Showing 531 - 540 of 2039 Items
Geochemical and Stratigraphic Analysis of the Linnévatnet Sediment Record: A Study of Late Holocene Cirque Glacier Activity in Spitsbergen, Svalbard
Date: 2014-05-01
Creator: Graham Harper Edwards
Access: Open access
- Morainal and lacustrine sediments in Linnédalen, Spitsbergen, Svalbard, record the fluctuations of a glacier in a currently unglaciated mountain cirque during the Little Ice Age (LIA). This study attempts to reconstruct Late Holocene glacial activity within this cirque from geochemical, physical, and visual stratigraphic variation of the Linnévatnet lacustrine sediment record. A 57 cm lacustrine sediment core (D10.5) from Linnévatnet was analyzed at a high-resolution for variations in X-Ray Fluorescence (XRF)-measured elemental composition, spectral reflectance, and magnetic susceptibility. The visual stratigraphy was observed at a microscopic scale. An age-depth model for D10.5 is developed by extrapolating sedimentation rates from dated horizons, measured by 239+240Pu radionuclide fallout dating and chemostratigraphic enrichment of atmospheric anthropogenic pollutants. Visual stratigraphy of the sediment record indicates two periods of cirque glacier sediment delivery to Linnévatnet during the LIA (1329-1363 CE, 1816 CE-Present) and a third period of sediment delivery during the Medieval Climate Anomaly (MCA; 984-1082 CE). During non-glacial periods, stratigraphic variation in XRF-measured Ti and K appear to be associated with fluctuations in North Atlantic Oscillation (NAO)-regulated precipitation. Within the LIA glacial intervals, decadal-scale variations in sediment Ti and K geochemistry may result from advance and retreat of the cirque glacier ice-margin or fluctuations in precipitation. Stratigraphic variation in Fe content indicates complex erosional and hydrological processes associated with MCA precipitation and glacial meltwater. Stratigraphic and geochemical variations in the lacustrine record of Linnévatnet indicate that both cirque glacier activity and sediment transport in Linnédalen are more sensitive to climatological change than previously thought.
Seize the Memes: Community, Personal Expression, and Everyday Feminist Politics Through Instagram Memes
Date: 2018-01-01
Creator: Tessa Westfall
Access: Open access
ALGOrhythms: Leveraging Markov Chain-Based Generation of Functional Harmonies with User-Defined Musical Corpus as a Compositional Tool
Date: 2021-01-01
Creator: Coleman Brockmeier
Access: Open access
- Music forms the soundtrack to daily life and serves as an important cultural marker for people around the world. As the world becomes digitized and connected via the internet, the opportunity is increasingly accessible for anyone to share music with the world and to create chart-topping music that defines the cultural vernacular. Many prominent producers have little to no formal musical training, especially in Western music theory. As a result, loop-based music dominates the lists of most-played music on the radio and streaming services, often not deviating from basic functional harmony. With this project, I have created a compositional tool in the form of an iOS app which identifies the harmonic “fingerprint” behind a given set of songs. The app then leverages this understanding to create sequences of chords in the style of that fingerprint. To accomplish this, the app employs web scraping to create a corpus of musical information in the form of Markov chains — a transition table which underlies the data set. I introduce the idea of musical “chunks” defining a harmonic “fingerprint” and various methods of traversing the transition table to create chord progressions employing the fingerprint as a guide. The tool allows for specification of corpus, chunk size, traversal method, and the ability to listen to, share, and save generated results. The resulting app is a tool that allows the user to answer the question: “What would happen if Stevie Wonder and Billie Eilish wrote a song together?”
Economic Analysis of the Critical Habitat Designation Process for Endangered and Threatened Species Under the Endangered Species Act of 1973
Date: 2022-01-01
Creator: Katherine Fosburgh
Access: Open access
- Habitat destruction is the leading cause of biodiversity loss in the US. Under the Endangered Species Act (ESA), habitat deemed essential to endangered and threatened species recovery is proposed as critical habitat (CH). CH areas are subject to regulations that could alter land development plans or increase costs. The potential economic opportunity cost created by CH regulations may lead to the exclusion of land proposed for CH designation, thereby reducing the conservation benefits of the CH rule. In this paper, I use a unique dataset collected from Federal Register (FR) documents to estimate the reduction in CH acreage from proposed to final ruling, both on the extensive and intensive margin. I find a negative relationship between the level of household income in an area proposed for CH and the probability that a CH gains acreage or maintains acreage during the establishment process. I also find some evidence that higher household income in a CH area is associated with a greater relative loss in acreage between proposal and finalization. I also find that private land proposed for CH designation is less likely to be in the final designation than federal land. Overall, my results suggest that economic considerations influence CH allocation decisions. Whether reducing the amount of private land subject to CH designations is socially efficient depends on the unknown economic benefit of private land exclusions versus the cost of biodiversity and ecosystem service loss that may result from not protecting all land deemed vital to species recovery.
Teaching Computers to Teach Themselves: Synthesizing Training Data based on Human-Perceived Elements
Date: 2019-05-01
Creator: James Little
Access: Open access
- Isolation-Based Scene Generation (IBSG) is a process for creating synthetic datasets made to train machine learning detectors and classifiers. In this project, we formalize the IBSG process and describe the scenarios—object detection and object classification given audio or image input—in which it can be useful. We then look at the Stanford Street View House Number (SVHN) dataset and build several different IBSG training datasets based on existing SVHN data. We try to improve the compositing algorithm used to build the IBSG dataset so that models trained with synthetic data perform as well as models trained with the original SVHN training dataset. We find that the SVHN datasets that perform best are composited from isolations extracted from existing training data, leading us to suggest that IBSG be used in situations where a researcher wants to train a model with only a small amount of real, unlabeled training data.
The Politics of Land Rights in the Transition to Democratic South Africa: The Rise and Fall of the Constitutional Property Clause
Date: 2019-05-01
Creator: Anna Louisa Roosevelt Lennon
Access: Open access
Performing Sor Juana: Reimagining a Mexican Literary Figure in the 21st Century
Date: 2020-01-01
Creator: Uriel López-Serrano
Access: Open access
- Sor Juana Inés de la Cruz (c. 1648-1695) was a Mexican nun, poet, playwright, and scholar from the colonial era. She has become an icon for various global, social, and political movements. This project looks at four dramatic works created by Sorjuanistas who reimagine Sor Juana’s story for contemporary audiences living in the United States. The works included in this essay are Estela Portillo-Trambley’s Sor Juana (1986), Karen Zacarías’s The Sins of Sor Juana (2001), and Alicia Gaspar de Alba’s “Interview with Sor Juana Inés de la Cruz” (1998/2014) and her newest work, Juana: An Opera in Two Acts (2019), libretto by Carla Lucero. In addition to reimagining Sor Juana’s story, these dramatic works expose the sexism, racism, and xenophobia perpetuated by U.S institutions of power that discriminate against Latin@ and Chican@ individuals. By shedding light on the social injustices that existed during the colonial era, an embodied Sor Juana teaches audiences how to resist and mobilize against such oppressive powers. Sor Juana’s narrative on stage is necessary because she is a role model for Latin@s/Chican@s. Sorjuanistas remind us that the body can be used to retell the narratives of the silenced individuals who are victims of oppression. By developing heritage performances, Sorjuanistas challenge histories that silence and overlook social injustices. Witnessing Sor Juana on stage triggers emotional responses to the past which allow historical actors to obtain intellectual, emotional, and political agency in an effort to affirm and remember particular contemporary and future commitments to fighting social injustices.
Classifying Flow-kick Equilibria: Reactivity and Transient Behavior in the Variational Equation
Date: 2020-01-01
Creator: Alanna Haslam
Access: Open access
- In light of concerns about climate change, there is interest in how sustainable management can maintain the resilience of ecosystems. We use flow-kick dynamical systems to model ecosystems subject to a constant kick occurring every τ time units. We classify the stability of flow-kick equilibria to determine which management strategies result in desirable long-term characteristics. To classify the stability of a flow-kick equilibrium, we classify the linearization of the time-τ map given by the time-τ map of the variational equation about the equilibrium trajectory. Since the variational equation is a non-autonomous linear differential equation, we conjecture that the asymptotic stability classification of each instantaneous local linearization along the equilibrium trajectory indicates the stability of the variational time-τ map. In Chapter 3, we prove this conjecture holds when all of the asymptotic and transient behavior of the instantaneous local linearizations is the same. To explore whether the conjecture holds in general, we ask: To what degree can transient behavior differ from asymptotic behavior? Under what conditions can this transient behavior accumulate asymptotically? In Chapter 4, we develop the radial and tangential velocity framework to characterize transient behavior in autonomous linear systems. In Chapter 5, we use this framework to construct an example of a non-autonomous linear system whose time-τ map has asymptotic behavior that differs from the asymptotic behavior of each instantaneous linear system that composes it. Future work seeks to determine whether this constructed example can arise as a variational equation, and thus provide a counterexample for our conjecture.
Four Artists
Date: 1982-01-01
Access: Open access
- Bowdoin College Museum of Art exhibition catalogue from January 22-March 7, 1982.
Baroque Paintings from the Collection of Walter P. Chrysler, Jr.
Date: 1963-01-01
Access: Open access
- This catalogue is in lieu of Bulletin vol. II: no. 3.