Honors Projects
Showing 101 - 110 of 298 Items
N,N’-Dimethyimidazolium-2-Carboxylate as a Ligand Precursor for the Accession of a Constrained Olefin Dimerization Catalyst
Date: 2020-01-01
Creator: Michael Harris
Access: Open access
- A significant market share of modern plastics is held by long-chain hydrocarbon polymers, such as polyethylene and polypropylene, properties of which can be dramatically changed by addition of linear α-olefins. Production of linear α-olefins involves the creation of many unwanted byproducts, representing significant quantities of both economic and ecological waste. While catalysts have been designed to selectively produce industrially useful olefins, these catalysts often encounter challenges such as synthesis of other unwanted byproducts, slow reaction times, and difficulty of synthesis. Based on one such prior catalyst, we report here synthetic work towards a cobalt catalyst with a constrained N-heterocyclic carbene supporting ligand predicted to allow for more favorable product distributions. Synthesis of two precursors to a sterically unhindered N-heterocyclic carbene, as well as development of a synthetic protocol for the coordination of N,N’- dimethylimidazolium-2-carboxylate to Cp*Co(ethene)2 was completed. Activation of the precatalyst and preliminary catalytic experiments were performed, though abbreviated research periods made complete analysis impossible. Finally, we report evidence of the formation of a novel cobalt-NHC dimer as a temperature controlled byproduct of the desired catalyst synthesis.
Alongside Despair: Signs of Life on the River des Peres
Date: 2020-01-01
Creator: Marina Henke
Access: Open access
- This River des Peres is a partially enclosed river which runs through St. Louis, Missouri. Used since prior to the city’s founding, the des Peres has gone through two considerable engineering projects: one in 1901 in light of the World’s Fair, and one in 1923, which encapsulated more than half of the river and placed nearly five miles of it underground. Presently, the des Peres constitutes the backbone of the sanitary and sewer system of St. Louis city and county. Ultimately, the river offers a broad meditation on what it means to live around and in a “natural” waterway that is simultaneously not natural at all. Themes of St. Louis are equally reflected in the river: of environmental racism, of Midwestern decline, and of urban decay and renewal. Additionally, those who interact with the river prove a broad cast of characters. Through using a selection of interviews with locals, alongside an engagement with the work of contemporary poet Donald Finkel, this piece of creative nonfiction explores the multiplicity, and ultimately the value, of distorted natural spaces.
Mechanisms underlying variable responses to the neuropeptide C-type allatostatin (AST-C) across isoforms and among individuals in the American lobster, Homarus americanus
Date: 2020-01-01
Creator: Audrey J. Muscato
Access: Open access
- Central pattern generators (CPGs) produce patterned outputs independent of sensory input. The cardiac neuromuscular system of the American lobster (Homarus americanus) is driven by a CPG called the cardiac ganglion (CG), which is composed of nine neurons, making it a model system of study. Modulation of CPGs allows for functional flexibility. One neuropeptide family that modulates the CG is C-type allatostatin (AST-C I-III). Previous research has shown variation in the responses of the CG across the three isoforms and among individuals. First, we investigated why AST-C I and III elicit responses that are more similar to each other than they are to the responses elicited by AST-C II. We hypothesized that an amino acid difference in the conserved sequence was responsible for the observed variation in responses. We synthesized isoforms of AST-C that replaced the endogenous amino acid and recorded responses to these isoforms. The identity of one particular amino acid in the conserved sequence seems to be responsible for variations in responses in frequency. Next, we focused on variation among individuals in their responses to AST-C I and III. We hypothesized that the mechanism behind this individual variation is differential expression of AST-C receptors and/or their downstream targets. We recorded physiological responses of the cardiac system to AST-C and then sequenced CG RNA from the same lobsters. Differential expression of one of the AST-C receptors and a number of downstream factors is correlated with physiological response. These findings inspire further experimentation investigating molt cycle as the underlying cause.
A Stepping-Stone? An Analysis of How the Minimum Wage Impacts the Wage Growth of Individuals in Monopsonistic Industries
Date: 2022-01-01
Creator: Levi McAtee
Access: Open access
- Do minimum wage increases serve as stepping-stones to higher-paying jobs for low-pay workers? This paper analyzes the impact of state minimum wage policy on the one-year wage growth rates of individuals across the wage distribution and whether that impact changes for individuals in highly monopsonistic industries. I review the recent literature on the disemployment effect, the impact of the minimum wage on wage growth rates, the nature of monopsonistic industries, and the relationship between the minimum wage and monopsony power. I offer theoretical reasons why the minimum wage may impact the wage growth rates of individuals in monopsonistic industries differently than it impacts those of individuals in competitive industries. I then re-estimate Lopresti’s and Mumford’s (2016) panel fixed effects model to determine how the effect of a minimum wage increase depends nonlinearly on the size of the increase. Using data from 2005-2008, Lopresti and Mumford found that small minimum wage increases have a significant negative impact on wage growth rates, while large minimum wage increases have a significant positive impact. Using data from 2016-2019, I find similar results. As my primary empirical contribution, I test whether individuals in highly monopsonistic industries experience minimum wage changes differently than individuals in more competitive industries. I find monopsony power in the form of high labor immobility primarily impacts the wage growth rates of high-pay workers and does not influence how low-pay workers experience minimum wage changes. Finally, I recommend policymakers impose larger minimum wage increases to avoid impeding the wage-growth of low-pay workers.
The Structure and Unitary Representations of SU(2,1)
Date: 2015-05-01
Creator: Andrew J Pryhuber
Access: Open access
Antimicrobial Peptides (AMPs) in the Lobster, Homarus Americanus: Isolation and Activity
Date: 2021-01-01
Creator: Ruby Chimereucheya Ahaiwe
Access: Open access
- The American lobster Homarus americanus uses its innate immune system for protection against foreign bodies and diseases. Hemocytes in the innate immune system are responsible for the rapid and effective cellular response against pathogens and infections observed in lobsters. These hemocytes, particularly semi-granulocytes and granulocytes, store antimicrobial peptides (AMPs) which specifically target and destroy microbes. Hemocyte samples from the American lobster Homarus americanus hemolymph or circulatory fluid, mixed and fractionated into separated semi-granular and granular cell samples, were analyzed for possible AMP presence. A defensin AMP, Hoa-D1, (SYVRSCSSNGGDCVYRCYGNIINGACSGSRVCCRSGGGYamide; with C representing a cysteine participating in a disulfide bond) was successfully isolated and identified by mass using reversed-phase high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS/MS). Preliminary results also show the defensin AMP to be concentrated in the semi-granulocytes and granulocytes.Hoa-D1 was isolated via HPLC fractionation. Isolated Hoa-D1 and semi-granular and granular hemocyte extracts were tested for bioactivity against the gram-negative bacteria, Escherichia coli, using the Kirby-Bauer disk diffusion assay. The assay did not show any activity, an outcome attributed to concentrations of the AMP that were too low to have any antimicrobial effect on E. coli. Subsequent work on this study should involve increasing the concentration of Hoa-D1 in test samples. Studying function of AMPs in the American lobster can provide more information on the depth of their cellular immune responses in other crustaceans, and possibly contribute to the development of novel antibiotics for treating diseases in humans.
Assigning Legal Punishment: Individual Differences in Justice Sensitivity and Selective Attention
Date: 2015-05-01
Creator: Emily C. Weinberger
Access: Open access
- Selective attention and justice sensitivity (JS), a personality trait reflecting individual differences in perceptions of injustice, have been shown to affect how people assign punishments. In the present study peoples’ decision-making processes were investigated to better understand the inconsistencies in legal punishment decisions, particularly when using retributive versus restorative justice. Subjects participated in three phases of the experiment. First, subjects completed a justice sensitivity scale and then rated the appropriateness of punishment options to handle a criminal scenario. Second, participants’ selective attention was indicated by their recall of pertinent features from three ambiguous criminal scenarios. Finally, participants were primed with either restorative justice or neutral control words, and rated the appropriateness of punishment options to handle a new criminal scenario. Results revealed no significant associations between JS and ratings of punishment options, although patterns suggested negative relationships between observer JS and retributive justice ratings, and victim JS and restorative justice ratings. Results did show a significant effect of JS in predicting the facts remembered, such that as observer JS increased, more restorative justice facts were recalled, and as victim JS increased, fewer restorative justice facts were recalled. No significant effect of the restorative justice prime was observed. These results may contribute to better understanding of criminal justice policy in the United States.
Sensitivity Analysis of Basins of Attraction for Gradient-Based Optimization Methods
Date: 2022-01-01
Creator: Gillian King
Access: Open access
- This project is an analysis of the effectiveness of five distinct optimization methods in their ability in producing clear images of the basins of attraction, which is the set of initial points that approach the same minimum for a given function. Basin images are similar to contour plots, except that they depict the distinct regions of points--in unique colors--that approach the same minimum. Though distinct in goal, contour plots are useful to basin research in that idealized basin images can be inferred from the steepness levels and location of extrema they depict. Effectiveness of the method changes slightly depending on the function, but is generally defined as how closely the basin image models contour information on where the true minima are located, and by the clarity of the resulting image in depicting well-defined regions. The methods are tested on four distinct functions which were chosen to assess how each method performs in the presence of various challenges. This project ranks the five methods for their overall effectiveness and consistency across the four functions, and also analyzes the sensitivity of the methods when small changes are made to the function. In general, less sensitive and consistently effective methods are more applicable and reliable in applied optimization research.
The development of begging calls in Yellow Warblers
Date: 2015-05-01
Creator: Jackson F Bloch
Access: Open access
- Nestling birds use begging calls to solicit resources from adults. Efficient transmission of calls is necessary for motivating parental feeding and outcompeting siblings. However, ambient acoustic masking and costs such as predation may influence the structure of the calls. While many interspecific comparisons of begging behavior have been made, the ontogeny of calls is understudied. In this study, Yellow Warbler (Setophaga petechia) begging calls were recorded and analyzed at different stages of nestling development to document changes in acoustic structure and gain insight into the selective forces that influence call development. Begging calls increased in peak frequency, frequency range, and amplitude during the 5-day recording period. Call duration did not change with age. Call structure did not differ between nestlings living in distinct acoustic environments. As begging calls increase in amplitude with age, perhaps due to increased food needs and competition from nestmates, nestlings may compensate for increased predation risk by increasing the peak frequency of the calls. Higher frequency calls attenuate more quickly than do low frequency calls and fall outside the frequency range of maximum hearing sensitivity for some potential predators. Previous studies on warbler begging have shown that nestlings of ground-nesting warblers, which are subject to higher rates of predation, beg at higher frequencies than do nestlings of tree-nesting warblers. This study supports the hypothesis that changes to begging call structure during development mirror the differences in call structure of species under different predation risks.
Personally Relevant Indoor Nature Imagery’s Impact on Students’ Well-Being, Connection to Nature, and Eco-Conscious Behaviors
Date: 2019-05-01
Creator: Sarena Sabine
Access: Open access
- Previous research has shown that experiences in nature are predictive of increased connection to nature, well-being, and pro-environmental behavior. The current study investigated whether daily exposure to indoor nature imagery would also improve well-being and eco-conscious behaviors, and whether personally relevant images would enhance this hypothesized effect. Participants completed a test assessing baseline connection to nature and well-being, specifically satisfaction with life, positive and negative emotions, and stress. In the 2 (Nature vs. Built) X 2 (Familiar vs. Unfamiliar) study design, 125 participants either received a poster from a photo that they submitted (a personally-relevant nature scene or personally-relevant built scene) or a poster of an unfamiliar natural or built scene. After four weeks of daily exposure to this new poster in their home, participants completed a post-test which included the same measures of well-being and connection to nature, along with a novel eco-conscious behaviors measure involving environmental petitions. The nature intervention significantly improved participants’ satisfaction with life. The personal relevancy of images did not enhance well-being, either alone nor in interaction with image content. The finding that daily exposure could lead to improved well-being has implications for addressing mental health concerns.