Showing 751 - 760 of 4695 Items
Noether’s theorem for plane domains with hyperelliptic double
Date: 1977-01-01
Creator: William H. Barker
Access: Open access
- This paper is motivated by the observation that Noether’s theorem for quadratic differentials fails for hyperelliptic Riemann surfaces. In this paper we provide an appropriate substitute for Noether’s theorem which is valid for plane domains with hyperelliptic double. Our result is somewhat more explicit than Noether’s, and, in contrast with the case of nonhyperelliptic surfaces, it provides a basis for the (even) quadratic differentials which holds globally for all domains with hyperelliptic double. An important fact which plays a significant role in these considerations is that no two normal differentials of the first kind can have a common zero on a domain with hyperelliptic double. © 1977 Pacific Journal of Mathematics. All rights reserved.
Non-Naturalism and Naturalism in Mathematics, Morality, and Epistemology
Date: 2018-05-01
Creator: Nicholas DiStefano
Access: Open access
Policy Making, Decision Making, and Advocacy: The U.S. Asylum System Since 9/11
Date: 2024-01-01
Creator: Clara Jergins
Access: Open access
- Immigration justice advocates and immigration restrictionists alike are unhappy with the way that the U.S. asylum system functions. This project seeks to develop a better understanding of policy changes and the politicized influence of the president and executive authorities over the asylum system since 9/11—in particular, these individuals’ ability to implement their policy preferences through the hiring and instruction of Asylum Officers and Immigration Judges. Through case studies of nonprofit organizations, it identifies the key points in the asylum process where asylum has been restricted, and the ways in which these restrictions can be responded to. On the basis of these factors, this project identifies four key changes, made by Congress, through which the asylum system could be improved: the establishment of an Article I immigration court, encoded testimonial and credibility standards, universal representation, and an end to asylum seeker detention. These changes are asserted to depoliticize the asylum process and to create a stable asylum system in which those that should qualify for asylum do qualify.
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.
Prediction of a neuropeptidome for the eyestalk ganglia of the lobster Homarus americanus using a tissue-specific de novo assembled transcriptome
Date: 2017-03-01
Creator: Andrew E. Christie
Vittoria Roncalli
Matthew C. Cieslak
Micah G. Pascual
Andy, Yu
Tess J. Lameyer
Meredith E. Stanhope
Patsy S. Dickinson
Access: Open access
- In silico transcriptome mining is a powerful tool for crustacean peptidome prediction. Using homology-based BLAST searches and a simple bioinformatics workflow, large peptidomes have recently been predicted for a variety of crustaceans, including the lobster, Homarus americanus. Interestingly, no in silico studies have been conducted on the eyestalk ganglia (lamina ganglionaris, medulla externa, medulla interna and medulla terminalis) of the lobster, although the eyestalk is the location of a major neuroendocrine complex, i.e., the X-organ-sinus gland system. Here, an H. americanus eyestalk ganglia-specific transcriptome was produced using the de novo assembler Trinity. This transcriptome was generated from 130,973,220 Illumina reads and consists of 147,542 unique contigs. Eighty-nine neuropeptide-encoding transcripts were identified from this dataset, allowing for the deduction of 62 distinct pre/preprohormones. Two hundred sixty-two neuropeptides were predicted from this set of precursors; the peptides include members of the adipokinetic hormone-corazonin-like peptide, allatostatin A, allatostatin B, allatostatin C, bursicon α, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone (CHH), CHH precursor-related peptide, diuretic hormone 31, diuretic hormone 44, eclosion hormone, elevenin, FMRFamide-like peptide, glycoprotein hormone α2, glycoprotein hormone β5, GSEFLamide, intocin, leucokinin, molt-inhibiting hormone, myosuppressin, neuroparsin, neuropeptide F, orcokinin, orcomyotropin, pigment dispersing hormone, proctolin, pyrokinin, red pigment concentrating hormone, RYamide, short neuropeptide F, SIFamide, sulfakinin, tachykinin-related peptide and trissin families. The predicted peptides expand the H. americanus eyestalk ganglia neuropeptidome approximately 7-fold, and include 78 peptides new to the lobster. The transcriptome and predicted neuropeptidome described here provide new resources for investigating peptidergic signaling within/from the lobster eyestalk ganglia.
Distinct or shared actions of peptide family isoforms: II. Multiple pyrokinins exert similar effects in the lobster stomatogastric nervous system
Date: 2015-09-01
Creator: Patsy S. Dickinson
Sienna C. Kurland
Xuan Qu
Brett O. Parker
Anirudh, Sreekrishnan
Molly A. Kwiatkowski
Alex H. Williams
Alexandra B. Ysasi
Andrew E. Christie
Access: Open access
- Many neuropeptides are members of peptide families, with multiple structurally similar isoforms frequently found even within a single species. This raises the question of whether the individual peptides serve common or distinct functions. In the accompanying paper, we found high isoform specificity in the responses of the lobster (Homarus americanus) cardiac neuromuscular system to members of the pyrokinin peptide family: only one of five crustacean isoforms showed any bioactivity in the cardiac system. Because previous studies in other species had found little isoform specificity in pyrokinin actions, we examined the effects of the same five crustacean pyrokinins on the lobster stomatogastric nervous system (STNS). In contrast to our findings in the cardiac system, the effects of the five pyrokinin isoforms on the STNS were indistinguishable: they all activated or enhanced the gastric mill motor pattern, but did not alter the pyloric pattern. These results, in combination with those from the cardiac ganglion, suggest that members of a peptide family in the same species can be both isoform specific and highly promiscuous in their modulatory capacity. The mechanisms that underlie these differences in specificity have not yet been elucidated; one possible explanation, which has yet to be tested, is the presence and differential distribution of multiple receptors for members of this peptide family.
Related neuropeptides use different balances of unitary mechanisms to modulate the cardiac neuromuscular system in the American lobster, Homarus americanus
Date: 2015-01-01
Creator: Patsy S. Dickinson
Andrew Calkins
Jake S. Stevens
Access: Open access
- To produce flexible outputs, neural networks controlling rhythmic motor behaviors can be modulated at multiple levels, including the pattern generator itself, sensory feedback, and the response of the muscle to a given pattern of motor output. We examined the role of two related neuropeptides, GYSDRNYLRFamide (GYS) and SGRNFLRFamide (SGRN), in modulating the neurogenic lobster heartbeat, which is controlled by the cardiac ganglion (CG). When perfused though an isolated whole heart at low concentrations, both peptides elicited increases in contraction amplitude and frequency. At higher concentrations, both peptides continued to elicit increases in contraction amplitude, but GYS caused a decrease in contraction frequency, while SGRN did not alter frequency. To determine the sites at which these peptides induce their effects, we examined the effects of the peptides on the periphery and on the isolated CG. When we removed the CG and stimulated the motor nerve with constant bursts of stimuli, both GYS and SGRN increased contraction amplitude, indicating that each peptide modulates the muscle or the neuromuscular junction. When applied to the isolated CG, neither peptide altered burst frequency at low peptide concentrations; at higher concentrations, SGRN decreased burst frequency, whereas GYS continued to have no effect on frequency. Together, these data suggest that the two peptides elicit some of their effects using different mechanisms; in particular, given the known feedback pathways within this system, the importance of the negative (nitric oxide) relative to the positive (stretch) feedback pathways may differ in the presence of the two peptides.
The neuromuscular transform of the lobster cardiac system explains the opposing effects of a neuromodulator on muscle output
Date: 2013-10-18
Creator: Alex H. Williams
Andrew Calkins
Timothy O'Leary
Renee Symonds
Eve, Marder
Patsy S. Dickinson
Access: Open access
- Motor neuron activity is transformed into muscle movement through a cascade of complex molecular and biomechanical events. This nonlinear mapping of neural inputs to motor behaviors is called the neuromuscular transform (NMT). We examined the NMT in the cardiac system of the lobster Homarus americanus by stimulating a cardiac motor nerve with rhythmic bursts of action potentials and measuring muscle movements in response to different stimulation patterns. The NMT was similar across preparations, which suggested that it could be used to predict muscle movement from spontaneous neural activity in the intact heart. We assessed this possibility across semi-intact heart preparations in two separate analyses. First, we performed a linear regression analysis across 122 preparations in physiological saline to predict muscle movements from neural activity. Under these conditions, the NMT was predictive of contraction duty cycle but was unable to predict contraction amplitude, likely as a result of uncontrolled interanimal variability. Second, we assessed the ability of the NMT to predict changes in motor output induced by the neuropeptide C-type allatostatin. Wiwatpanit et al. (2012) showed that bath application of C-type allatostatin produced either increases or decreases in the amplitude of the lobster heart contractions. We show that an important component of these preparation-dependent effects can arise from quantifiable differences in the basal state of each preparation and the nonlinear form of the NMT. These results illustrate how properly characterizing the relationships between neural activity and measurable physiological outputs can provide insight into seemingly idiosyncratic effects of neuromodulators across individuals. © 2013 the authors.
C-terminal methylation of truncated neuropeptides: An enzyme- assistedextraction artifact involving methanol
Date: 2013-01-01
Creator: Elizabeth A. Stemmler
Elizabeth E. Barton
Onyinyechi K. Esonu
Daniel A. Polasky
Laura L., Onderko
Audrey B. Bergeron
Andrew E. Christie
Patsy S. Dickinson
Access: Open access
- Neuropeptides are the largest class of signaling molecules used by nervous systems. Today, neuropeptidediscovery commonly involves chemical extraction from a tissue source followed by mass spectrometriccharacterization. Ideally, the extraction procedure accurately preserves the sequence and any inher-ent modifications of the native peptides. Here, we present data showing that this is not always true.Specifically, we present evidence showing that, in the lobster Homarus americanus, the orcokinin fam-ily members, NFDEIDRSGFG-OMe and SSEDMDRLGFG-OMe, are non-native peptides generated fromfull-length orcokinin precursors as the result of a highly selective peptide modification (peptide trun-cation with C-terminal methylation) that occurs during extraction. These peptides were observed byMALDI-FTMS and LC-Q-TOFMS analyses when eyestalk ganglia were extracted in a methanolic solvent,but not when tissues were dissected, co-crystallized with matrix, and analyzed directly with methanolexcluded from the sample preparation. The identity of NFDEIDRSGFG-OMe was established using MALDI-FTMS/SORI-CID, LC-Q-TOFMS/MS, and comparison with a peptide standard. Extraction substitutingdeuterated methanol for methanol confirmed that the latter is the source of the C-terminal methyl group,and MS/MS confirmed the C-terminal localization of the added CD3. Surprisingly, NFDEIDRSGFG-OMe isnot produced via a chemical acid-catalyzed esterification. Instead, the methylated peptide appears toresult from proteolytic truncation in the presence of methanol, as evidenced by a reduction in conver-sion with the addition of a protease-inhibitor cocktail; heat effectively eliminated the conversion. Thisunusual and highly specific extraction-derived peptide conversion exemplifies the need to consider bothchemical and biochemical processes that may modify the structure of endogenous neuropeptides. © 2013 The Authors. Published by Elsevier Inc. All rights reserved.
The quantitative genetics of incipient speciation: Heritability and genetic correlations of skeletal traits in populations of diverging favia fragum ecomorphs
Date: 2011-12-01
Creator: David B. Carlon
Ann F. Budd
Catherine Lippé
Rose L. Andrew
Access: Open access
- Recent speciation events provide potential opportunities to understand the microevolution of reproductive isolation. We used a marker-based approach and a common garden to estimate the additive genetic variation in skeletal traits in a system of two ecomorphs within the coral species Favia fragum: a Tall ecomorph that is a seagrass specialist, and a Short ecomorph that is most abundant on coral reefs. Considering both ecomorphs, we found significant narrow-sense heritability (h 2) in a suite of measurements that define corallite architecture, and could partition additive and nonadditive variation for some traits. We found positive genetic correlations for homologous height and length measurements among different types of vertical plates (costosepta) within corallites, but negative correlations between height and length within, as well as between costosepta. Within ecomorphs, h 2 estimates were generally lower, compared to the combined ecomorph analysis. Marker-based estimates of h 2 were comparable to broad-sense heritability (H) obtained from parent-offspring regressions in a common garden for most traits, and similar genetic co-variance matrices for common garden and wild populations may indicate relatively small G × E interactions. The patterns of additive genetic variation in this system invite hypotheses of divergent selection or genetic drift as potential evolutionary drivers of reproductive isolation. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.