Dipole and Quadrupole Waves
Date: 2021-01-01
Creator: Maria F. Perez Mendoza
Access: Open access
- We report on critical phenomena in the gravitational collapse of electromagnetic waves. Generalizing earlier results that focused on dipole electromagnetic waves, we here compare with quadrupole waves in axisymmetry. We perform numerical simulations of dipole and quadrupole wave initial data, fine-tuning both sets of data to the onset of black hole formation in order to study the critical solution and related critical phenomena. We observe that different multipole moments have different symmetries, indicating that the critical solution for electromagnetic waves cannot be unique, at least not globally. This is confirmed in our numerical simulations: while dipole data lead to a single center of collapse, at the center of symmetry, quadrupole data feature two separate centers of collapse on the symmetry axis, above and below the center of symmetry -- reminiscent of similar findings reported for critical collapse of vacuum gravitational waves. While the critical solution for neither the dipole nor the quadrupole data is exactly self-similar, we find that their approximate echoing periods appear to differ, as do the critical exponents. We discuss whether the centers of collapse found for dipole and quadrupole data might all have the same properties, which would suggest a ``local uniqueness" of the critical solution. Instead, we provide some evidence -- including the differing echoing periods and critical exponents -- suggesting that the critical solutions are distinct even locally. We speculate on the implications of our findings for critical phenomena in the collapse of vacuum gravitational waves, which share with electromagnetic waves the absence of a spherically symmetric critical solution.