Showing 251 - 260 of 583 Items
A Bayesian hierarchical mixture model with continuous-time Markov chains to capture bumblebee foraging behavior
Date: 2021-01-01
Creator: Max Thrush Hukill
Access: Open access
- The standard statistical methodology for analyzing complex case-control studies in ethology is often limited by approaches that force researchers to model distinct aspects of biological processes in a piecemeal, disjointed fashion. By developing a hierarchical Bayesian model, this work demonstrates that statistical inference in this context can be done using a single coherent framework. To do this, we construct a continuous-time Markov chain (CTMC) to model bumblebee foraging behavior. To connect the experimental design with the CTMC, we employ a mixture model controlled by a logistic regression on the two-factor design matrix. We then show how to infer these model parameters from experimental data using Markov chain Monte Carlo and interpret the results from a motivating experiment.
Cascades and Overexposure in Networks Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2021-01-01
Creator: Kim Hancock
Access: Access restricted to the Bowdoin Community
Characterizing and Investigating the Electrophysiological Properties of the Plastic Cricket Auditory System in Response to Cooling
Date: 2022-01-01
Creator: Hannah Tess Scotch
Access: Open access
- The auditory system of the Mediterranean field cricket (Gryllus bimaculatus) is capable of profound compensatory plasticity. Following deafferentation due to the loss of an auditory organ, the dendrites of intermediate auditory neuron Ascending Neuron 2 (AN-2) grow across the midline and functionally connect to contralateral afferents. The loss of the auditory organ can be mimicked with reversible cold-deactivation, in which cooled Peltier elements silence the auditory organ and its afferents. Though this would presumably prevent AN-2 from firing, cooling instead induces a novel firing pattern called DOPE (delayed-onset, prolonged-excitation). In this study, intracellular physiological recordings were completed before, during, and after cooling in response to “chirp” and “pulse” sounds. Analysis was performed within and across crickets to characterize DOPE. Results revealed expected variability across individuals, as well as a wider spread of onset delay and a decrease in spike frequency and number of spikes per burst relative to baseline within individuals during cooling. Generally, subsequent warming only partially restored the neuronal responses to baseline as measured by all three parameters. This was particularly true in response to “pulse” stimuli. Future experiments will investigate if DOPE is caused by synaptic inputs or intrinsic properties of AN-2, as well as the role of inhibition in the circuit. Eventually, we hope to develop a complete model of the auditory circuit for future investigations of plasticity, with ramifications for treating human neuronal injury.
Characterizing the Motor Activity Patterns of the Mammalian Thoracic Spinal Cord Neural Network This record is embargoed.
- Embargo End Date: 2027-05-16
Date: 2024-01-01
Creator: Sam McClelland
Access: Embargoed
A histological investigation of Arceuthobium pusillum infections in Picea rubens and Picea glauca
Date: 2024-01-01
Creator: Sade K. McClean
Access: Open access
- Arceuthobium pusillum is a hemiparasite that infects select Picea species. The hosts of A. pusillum do not experience the same symptoms of infection. A. pusillum infections are more fatal to P. marinara, and P. glauca. P. rubens, on the other hand, can survive longer with sustained infection. This presents itself as a contemporary issue because P. glauca, one of the parasite’s most vulnerable hosts, was untethered from ecological competition when old growth forests were subjected to large scale anthropogenic disturbances. These disturbances allowed P. glauca to proliferate, with A. pusillum following. A deeper understanding of the host-species specific responses to A. pusillum infection can broaden general knowledge of parasitic growth and development while also potentially inspiring conservation techniques. This study took advantage of the intrinsic differences between host and parasite to visualize infections in P. rubens and P. glauca, highlighting differences in infection outcome. By illuminating lignin and callose within cross sections of infected P. rubens and P. glauca branches, it was revealed that P. rubens forms dense bands of cells around the cortical strands of infection. These bands form more frequently in P. rubens than in P. glauca and are of a significantly larger area in P. rubens than in P. glauca (t(8), p=0.003, p=0.005). The discovery of the exterior bands is novel and exciting, as the bands are possibly made of callose and potentially facilitate P. rubens survival against A. pusillum infection. The foundational discoveries and results of this study should inspire, and warrant, further analysis.
Are People Blaming Artificial Intelligence More or Less for Incorrect Advice? Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2029-06-01
Date: 2024-01-01
Creator: Anh Nguyen
Access: Access restricted to the Bowdoin Community
Creating Enantioselective Peptoid Catalysts with 2-Picolylamine and 2-Picolinic Acid Catalytic Sites Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2024-01-01
Creator: Devin Kathleen O’Loughlin
Access: Access restricted to the Bowdoin Community
Bamboo Corals as Climate Archives: Radiocarbon-based Chronologies and Evaluation of Mg/Li as a Temperature Proxy Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2016-05-01
Creator: Megan M Freiberger
Access: Access restricted to the Bowdoin Community
Physiological responses of the American lobster cardiovascular system to neuropeptide SGRNFLRFamide (SGRN)
Date: 2024-01-01
Creator: Andre Eden
Access: Open access
- During every second of a human’s life, the cardiovascular system is modulated by factors both intrinsic and extrinsic to the physiology of the heart. We can uncover new insights regarding the nature of our system through investigations of similar systems in other model species. One example materializes itself in the form of the American Lobster (Homarus americanus) whose single-chambered heart finds resemblance to the function and anatomy to that of humans. The lobster heart is powered by the cardiac ganglion (CG), a group of neurons that drive contractions of surrounding heart muscles, known as the myocardium. Both the CG and myocardium work in a feedback loop, with both intrinsic (afterload and preload) and extrinsic (temperature and neuropeptides) factors affecting cardiac output (CO) or the overall ability of the heart to carry out its primary function of nutrient distribution. In this paper, we examine how the addition of these factors into in vitro whole heart preparations affect CO and other associated variables. From experimentation, we conclude that the neuropeptide SGRNFLRFamide (SGRN) increases the heartbeat frequency and the active force exerted by the heart. We also conclude that increases in temperature decrease CO as higher temperatures decrease heartbeat frequency and the active force exerted by the heart. Lastly, we conclude that the effect of preload and afterload combined produce more robust effects on the CO and active force of the heart, potentially painting a better picture of what may happen in vivo.
Mitigation of Negative Effects of Ocean Change on Oysters by Eelgrass and its Implications for Aquaculture in Midcoast Maine
Date: 2022-01-01
Creator: Fiona G Ralph
Access: Open access
- Species interactions are important to organisms and to the ecosystems they inhabit. These interactions, sometimes facilitations, can result in increased resiliency for both species. When facilitation occurs, organisms co-assist with physiological and environmental stressors. As anthropogenic impacts become more stressful for modern organisms, these interactions could offer a solution for many species. Ocean acidification has been shown to be detrimental to many calcifying organisms including oysters. More acidic conditions can slow the process of shell calcification, which can slow growth rates. This effect could directly impact the robust oyster farming business in Midcoast Maine. Because of its possible importance to oyster crops, we assessed the potential of Zostera marina, or eelgrass, to ameliorate the stresses of ocean acidification on farmed Eastern Oysters (Crassotrea virginica). Photosynthesizing organisms such as seagrasses have been shown to locally raise pH, which could create growth refugia for calcifying organisms. While eelgrass has the potential to enhance oyster growth rates, its meadows could also be influencing food availability. To better understand these dynamics, we grew C. virginica in two locations in Harpswell, ME. Crassostrea virginica were split into three habitats at each location: seagrass, fringe, and mudflat, and placed on surface or benthic arrays. We found that seagrass presence and depth interacted to increase shell growth rate. Similarly, Z. marina improved condition index of C. virginica. As ocean acidification worsens, oyster farmers might have to turn to mitigation strategies to ensure profit yield from their labors. Zostera marina could be the solution to their future problems.