Showing 4901 - 4950 of 5831 Items
Date: 2020-12-01
Creator: J. Joe Hull, Melissa A. Stefanek, Patsy S. Dickinson, Andrew E. Christie
Access: Open access
- Over the past decade, many new peptide families have been identified via in silico analyses of genomic and transcriptomic datasets. While various molecular and biochemical methods have confirmed the existence of some of these new groups, others remain in silico discoveries of computationally assembled sequences only. An example of the latter are the CCRFamides, named for the predicted presence of two pairs of disulfide bonded cysteine residues and an amidated arginine-phenylalanine carboxyl-terminus in family members, which have been identified from annelid, molluscan, and arthropod genomes/transcriptomes, but for which no precursor protein-encoding cDNAs have been cloned. Using routine transcriptome mining methods, we identified four Homarus americanus (American lobster) CCRFamide transcripts that share high sequence identity across the predicted open reading frames but more limited conservation in their 5′ terminal ends, suggesting the Homarus gene undergoes alternative splicing. RT-PCR profiling using primers designed to amplify an internal fragment common to all of the transcripts revealed expression in the supraoesophageal ganglion (brain), eyestalk ganglia, and cardiac ganglion. Variant specific profiling revealed a similar profile for variant 1, eyestalk ganglia specific expression of variant 2, and an absence of variant 3 expression in the cDNAs examined. The broad distribution of CCRFamide transcript expression in the H. americanus nervous system suggests a potential role as a locally released and/or circulating neuropeptide. This is the first report of the cloning of a CCRFamide-encoding cDNA from any species, and as such, provides the first non-in silico support for the existence of this invertebrate peptide family.
Date: 1947-01-01
Access: Open access
- Bowdoin College Bulletin no. 284
Date: 1955-01-01
Access: Open access
- Bowdoin College Bulletin no. 314
Date: 2019-10-01
Creator: Patsy S. Dickinson, Heidi M. Samuel, Elizabeth A. Stemmler, Andrew E. Christie
Access: Open access
- The SIFamides are a broadly conserved arthropod peptide family characterized by the C-terminal motif –SIFamide. In decapod crustaceans, two isoforms of SIFamide are known, GYRKPPFNGSIFamide (Gly1-SIFamide), which is nearly ubiquitously conserved in the order, and VYRKPPFNGSIFamide (Val1-SIFamide), known only from members of the astacidean genus Homarus. While much work has focused on the identification of SIFamide isoforms in decapods, there are few direct demonstrations of physiological function for members of the peptide family in this taxon. Here, we assessed the effects of Gly1- and Val1-SIFamide on the cardiac neuromuscular system of two closely related species of Cancer crab, Cancer borealis and Cancer irroratus. In each species, both peptides were cardioactive, with identical, dose-dependent effects elicited by both isoforms in a given species. Threshold concentrations for bioactivity are in the range typically associated with hormonal delivery, i.e., 10−9 to 10−8 M. Interestingly, and quite surprisingly, while the predicted effects of SIFamide on cardiac output are similar in both C. borealis and C. irroratus, frequency effects predominate in C. borealis, while amplitude effects predominate in C. irroratus. These findings suggest that, while SIFamide is likely to increase cardiac output in both crabs, the mechanism through which this is achieved is different in the two species. Immunohistochemical/mass spectrometric data suggest that SIFamide is delivered to the heart hormonally rather than locally, with the source of hormonal release being midgut epithelial endocrine cells in both Cancer species. If so, midgut-derived SIFamide may function as a regulator of cardiac output during the process of digestion.
Date: 2023-08-09
Creator: Douglas Chapman
Access: Open access
- This statement was given privately.
Date: 1941-01-01
Access: Open access
- Bowdoin College Bulletin no. 255
Date: 2020-01-01
Creator: John Sweeney
Access: Open access
- Jean-Jacques Rousseau and Alexis de Tocqueville each warn that the dominant cultures of their days may hinder the project of self-government. Against the backdrop of advancing Enlightenment philosophy, Rousseau writes that as social visibility increases relative to intimate connection, the drive for recognition corrupts self-love. Following the American and French revolutions, Tocqueville explores the democratic erosion of social hierarchies. He writes that a rise in individualism may obscure “self-interest well-understood”—the perspective gained through collaboration with others, thoughtful reflection, and reverence for truths that lie beyond the dictates of cursory instincts. In this project, I apply these political theories to the Digital Age. I explain how the distinction between the physical world and the digital realm has actualized Rousseau’s depiction of double men, “always appearing to relate everything to others and never relating anything except to themselves alone.” In the era of social distancing, technological evolution threatens to induce regression in the sociability and reflective agency that promote our capacity for self-government. Accordingly, I argue that Rousseau’s theory of corrupted drive for recognition and Tocqueville’s theory of individualism inform a new danger to political freedom: digital tribalism.
Date: 2020-12-01
Creator: Andrew E. Christie, Cindy D. Rivera, Catherine M. Call, Patsy S. Dickinson, Elizabeth A., Stemmler, J. Joe Hull
Access: Open access
- Over the past decade, in silico genome and transcriptome mining has led to the identification of many new crustacean peptide families, including the agatoxin-like peptides (ALPs), a group named for their structural similarity to agatoxin, a spider venom component. Here, analysis of publicly accessible transcriptomes was used to expand our understanding of crustacean ALPs. Specifically, transcriptome mining was used to investigate the phylogenetic/structural conservation, tissue localization, and putative functions of ALPs in decapod species. Transcripts encoding putative ALP precursors were identified from one or more members of the Penaeoidea (penaeid shrimp), Sergestoidea (sergestid shrimps), Caridea (caridean shrimp), Astacidea (clawed lobsters and freshwater crayfish), Achelata (spiny/slipper lobsters), and Brachyura (true crabs), suggesting a broad, and perhaps ubiquitous, conservation of ALPs in decapods. Comparison of the predicted mature structures of decapod ALPs revealed high levels of amino acid conservation, including eight identically conserved cysteine residues that presumably allow for the formation of four identically positioned disulfide bridges. All decapod ALPs are predicted to have amidated carboxyl-terminals. Two isoforms of ALP appear to be present in most decapod species, one 44 amino acids long and the other 42 amino acids in length, both likely generated by alternative splicing of a single gene. In carideans, a gene or terminal exon duplication appears to have occurred, with alternative splicing producing four ALPs, two 44 and two 42 amino acid isoforms. The identification of ALP precursor-encoding transcripts in nervous system-specific transcriptomes (e.g., Homarus americanus brain, eyestalk ganglia, and cardiac ganglion assemblies, finding confirmed using RT-PCR) suggests that members of this peptide family may serve as locally-released and/or hormonally-delivered neuromodulators in decapods. Their detection in testis- and hepatopancreas-specific transcriptomes suggests that members of the ALP family may also play roles in male reproduction and innate immunity/detoxification.
Date: 2020-06-01
Creator: Andrew E. Christie, J. Joe Hull, Patsy S. Dickinson
Access: Open access
- Gap junctions are physical channels that connect adjacent cells, permitting the flow of small molecules/ions between the cytoplasms of the coupled units. Innexin/innexin-like proteins are responsible for the formation of invertebrate gap junctions. Within the nervous system, gap junctions often function as electrical synapses, providing a means for coordinating activity among electrically coupled neurons. While some gap junctions allow the bidirectional flow of small molecules/ions between coupled cells, others permit flow in one direction only or preferentially. The complement of innexins present in a gap junction determines its specific properties. Thus, understanding innexin diversity is key for understanding the full potential of electrical coupling in a species/system. The decapod crustacean cardiac ganglion (CG), which controls cardiac muscle contractions, is a simple pattern-generating neural network with extensive electrical coupling among its circuit elements. In the lobster, Homarus americanus, prior work suggested that the adult neuronal innexin complement consists of six innexins (Homam-Inx1-4 and Homam-Inx6-7). Here, using a H. americanus CG-specific transcriptome, we explored innexin complement in this portion of the lobster nervous system. With the exception of Homam-Inx4, all of the previously described innexins appear to be expressed in the H. americanus CG. In addition, transcripts encoding seven novel putative innexins (Homam-Inx8-14) were identified, four (Homam-Inx8-11) having multiple splice variants, e.g., six for Homam-Inx8. Collectively, these data indicate that the innexin complement of the lobster nervous system in general, and the CG specifically, is likely significantly greater than previously reported, suggesting the possibility of expanded gap junction diversity and function in H. americanus.
Date: 2021-01-01
Creator: Andrew Close Bolender
Access: Open access
- Plant cell adhesion is mediated by the extracellular matrix (ECM) or cell wall and plays an important role in plant morphogenesis and development. The amount, modification, and cleavage of pectin in the cell wall are major contributors to the adhesive properties of the ECM. To gain a more complete picture of plant cell adhesion processes, Arabidopsis thaliana seedlings were previously mutagenized and screened for hypocotyl adhesion defects. Genomic sequencing of one plant exhibiting an adhesion defect, isolate 242, showed that two mutations, one in cellulose synthase (CesA1) and another in a sugar transporter, are candidates for the causative mutation. This thesis reports that CesA1 is necessary for proper plant cell adhesion, while the sugar transporter encoded at At4g32390 is not. Dark grown seedlings homozygous for mutations in CesA1 stain in ruthenium red, indicating atypical adhesion, while those homozygous for null mutations in At4g32390 do not. Previous study of another adhesion mutant revealed ELMO1, a Golgi protein necessary for plant cell adhesion, and four additional homologs ELMO2-5 in the A. thaliana genome. Two of these homologs, ELMO2 and ELMO3, fused to GFP, colocalized with mCherry-MEM1 markers in the Golgi, but not mCherry-NLM12 ER markers, indicating that ELMO2 and ELMO3 are also Golgi proteins.
Date: 2021-01-01
Creator: Mitchel Jurasek
Access: Open access
- Through the analysis of two contemporary conversion therapy novels in North America, this project explores the intersections of biopolitics (specifically camp theory), queer theory, ecocriticism, and YA literature. Emily Danforth’s The Miseducation of Cameron Post and Nick White’s How to Survive a Summer are paired with scholars such as Gilles Deleuze, Felix Guattari, Joshua Whitehead, Greta Gaard, Hannah Arendt, Giorgio Agamben, Claudio Minca, Catriona Sandilands, Luce Irigaray, and Michael Marder to create a complex and intricate understanding of how ecologies impact queer youths’ experience in conversion therapy camps. The effect of such an intersectional and ecological understanding of queer becomings creates a foundation for further discovery and offers examples for current and future people to find mutual liberation with the ecologies we exist in.
Date: 1964-01-01
Access: Open access
- Bowdoin College Bulletin no. 350
Date: 2021-01-01
Creator: Gabrielle Vandendries
Access: Open access
- Photoacids, compounds that undergo excited state proton transfer (ESPT), have been utilized in different solar energy and lithographic applications.1, 2 The addition of functional groups and solvent can both change the ESPT mechanism of photoacids. In this study, the effect of solvent on the ESPT mechanism was explored using a model diprotic photoacid, 8-amino-2-naphthol (8N2OH). The photochemistry of 8N2OH in water and common nonaqueous solvents, acetonitrile, tetrahydrofuran (THF), and methanol, were studied using UV/Vis absorption, steady-state emission, and time-correlated single photon counting (TCPSC) emission spectroscopy. The results were analyzed using the Kamlet-Taft parameters. It was found that the ESPT mechanism of the cation in water is different from the mechanism in acetonitrile and THF. In water the excited cation forms the zwitterion, i.e. the OH site undergoes ESPT, while in acetonitrile and THF, the excited cation forms the neutral species, i.e. the NH3+ site undergoes ESPT. No ESPT was observed for 8N2OH in methanol. The effect of solvent mixtures on photoacidity was also investigated using acetonitrile and water mixtures. The solvent effects were more subtle; the time-resolved emission measurements showed the greatest stabilization of the excited neutral 8N2OH species at 20/80% acetonitrile-water mixtures. Finally, the ability to extend the solvent studies to ionic liquids, 1-ethyl-3-methylimidazolium (Im) trifluromethanesulfonate (OTF), was demonstrated. The combined studies reveal that solvent plays a large role in determining the ESPT mechanism and stabilization of 8N2OH.
Date: 1963-01-01
Access: Open access
- Bowdoin College Bulletin no. 346
Date: 1970-01-01
Access: Open access
- Bowdoin College Bulletin no. 374
Date: 1966-01-01
Access: Open access
- Bowdoin College Bulletin no. 358
Date: 2021-01-01
Creator: Gabby Unipan
Access: Open access
- This paper draws on data collected through in-depth interviews with multi-generational participants recruited from various online sites to explore the place-making strategies among lesbian, bisexual, and queer (LBQ) women and trans- and gender-non-conforming people (tgncp) during the Covid-19 pandemic. Historically denied public space, placemaking in immaterial space (i.e., digital spaces) has been essential to the production and maintenance of communities for LBQ women and tgncp. Because these populations rely on non-traditional placemaking strategies that are not always instantiated in material space, sociologists often overlook their efforts to create place for themselves. This paper corrects this omission by exploring how communities create place through the deployment of subcultural capital onto immaterial space. Introducing four main strategies of community placemaking, material-constant communities, material-transient communities, immaterial-constant communities, and immaterial-transient communities, this article expands sociological conceptions of space to accommodate the placemaking strategies of marginalized communities who might lack the economic and political resources to foster communities in material spaces. Beyond the investigation of lesbian-queer placemaking, this research contributes to the growing sociological literature exploring the multifaceted, fluid, contested, and ephemeral nature of place and placemaking in the context of increasing Internet use.
Date: 1914-01-01
Access: Open access
- Bowdoin College Bulletin no. 50

Date: 2014-05-01
Creator: Nathan D Ricke
Access: Access restricted to the Bowdoin Community
Date: 1982-11-11
Creator: Bruce D. Kohorn, Peter M.m. Rae
Access: Open access
- Tandem repeats of ribosomal RNA transcription units in Drosophila melanogaster are separated by a nontranscribed spacer that is comprised in part of serial repeats of a 0.24 kb sequence. DNA sequence analysis shows that such repeats are imperfect copies of a region that includes the site of in vivo rRNA transcription initiation (ca. -240 to +30). Subclones of the rDNA spacer that are copies of the sequence extending from -34 through the initiation site support detectable in vitro transcription in a mixture involving a Drosophila cell-free extract, but accurate in vitro transcription is considerably enhanced when a nontranscribed spacer template includes a copy of the sequence extending upstream of -34. From a comparison of the sequence and transcription template-effectiveness of various rDNA subclones, we infer that a major promoter of RNA polymerase I activity lies between -150 and -30 in the rDNA nontranscribed spacer. The nontranscribed spacer copies of the initiation region are less effective templates for transcription than is the region of in vivo initiation and there are differences between spacer repeates and the authentic sequence downstream of -240 that may account for this. © 1982 IRL Press Limited.
Date: 1995-06-01
Creator: F. Montes de Oca, M. L. Zeeman
Access: Open access
- We generalise and unify some recent results about extinction in nth-order nonautonomous competitive Lotka-Volterra systems. For each r ≤ n, we show that if the coefficients are continuous, bounded by strictly positive constants, and satisfy certain inequalities, then any solution with strictly positive initial values has the property that n - r of its components vanish, whilst the remaining r components asymptotically approach a canonical solution of an r-dimensional restricted system. In other words, r of the species being modeled survive whilst the remaining n - r are driven to extinction. © 1995 Academic Press, Inc.
Date: 1916-01-01
Access: Open access
- Bowdoin College Bulletin no. 61

Date: 2020-01-01
Creator: Grace Louise Cawdrey
Access: Access restricted to the Bowdoin Community

Date: 2020-01-01
Creator: Ilana R. Olin
Access: Access restricted to the Bowdoin Community
Date: 2011-12-01
Creator: Azer Akhmedov, Melanie Stein, Jennifer Taback
Access: Open access
- We produce a sequence of markings Sk of Thompson's group F within the space Gn of all marked n-generator groups so that the sequence (F, Sk) converges to the free group on n generators, for n ≥ 3. In addition, we give presentations for the limits of some other natural (convergent) sequences of markings to consider on F within G3, including (F, {x0, x1, xn}) and (F, {x0, x1, x0n}) © 2011 Springer Science+Business Media B.V.

- Embargo End Date: 2025-05-14
Date: 2020-01-01
Creator: Yujin Moon
Access: Embargoed
Date: 2005-09-22
Creator: Sean Cleary, Jennifer Taback
Access: Open access
- We explore the geometry of the Cayley graphs of the lamplighter groups and a wide range of wreath products. We show that these groups have dead end elements of arbitrary depth with respect to their natural generating sets. An element w in a group G with finite generating set X is a dead end element if no geodesic ray from the identity to w in the Cayley graph Γ(G, X) can be extended past w. Additionally, we describe some non-convex behaviour of paths between elements in these Cayley graphs and seesaw words, which are potential obstructions to these graphs satisfying the k-fellow traveller property. © The Author 2005. Published by Oxford University Press. All rights reserved.
Date: 2009-12-01
Creator: Bruce D. Kohorn, Susan Johansen, Akira Shishido, Tanya Todorova, Rhysly, Martinez, Elita Defeo, Pablo Obregon
Access: Open access
- The angiosperm extracellular matrix, or cell wall, is composed of a complex array of cellulose, hemicelluose, pectins and proteins, the modification and regulated synthesis of which are essential for cell growth and division. The wall associated kinases (WAKs) are receptor-like proteins that have an extracellular domain that bind pectins, the more flexible portion of the extracellular matrix, and are required for cell expansion as they have a role in regulating cellular solute concentrations. We show here that both recombinant WAK1 and WAK2 bind pectin in vitro. In protoplasts pectins activate, in a WAK2-dependent fashion, the transcription of vacuolar invertase, and a wak2 mutant alters the normal pectin regulation of mitogen-activated protein kinases. Microarray analysis shows that WAK2 is required for the pectin activation of numerous genes in protoplasts, many of which are involved in cell wall biogenesis. Thus, WAK2 plays a major role in signaling a diverse array of cellular events in response to pectin in the extracellular matrix. © 2009 Blackwell Publishing Ltd.
Date: 1973-01-01
Access: Open access
- "Catalogue published in conjunction with an exhibition held at the Bowdoin College Museum of Art, April 6-May 27, 1984"--T.p. verso
Date: 1974-01-01
Access: Open access
- Catalogue from a joint exhibition at Bowdoin College Museum of Art and the Museum of Fine Arts, Boston. Includes biographical references.
Date: 1979-01-01
Access: Open access
- "Exhibition dates: July 27-September 16, 1979." "Supported by the Maine State Commission on the Arts and the Humanities."
Date: 1990-01-01
Creator: Bruce D. Kohorn
Access: Open access
- Eukaryotic light harvesting proteins (LHCPs) bind pigments and assemble into complexes (LHCs) that channel light energy into photosynthetic reaction centers. The structures of several prokaryotic LHCPs are known and histidines are important for the binding of the associated pigments. It has been difficult to predict how the eukaryotic LHCPs associate with pigments as the structure of the major LHCP of photosystem II is not yet known. While each LHCPII binds approximately 13 chlorophylls the protein contains only three histidines, one in each putative transmembrane helix. Experiments that use isolated pea (Pisum sativum L.) chloroplasts and mutant LHCPII synthesized in vitro show that the substitution of either an alanine or an arginine for each histidine residue inhibits some aspect of LHCII assembly. The histidine of the first membrane helix, but not the second or third, may be involved in the transport across the chloroplast envelope. No histidine alone is essential for the insertion of LHCP into thylakoid membranes, yet arginine substitutions are more inhibitory than those of alanine. The histidine replacements have their most pronounced effect on the assembly of LHCP into LHCII.

- Restriction End Date: 2025-06-01
Date: 2020-01-01
Creator: Diana Katalina Grandas
Access: Access restricted to the Bowdoin Community
Date: 2019-01-01
Creator: Christopher Chong, Andre Foehr, Efstathios G. Charalampidis, Panayotis G. Kevrekidis, Chiara, Daraio
Access: Open access
- In this article, the existence, stability and bifurcation structure of time-periodic solutions (including ones that also have the property of spatial localization, i.e., breathers) are studied in an array of cantilevers that have magnetic tips. The repelling magnetic tips are responsible for the intersite nonlinearity of the system, whereas the cantilevers are responsible for the onsite (potentially nonlinear) force. The relevant model is of the mixed Fermi-Pasta-Ulam-Tsingou and Klein-Gordon type with both damping and driving. In the case of base excitation, we provide experimental results to validate the model. In particular, we identify regions of bistability in the model and in the experiment, which agree with minimal tuning of the system parameters. We carry out additional numerical explorations in order to contrast the base excitation problem with the boundary excitation problem and the problem with a single mass defect. We find that the base excitation problem is more stable than the boundary excitation problem and that breathers are possible in the defect system. The effect of an onsite nonlinearity is also considered, where it is shown that bistability is possible for both softening and hardening cubic nonlinearities.
Date: 2020-01-01
Creator: Emma Redington Lawry
Access: Open access
- Throughout the 21st century, certain facets of the democratic peace theory have informed American foreign policy, as policymakers credit democracy promotion with long-term stability and peace. In contrast, many political scientists have documented the often destabilizing and violent effects of democratization, particularly in underdeveloped states. How can we reconcile these tensions, and in what ways do they affect American foreign policy abroad? Under the lens of just war theory, or the doctrine of military ethics detailing the conditions under which it is morally acceptable to go to war, wage war and restore peace after war, this paper seeks to examine security sector reconstruction in post-counterinsurgency eras. In doing so, my analysis documents the effects of electoral processes on security and underscores the many difficulties of post-war rebuilding processes. In understanding these difficulties, I attempt to extract crucial lessons from the “best case” scenario of El Salvador and the “worst case” scenario of Iraq, both of which illuminate the fundamental tension between democratization and stability.
Date: 1908-01-01
Access: Open access
- Bowdoin College Bulletin no. 14
Date: 2007-03-01
Creator: Sean Cleary, Jennifer Taback
Access: Open access
- Rotation distance measures the difference in shape between binary trees of the same size by counting the minimum number of rotations needed to transform one tree to the other. We describe several types of rotation distance where restrictions are put on the locations where rotations are permitted, and provide upper bounds on distances between trees with a fixed number of nodes with respect to several families of these restrictions. These bounds are sharp in a certain asymptotic sense and are obtained by relating each restricted rotation distance to the word length of elements of Thompson's group F with respect to different generating sets, including both finite and infinite generating sets. © World Scientific Publishing Company.
Date: 2015-01-01
Access: Open access
- Published for the exhibition A Gift of Knowing: The Art of Dorothea Rockburne at the Bowdoin College Museum of Art from March 14 through April 26, 2015, supported by the Elizabeth B. G. Hamlin Fund and the Shapell Family Art Fund. Design by Wilcox Design, Cambridge, Massachusetts Copyright© 2015 Bowdoin College
Date: 1920-01-01
Access: Open access
- Bowdoin College Bulletin no. 98

- Restriction End Date: 2025-06-01
Date: 2020-01-01
Creator: Rhianna J Patel
Access: Access restricted to the Bowdoin Community
Date: 2012-05-01
Creator: Florence F. Sun, Justine E. Johnson, Martin P. Zeidler, Jack R. Bateman
Access: Open access
- Balancer chromosomes are critical tools for Drosophila genetics. Many useful transgenes are inserted onto balancers using a random and inefficient process. Here we describe balancer chromosomes that can be directly targeted with transgenes of interest via recombinase-mediated cassette exchange (RMCE). ©2012 Sun et al.

Date: 2020-01-01
Creator: Eskedar Girmash
Access: Access restricted to the Bowdoin Community

Date: 2020-01-01
Creator: Hannah D. Konkel
Access: Access restricted to the Bowdoin Community