IDA Mount Holyoke College Institutional Digital Archive
Not a member yet
1794 research outputs found
Sort by
Star Formation and AGN Feedback in the Local Universe: Combining the Radio Continuum and Integral Field Spectroscopy
No full textThe effect of active galactic nuclei (AGN) on their host galaxies-in particular their star formation rates (SFRs)-remains one of the key outstanding questions of galaxy evolution. Although successful cosmological models of galaxy evolution require a fraction of an AGN's released energy to be redistributed into the interstellar medium to reproduce massive galaxies, direct evidence of AGN winds, jets, or radiation enhancing or quenching star formation through heating, cooling, or redistributing gas is rare. Typically, AGN jets can only be identified at radio frequencies. Therefore, we take advantage of the unique capabilities of the LOw Frequency ARray (LOFAR), which can detect synchrotron emission from such jets in fainter AGN than possible in previous wide-field surveys. The radio-continuum coupled with integral field spectroscopy (IFS), which allows for the spatially resolved study of the properties of stellar populations and nebular gas, is a potent combination for studying the effect of AGNs on their host galaxies. By combining data from the LOFAR Two-meter Sky Survey (LoTSS) with data from one of the largest optical IFS surveys, Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), we probe 338 local (z < 0.15) galaxies that host radio-loud AGN (RLAGN). We compare our results to a robust control sample of non-active galaxies that match the stellar mass, redshift, visual morphology, and inclination of the RLAGN host. To identify the effect of AGN feedback on the star-forming (SF) properties of their host galaxies, we focus on several principal questions:
1. How does the distribution of SFRs in regions ionized by hot stars for RLAGN and control galaxies compare?
2. Where in relation to the SF main-sequence (SFMS) do RLAGN and control galaxies lie?
3. How does the age of stellar populations in RLAGN and control galaxies change with increasing galactocentric distance?
To investigate the first question, we use MaNGA data to spatially resolve the ionizing mechanisms of gas across the surface of each RLAGN and control galaxy. In regions excited primarily by SF activity, we use the extinction corrected luminosity of Hα as a tracer of SFR. We then rely on integrated and gradient properties from the MaNGA Pipe3D value added catalog to address our final two questions. On the whole we find no significant difference between RLAGN and control galaxies, which could indicate that AGN have no overall effect on their host galaxies, or that any effect that the jets have cannot be seen yet. Larger sample sizes observed at multiple frequencies and high resolution images are needed in order to overcome the uncertainties in the visibility of AGN feedback and the spatial scale at which these interactions occur, respectively. Further work will be needed to decompose the radio emission into that coming from SF and that from AGN jets, which is important for reliable estimates of jet power and comparison to theoretical models.Astronom
The Age and Petrogenesis of a Sillimanite Gneiss within the Belchertown Igneous Complex, Massachusetts
No full textThis study applies chemical dating of monazite following the methods of Williams et al. (2017) in samples from a septum of metapelite that lies within the Belchertown intrusion in central Massachusetts. This septum is identified as Partridge Formation sillimanite schist that is characterized by large (10 cm long) sillimanite porphyroblasts interpreted to be pseudomorphs after andalusite in previous studies. Three samples (BE17-2, PF-2, and MAR20-1) were collected from an outcrop on the southern end of the septum. Whole rock composition data for these samples was obtained from XRF analysis. Individual monazite grains were identified by compositional mapping of thin sections with the electron microprobe at UMass. Individual monazite grains were mapped for Y, Th, and other elements and chemical domains were identified. Complete chemical analysis of selected domains was conducted and an age was calculated following the methods of Williams et al. (2017). Pseudosections detailing P-T stability fields for these samples were generated using Theriak Domino and the whole rock composition data. The estimated pressure of stability for all three samples is greater than 5 kbar. The temperature stability range for one staurolite-containing sample is estimated to be 500-700°C, and for the other staurolite-lacking samples, the temperature range is greater than 650°C. The majority of monazite grains in all three samples give an age of ~370 Ma, which corresponds to the Neo-acadian orogeny and metamorphism in central Massachusetts (Robinson et al., 1998). A few grains from two samples give much younger dates of ~280 Ma, which dates to the Alleghanian orogeny. Highly irregular, patchy textures in Y composition maps of these grains are interpreted to be the result of a fluid-mediated alteration event. Fluid alteration would reset the U-Th-Pb system, leading us to conclude that the fluid alteration event would have occurred during the older Neo-acadian event.Geolog
From Bathroom Stalls to "Born This Way": The Rise and Fall of the Punitive Sexuality Regime in 20th Century America
No full textHow does policy affect identity? This thesis uses the theories of American Political Development to analyze the effects of government action on the identities of citizens, specifically focusing on how policy regimes can structure the lives of citizens. Using the development of the punitive sexuality regime of the 20th century as a case study, I argue that the rapid change in the societal status of gay Americans from the late 20th century to the present is the result of government policy shaping both gay identity and political perceptions of homosexuality in such a way that eventually there was a break in the regime. I trace the development of the regime from its inception in the years prior to World War II to its apogee during the Lavender Scare. This regime was dependent upon the way in which it silenced gay Americans limiting their ability to advocate for their rights. I argue that the AIDS crisis constituted a break in the regime because the deadly nature of the disease meant that being openly gay and fighting for an adequate government response was more important than any benefits which might come from being closeted. Finally, I analyze the present state of LGBT rights and the status of gay Americans in light of the formation of a new sexuality regime.Politic
Continuity and Growth Mechanism of Polydopamine Thin Films
No full textWith their ability to adhere to a wide variety of underwater surfaces, mussels have inspired a new line of investigation into surface chemistry and adhesives. This unique ability is due to byssal threads that mussels excrete, composed of proteins with a high concentration of the amino acid 3,4-dihydroxyphenlalanine (DOPA). Dopamine (DA), a small molecule mimic of DOPA, is able to polymerize under oxidizing conditions. Polydopamine (PDA) is known as a universal adhesive, although its adhesive properties are affected by many different experimental variables, including pH, buffer type, oxidizing agent, substrate, and coating method. Previous research in the Chen lab has determined the optimized conditions for spin coating PDA. These include DA concentration of 4 mg/mL, sodium periodate (SP) as the oxidizing agent with [SP]:[DA] = 2, 0.25 M pH = 6 acetate buffer, and 1 min adhesion time prior to spin.
This project focuses on the differences in PDA adhesion on substrates with varying functional groups. PDA is able to form many different chemical interactions, but it is limited by the chemistry of the substrate. This project examines PDA adhesion on native silicon wafers (SiO2) and substrates containing polydimethylsiloxane (PDMS) and aminopropyl methylsiloxane – dimethylsiloxane copolymer (PADMS). PDMS and PADMS are chemically similar; however, continuous PDA morphology is obtained on SiO2 and PADMS, while the PDA films contain cracks on PDMS. When PDMS and PADMS polymers were mixed to form composite substrates, only a minuscule fraction of PADMS, 1/20,000, is required for the morphology of the adhered PDA film to utilize the same growth mechanism as that on pure PADMS. In order to form a continuous film on pure PDMS, the buffer solution was diluted to reduce interference from salt ions.
Dip coating is the traditional method of PDA film deposition; however, the research for this project was conducted using spin coating. Therefore, a modified dip coating method was created in order to ensure that any conclusions drawn from this research would be relevant for both spin and dip coating. Additionally, in an attempt to extend the lifespan of PDA solutions, the pH was lowered at the aging time with the most adhesive particles in solution. This would theoretically halt additional polymerization and allow one PDA solution to be used multiple times.Chemistr
Mount Holyoke College: Introduction in Japanese
No full textThis newsletter was created by four students (Lewis, Lennon, Quinn, Zhang) in Asian 326 Third-year Japanese II in the spring semester of 2021 (Module 2) with a guest writer from Japan (Hoshino). It introduces Mount Holyoke College from students' point of view for Japanese audience. Edited by Naoko Nemoto
Analyzing Impacts of Multiple Environmental Variables on Minuca pugnax Behavioral Thermoregulation
No full textThe salt marsh dwelling fiddler crab Minuca pugnax is an intertidal ectotherm that navigates an environmentally variable habitat through using burrows for behavioral thermoregulation. Behavioral thermoregulation in fiddler crabs is impacted by multiple environmental variables. In this study, I examined the impacts of surface and burrow temperatures, density of conspecifics, and tidal height on duration of burrow retreat and surface activity in male M. pugnax. I analyzed video, temperature, and tidal height data recorded on Sapelo Island, GA in August 2019 and developed linear regression models informed by correlation analyses. I found that the duration of surface activity was impacted by changes in surface temperature, burrow temperature, and density of conspecifics. As surface temperature increased, the duration of surface activity decreased. As density of conspecifics increased, duration of surface activity also increased. However, density and surface temperature were correlated. The duration of burrow retreat was not impacted by any environmental variable. The average duration of burrow retreat was much shorter and more consistent than the average duration of surface activity, suggesting that crabs cool rapidly in burrows. These preliminary data illustrate the complex relationship between M. pugnax and its salt marsh environment.Biological Science
Manifestations of the Gothic in Jewish Literature
No full textThe Jewish experience is a prime landscape for the gothic to erupt. Our constant instability as a people—our homelessness, our oppression, our ancestry—is ripe for a gothic reading. I found that the Jewish gothic predicates itself not on original sin, but on a sense of moral responsibility that manifests in values such as tikkun olam and tzedakah. It is obsessed with generational trauma, the desire and inability to have a home, who gets to speak, and the slow degradation of tradition. Many of these anxieties can be found in two emblematic figures of the Jewish gothic, the dybbuk and the golem. Both consider repressed voices, unearth the oppression of women, and question traditional religious rules, all within specifically Jewish contexts. I utilized these aspects in the writing of two short stories that manifested my understanding of the Jewish gothic. In the end, I learned that while the Jewish gothic shares many similarities with the inherent tropes of the gothic genre found in European literature, the perpetual and ancestral fear contained within the Jewish community manifests a gothic canon with its own twists and turns.Englis
STUDY OF CONDITIONS FOR METASTABLE POLY(VINYL ALCOHOL) THIN FILMS ON POLYDIMETHYLSILOXANE SUBSTRATES
No full textChemistr
Coordination of Persistent Multi-Robot Formations
No full textIn collective transport, a search and rescue multi-robot formation must preserve its shape in order to safely carry an object from one location to another. In this thesis we focus on persistent acyclic leader-follower formations in which robots adhere to local pairwise distance constraints in order to maintain the formation as a whole. We rely on combinatorial rigidity and persistence theory, where robots are modeled as vertices and distance constraints as edges. In order to identify the formations that perform best, we define a property called diameter using the concept of waves. We hypothesize that diameter impacts the performance of a moving formation. By generating persistent acyclic leader-follower formations, we design a set of experiments both on simulation and on a multi-robot hardware platform. The results and analysis support our hypothesis that smaller diameter is related to better performance.Computer Scienc
Examining Vocabulary Acquisition Through Incidental Reading and a Morphological Awareness Intervention
No full textThis project investigates multiple factors that contribute to adult vocabulary acquisition and how they work together. Word morphology and the number of exposures to words are examined, as well as the impact of varying affixes of words across exposures. Tests measuring participants’ depth and breadth of vocabulary knowledge were administered prior to the reading exercises in this study, and these differences are explored along with the other variables. Finally, the project addresses the potentiality that adults can benefit from direct learning about word structure in the way that adolescents do in language classes. Half of participants engaged in a series of short activities that explicitly taught them about morphology, while half did not. Results revealed that accuracy was higher for words with one morpheme than words with multiple morphemes, and also higher for words with multiple exposures than words with only one exposure. In addition, participants who scored higher on the vocabulary depth and breadth measures also scored higher on the accuracy test. These results hold implications for ways that adults can best be aided in expanding their vocabularies.Psychology & Educatio