Showing 121 - 130 of 583 Items
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.
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.
Tradition et Nouveauté: Une étude du baccalauréat et de la réforme Blanquer
Date: 2020-01-01
Creator: Fiona Carey
Access: Open access
- The baccalauréat exam has played a significant role in the lives of French high schoolers for more than two centuries. Not only does the exam determine a student’s eligibility for university, it is a long-standing national tradition and an important aspect of French identity. The baccalauréat consists of a core curriculum and a choice of specialties, all of which prepare students for the exams that they will take in their last two years of high school. In 2018, Minister of Education Jean-Michel Blanquer announced a reform to the baccalauréat that would drastically alter the content and structure of the exam. Blanquer’s reform offers students a wider variety of specialties and in doing so hopes to eliminate the supposed hierarchies which have historically valued sciences over other subject matters. This reform revolutionizes the system while simultaneously remaining deeply rooted in tradition. While Blanquer’s reform introduces changes to the core curriculum and an entirely new list of specialties, it preserves other aspects of the French education system, particularly the mandatory study of philosophy. This thesis examines the contrasting novelty and tradition of Blanquer’s baccalauréat. In order to understand the intent and implications of his reform, this thesis studies a series of historic reforms, provides a detailed explanation of Blanquer’s changes, and finally discusses a selection of anonymous survey responses concerning its potential impacts. In discussing these survey responses, I highlight three main themes: (1) hierarchies and freedom of choice, (2) collectivity and individuality, and (3) the role of nationalism in the baccalauréat.
Prendersi Cura: Taking Care of Nature in Perugia, Italy
Date: 2024-03-20
Creator: Katharine Kurtz
Access: Open access
- Cities need more green spaces to adapt to climate change and facilitate community resilience. However, successfully managing green spaces is challenging. City governments consistently employ top-down management practices that limit the benefits, usage, and perception of such spaces as Nature. Further, current management practices overlook socio-cultural factors important to residents. Using the existing categories of urban green spaces (UGS) and informal green spaces (IGS), this article situates the cultural practice prendersi cura as a way to conceptualize successful, bottom-up green space management. The term prendersi cura, meaning “to take care of” in Italian, emerged through interviews in Perugia, Italy, and reflects the socio-ecological value of IGS and the disconnect between residents and city-managed UGS. This study employed mixed methods, combining 10 weeks of participant observation, 13 interviews, and GIS analysis to understand the relationship between Perugians and their green spaces. Results indicate that interviewees did not describe city-supported UGS (i.e. top-down green spaces like parks or historic gardens) as Nature, even if they were areas of dense vegetation and recognized by the City of Perugia in GIS analyses. In contrast, interviewees described IGS (i.e. community gardens, vacant lots, or potted plants) that were unrecognized in city GIS visualizations as Nature, indicating a stronger attachment to green spaces when interviewees had active roles in their management or witnessed community-based management practices. This paper demonstrates the importance of managing green spaces through a socio-ecological framework that considers user perceptions and cultural values. To allow greening initiatives to reach their full potential, it is critical to embrace local values and participation in management practices.
They Used to Be Castles Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2021-01-01
Creator: Lily Anna Fullam
Access: Access restricted to the Bowdoin Community
From “This Revolution is Neither Communist nor Capitalist!” to “Long Live the Socialist Revolution:” The Deterioration of U.S.-Cuban Relations from 1958-1961
Date: 2023-01-01
Creator: Julia Lyne
Access: Open access
- This thesis studies the deterioration of U.S.-Cuban relations from 1958-1961. Mainly drawing from primary sources from the National Archives, it seeks to answer and understand how and why relations deteriorated so rapidly. It pushes against the common belief that U.S.-Cuban relations were doomed from the start, instead highlighting in Chapter One Fidel Castro’s rise to power (and Fulgencio Batista’s fall from power) and revealing that the U.S. government was not entirely against Castro’s seizure of power. Chapter Two explores Castro’s first year in power and the (futile) attempts made by both governments to keep relations alive. Finally, it closes with the destruction of official and unofficial relations, suggesting that President Eisenhower’s covert approval of the invasion of the Bay of Pigs marked the covert ending to political relations as well as rising economic and political tensions due to an incompatibility of demand and interest in the sugar and oil industries. Ultimately, this thesis suggests that it was not just a matter of communism that led to the destruction of U.S.-Cuban relations at the time; instead, it was because of compounding effects of other various other economic and political factors and incompatibilities, such as the sugar and oil industries, public and political slandering and attacks from both sides, and an increasing acceptance of the Soviet Union and its supporters. This analysis does not seek to argue against the influence of communism in its entirety; rather, it aims to highlight and nuance the contributing factors to this deterioration.
Properties of Slicing Conditions for Charged Black Holes
Date: 2023-01-01
Creator: Sean E. Li
Access: Open access
- We consider an earlier analysis by Baumgarte and de Oliveira (2022) of static Bona-Massó slices of stationary, nonrotating, uncharged black holes, represented by Schwarzschild spacetimes, and generalize that approach to Reissner-Nordström (RN) spacetimes, representing stationary, nonrotating black holes that carry a nonzero charge. This charge is parametrized by the charge-to-mass ratio λ ≡ Q/M, where M is the black-hole mass and the charge Q may represent electrical charge or act as a placeholder for extensions of general relativity. We use a height-function approach to construct time-independent, spherically symmetric slices that satisfy a so-called Bona-Massó slicing condition. We compute quantities such as critical points and profiles of geometric quantities for several different versions of the Bona-Massó slicing condition. In some cases we do this analytically, while in others we use numerical root-finding to solve quartic equations. We conclude that in the extremal limit as λ → 1, all slices that we consider approach a unique slice that is independent of the chosen Bona-Massó condition. We then study dynamical, i.e. time-dependent, Bona-Massó slices by analytically predicting the qualitative behavior of the central lapse, i.e. the lapse at the black-hole puncture, for a particular slice that Alcubierre (1997) proposed to mitigate gauge shocks. These shock-avoiding slices are a viable alternative to the very common so-called 1 + log slices but exhibit different behavior in dynamical simulations. We use a perturbation of the radial coordinate at the location of the puncture to recover approximately harmonic late-time oscillations of the central lapse that Baumgarte and Hilditch (2022) observed in numerical simulations.
Structural and methodological factors influencing the sorption of alkylpyridiniums to aluminosilicates Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2023-01-01
Creator: Seamus Frey
Access: Access restricted to the Bowdoin Community
The Influence of Polymers on the Solubility of Flufenamic Acid and Mefenamic Acid Cocrystals This record is embargoed.
- Embargo End Date: 2027-05-16
Date: 2024-01-01
Creator: Morgan Adams
Access: Embargoed