Showing 291 - 300 of 2039 Items
Interview with Saira Toppin (Class of 2009) by Nate DeMoranville
Date: 2019-11-09
Creator: Saira Toppin
Access: Open access
- Saira Toppin ’09 discusses her upbringing in Brooklyn, New York, and how that made for a challenging transition to Brunswick, Maine. She shares how a few juniors mentored her during her first year, which helped Toppin adjust to Bowdoin. She credits this mentorship with encouraging her to carve out space for herself on campus as an Afro-Latina and also to look out for others once she became an upperclassman. She shares stories from her time on the boards of both the African American Society and the Latin American Students Organization (LASO). As co-president of LASO during her junior and senior year, Toppin helped the organization have an impact on campus by organizing Latin American Heritage Month event Fall. She made sure to mentor underclassman so that they could run the club in her absence and considers LASO to be her legacy.
The role of behavioral diversity in determining the extent to which the cardiac ganglion is modulated in three species of crab
Date: 2020-01-01
Creator: Grace Bukowski-Thall
Access: Open access
- Central pattern generators (CPGs) are neural networks that generate the rhythmic outputs that control behaviors such as locomotion, respiration, and chewing. The stomatogastric nervous system (STNS), which contains the CPGs that control foregut movement, and the cardiac ganglion (CG), which is a CPG that controls heartbeat, are two commonly studied systems in decapod crustaceans. Neuromodulators are locally or hormonally released neuropeptides and amines that change the output patterns of CPGs like the STNS and CG to allow behavioral flexibility. We have hypothesized that neuromodulation provides a substrate for the evolution of behavioral flexibility, and as a result, systems exhibiting more behavioral flexibility are modulated to a greater degree. To examine this hypothesis, we evaluated the extent to which the STNS and the CG are modulated in the majoid crab species Chionoecetes opilio, Libinia emarginata, and Pugettia producta. C. opilio and L. emarginata are opportunistic feeders, whereas P. producta has a highly specialized kelp diet. We predicted that opportunistic feeding crabs that chew and process a wide variety of food types would exhibit greater STNS neuromodulatory capacity than those with a specialized diet. The STNS of L. emarginata and C. opilio responded to the seven endogenous neuromodulators oxotremorine, dopamine, CabTrp Ia, CCAP, myosuppressin, proctolin, and RPCH, whereas the STNS of P. producta only responded to proctolin, oxotremorine, myosuppressin, RPCH (25% of the time), variably to dopamine, and not at all to CabTrp and CCAP. Because P. producta, L. emarginata, and C. opilio all belong to the Majoidea superfamily, their primary distinctions are their feeding habits. For this reason, we further predicted that there would be no relationship between diet and modulatory capacity in the cardiac ganglion (CG) of the neurogenic heart. This would suggest that a lack of STNS modulatory capacity in P. producta relative to L. emarginata and C. opilio is specific to evolved foregut function. Whole-heart recordings from P. producta indicated that, unlike the STNS, the CG responds to CabTrp and CCAP. P. producta hearts also responded to oxotremorine and inconsistently to dopamine and proctolin. The CG of C. opilio was modulated by CabTrp, CCAP, dopamine, proctolin, myosuppressin, and oxotremorine, but not RPCH. The CG of L. emarginata responded to CCAP, and inconsistently to CabTrp, dopamine, and proctolin, but not to myosuppressin, RPCH, and surprisingly oxotremorine. Although cardiac responses were not identical between species, opportunistic and specialist feeders responded more similarly to the modulators tested in the heart than in the STNS. Notably, P. producta responded to each modulator in a similar manner to C. opilio and/or L. emarginata. However, L. emarginata’s surprising lack of cardiac response to oxotremorine suggests that phylogenetic closeness may not control for differences in CG and STNS function between species. Nevertheless, sample sizes of all three species were quite small, and individual differences lead to inconsistencies in the data. As a result, sample size must be enlarged to draw firm conclusions.
“I felt so untrustworthy of my ability to get pregnant”: Women’s Embodied Uncertainties and Decisions to Become Pregnant
Date: 2020-01-01
Creator: Theodora K. Hurley
Access: Open access
- This paper identifies “embodied uncertainties”—possibilities of aging and infertility lodged within the body—as informing women’s conceptualizations of their reproductive bodies and their decisions about and approaches to getting pregnant. Using data from semi-structured interviews with a small sample of highly educated, professional, white women who had given birth within 18 months prior, this paper argues that (bio)medicalized risk discourses and neoliberal logics of responsible choice-making lodge uncertainty and the possibility of failure within women’s reproductive bodies. As they attempt to reconcile childbearing with professional and financial constraints, women may identify their bodies as laden with embodied uncertainties and may subsequently adopt strategies for becoming pregnant that seek to mitigate those embodied uncertainties, such as by trying to conceive before feeling completely ready for a pregnancy. Ultimately, (bio)medicalization and neoliberalism have transformed reproductive aging and infertility into individualized concerns and foreclosed recognition of the institutional failures that create conflicts of aging, careers, and childbearing in women’s lives.
The Soviet and American Wars in Afghanistan: Applying Clausewitzian Concepts to Modern Military Failure
Date: 2020-01-01
Creator: Artur Kalandarov
Access: Open access
- This paper evaluates the validity of three concepts from Carl von Clausewitz’s On War as they relate to contemporary military conflict. Utilizing the Soviet and American Wars in Afghanistan as case studies, the paper also offers a model for comparative conflict analysis by expanding upon Clausewitz’s culminating point concept. It argues that – despite limitations to Clausewitz’s theory of war – his concepts of culminating points in military operations, mass and concentration, and changing war aims provide useful insights into counterinsurgency military failures. Chapter One identifies the Soviet and American culminating points. Concluding that the concept of a culminating point is not applicable to the means and objectives of insurgents, it expands upon Clausewitzian theory by presenting an effectual substitute: the Counterinsurgent Acceptance Point. This is the author’s idea, and it is defined as the moment at which the counterinsurgents first publicly call for negotiations with the enemy. As the first public acknowledgment that the insurgents have denied the counterinsurgents a strictly military resolution to the conflict, it marks a crucial shift in the political framework of the war and is a fitting antithesis to the culminating point. Chapters Two and Three show how an inadequate troop presence and unclear war aims harmed Soviet and American efforts in Afghanistan. The development of insurgencies in both wars are studied to pinpoint when both country’s leaderships failed to adopt a Clausewitzian view of war, despite calls to do so by General Colin Powell in 2001 and Marshal Nikolai Ogarkov in 1979.
Spatially variable syn- and post-orogenic exhumation of the Appalachian Mountains from apatite and zircon (U-Th)/He thermochronology
Date: 2020-01-01
Creator: Luke Coughtry Basler
Access: Open access
- We present zircon and apatite (U-Th)/He (ZHe, closure temperature = 150-200ºC; AHe, closure temperature = 45-80ºC) results from two study regions in the Appalachians Mountains to investigate the timing, rates, and spatial trends of exhumation during Alleghanian orogenesis, Atlantic rifting, and post-rift passive margin conditions. Within West Virginia and Virginia, 10 ZHe dates along an across-orogen transect display an eastward younging trend, from ~425 million years (Ma) in the western Appalachian Plateau province, to ~250-300 Ma in the central Valley-Ridge fold-thrust belt, and 163 ± 29 Ma in the eastern Piedmont. Inverse thermal modeling of ZHe data using external geologic constraints indicates: (1) Pre-depositional cooling signatures within Pennsylvanian Appalachian Plateau rocks, suggesting provenance from recycled Taconic or Acadian basin strata, (2) Rapid Alleghanian (250-300 Ma) cooling in the Valley and Ridge province, indicating syn-orogenic uplift and exhumation, followed by a protracted period of stable syn-rift thermal conditions from ~250-150 Ma, and (3) Rapid rift-induced cooling in the Piedmont province, likely caused by rift-flank uplift and the post-rift lessening of the geothermal gradient. Within the Northern Appalachians of Vermont, four metamorphic samples yield averaged AHe dates of 100-120 Ma. Inverse thermal modeling indicates stable thermal conditions from 90 Ma to the present, limiting cooling driven by the recently recognized Northern Appalachian lithospheric thermal anomaly to < 20ºC. Modeling also indicates steady mid-Cretaceous (120-90 Ma) cooling (70 to 30ºC) coeval with passage over the Great Meteor Hotspot, although cooling rates are slower than would be expected during hotspot-induced thermal doming.
Active and Passive Spatial Learning and Memory in Human Navigation
Date: 2019-01-01
Creator: Caroline Rice
Access: Open access
- Previous studies show that active exploration of an environment contributes to spatial learning more than passive visual exposure (Chrastil & Warren, 2013; Chrastil & Warren, 2015). Active navigation and cognitive decision-making in a novel environment leads to increased spatial knowledge and memory of location compared to a passive exploration that removes the decision-making component. There is evidence of theta oscillations present in electroencephalography (EEG) recordings from the hippocampus and pre-frontal cortex (PFC). These low-frequency waves could reflect spatial navigation and memory performance, suggested by their involvement in communication between the formerly named brain regions. Through communication with the hippocampus, theta oscillations could be involved in the integration of new spatial information into memory. While undergoing EEG, subjects in this study either actively or passively explored a virtual maze, identified as the “Free” or “Guided” groups, respectively. After exploring, subjects’ spatial memory of the maze was tested through a task that required navigation from a starting object to a target object. Behavioral data show increased spatial memory for the Free group, indicated by significantly greater navigation to the correct target object in the memory task. EEG results indicate significantly greater theta oscillations in frontal regions for the Free group during the exploration phase. These results support those found in previous studies and could indicate a correlation between frontal theta oscillations during learning of novel environments and spatial memory.
Beyond Urban Bias: Peasant Movements and the State in Africa
Date: 2019-05-01
Creator: Connor Rockett
Access: Open access
- Focusing on sub-Saharan Africa, this study tests the hypothesis that state intervention in agrarian economies causes peasant movements to engage in broad-based contention, on regional and national levels. The study traces the connections between government land and agricultural institutions and the characteristics of rural movements that make claims on them. Case studies of regions of Tanzania, Senegal, Côte d’Ivoire, and Ethiopia show the ways in which rural movements are constructed in response to the political and social environments in which they arise. That is, the comparisons demonstrate that the character of political authority and social organization are important determinants of the form taken by peasant movements.
Effects of octopamine and tyramine on the cardiac system of the lobster, Homarus americanus
Date: 2019-05-01
Creator: Casey Breslow
Access: Open access
- Modulation in neural systems is important for regulating physiology and behavior (Wright et al., 2010). Peptides, hormones, and amines are common neural modulators, acting on many neural systems across species. One group of neural networks that can be regulated are central pattern generators (CPGs), which generate rhythmic neural patterns, which drive behaviors (Marder and Bucher, 2001). Octopamine, and its precursor tyramine, are two amines that have been found to regulate (CPGs) across species (Cooke, 2002; Fussnecker et al., 2006). One role of octopamine in the decapod neurogenic heart is regulating the frequency and the duration of heart beats. However, the precise site of octopamine modulation within the cardiac system is not yet known (Kurumoto and Ebara, 1991). One possible site of action is the cardiac ganglion (CG), the CPG in decapod hearts. The transcripts for the enzymes required to synthesize octopamine from tyramine have been identified and localized in the CG (Christie et al., 2018). This would suggest that octopamine is produced in the CG, where it could have a direct action on those neurons, or it could be released peripherally. We have found individual variation in the response to octopamine and its precursor tyramine, and significant effects of frequency and contraction amplitude in the whole heart.
Midterm Decline in Comparative Perspective
Date: 2019-05-01
Creator: Duncan Gans
Access: Open access
Traders and Troublemakers: Sovereignty in Southern Morocco at the End of the 19th Century
Date: 2020-01-01
Creator: Joseph Campbell Hilleary
Access: Open access
- This thesis explores changes in and challenges to Moroccan political authority in the region of the Sous during the late nineteenth century. It attempts to show how the phenomenon of British informal empire created a crisis over Moroccan sovereignty that caused the sultan to both materially and discursively change the way he wielded power in southern Morocco. It further connects these changes and the narrative contestation that accompanied them to the construction of the Bilad al-Siba/Bilad al-Makhzan dichotomy found in Western academic literature on Morocco starting in the colonial period. It begins with an examination of letters between Sultan Hassan I and local leaders in the Sous that show a shift toward a more bureaucratic form of governance in response to repeated openings of black-market ports by British trading companies. It then investigates the textual debate over the framing of Hassan I’s military expeditions to southern Morocco in the 1880s and 90s by drawing on a collection of European travel accounts, American consular reports, and a royal Moroccan history. Finally, it ties the illegal trade in the Sous to the broader theory of informal empire through a close examination of the Tourmaline Incident of 1897, using documents from the British Foreign Office as well as published accounts by crew members aboard the Tourmaline, itself.