Showing 211 - 220 of 4695 Items
Identification and cardiotropic actions of sulfakinin peptides in the American lobster Homarus americanus
Date: 2007-07-01
Creator: Patsy S. Dickinson
Jake S. Stevens
Szymon Rus
Henry R. Brennan
Christopher C., Goiney
Christine M. Smith
Lingjun Li
David W. Towle
Andrew E. Christie
Access: Open access
- In arthropods, a group of peptides possessing a -Y(SO3H)GHM/ LRFamide carboxy-terminal motif have been collectively termed the sulfakinins. Sulfakinin isoforms have been identified from numerous insect species. In contrast, members of this peptide family have thus far been isolated from just two crustaceans, the penaeid shrimp Penaeus monodon and Litopenaeus vannamei. Here, we report the identification of a cDNA encoding prepro-sulfakinin from the American lobster Homarus americanus. Two sulfakinin-like sequences were identified within the open-reading frame of the cDNA. Based on modifications predicted by peptide modeling programs, and on homology to the known isoforms of sulfakinin, particularly those from shrimp, the mature H. americanus sulfakinins were hypothesized to be pEFDEY(SO3H)GHMRFamide (Hoa-SK I) and GGGEY(SO3H)DDY(SO3H)GHLRFamide (Hoa-SK II). Hoa-SK I is identical to one of the previously identified shrimp sulfakinins, while Hoa-SK II is a novel isoform. Exogenous application of either synthetic Hoa-SK I or Hoa-SK II to the isolated lobster heart increased both the frequency and amplitude of spontaneous heart contractions. In preparations in which spontaneous contractions were irregular, both peptides increased the regularity of the heartbeat. Our study provides the first molecular characterization of a sulfakinin-encoding cDNA from a crustacean, as well as the first demonstration of bioactivity for native sulfakinins in this group of arthropods.
Trumpet slices in Kerr spacetimes
Date: 2014-12-29
Creator: Kenneth A. Dennison
Thomas W. Baumgarte
Pedro J. Montero
Access: Open access
- We introduce a new time-independent family of analytical coordinate systems for the Kerr spacetime representing rotating black holes. We also propose a (2+1)+1 formalism for the characterization of trumpet geometries. Applying this formalism to our new family of coordinate systems we identify, for the first time, analytical and stationary trumpet slices for general rotating black holes, even for charged black holes in the presence of a cosmological constant. We present results for metric functions in this slicing and analyze the geometry of the rotating trumpet surface.
Bilad al-brazil: The importance of west african scholars in brazilian islamic education and practice in historic and contemporary perspective
Date: 2021-02-01
Creator: Ayodeji Ogunnaike
Access: Open access
- While it is well established now that the middle passage did not entirely separate Africans who were forcibly brought to the Americas from their home cultures and traditions, these connections are often studied and understood in the form of survivals or ancestral memory. This paper argues that in major urban centers in Brazil until around the time of World War I, West Africans not only managed to recreate Islamic communities and intellectual traditions, but maintained important contacts with their homelands. In much the same way that scholars have argued that the Sahara constituted an avenue of exchange and connection between North Africa and Bilad al-Sudan, I argue here that the Atlantic Ocean was not an insurmountable barrier but provided opportunities for African Muslims to extend the traditions of Bilad al-Sudan into Brazil—albeit to a much lesser extent.
Monteverde: ecología y conservación de un bosque nuboso tropical
Date: 2014-12-01
Creator: Nathaniel T Wheelwright
Nalini M Nadkarni
Access: Open access
- La Reserva Biológica Bosque Nuboso Monteverde ha capturado la atención mundial de biólogos, conservacionistas y ecólogos y allí se han hecho vastas investigaciones durante los últimos 40 años. Unos 40.000 ecoturistas visitan el Bosque Nuboso cada año y se considera el bosque lluvioso arquetípico de las altitudes altas. Este libro, una traducción actualizada de "Monteverde: Ecology and Conservation of a Tropical Cloud Forest", editado por Nalini Nadkarni y Nathaniel T. Wheelwright (Oxford University Press, 2000) presenta capítulos sintéticos y recuentos específicos escritos por más de 100 biólogos y residentes locales. En un solo volumen documenta todo lo que se sabe en 2014 de la diversidad biológica de Monteverde, Costa Rica, y cómo protegerla. The Monteverde Cloud Forest Reserve has captured the worldwide attention of biologists, conservationists, and ecologists and has been the setting for extensive investigation over the past 40 years. Roughly 40,000 ecotourists visit the Cloud Forest each year, and it is often considered the archetypal high-altitude rain forest. This book, an updated and expanded version of "Monteverde: Ecology and Conservation of a Tropical Cloud Forest", edited by Nalini Nadkarni and Nathaniel T. Wheelwright (Oxford University Press, 2000), features synthetic chapters and specific accounts written by more than 100 biologists and local residents. The 862-page book includes 12 new short chapters and documents in a single volume everything known in 2014 about the biological diversity of Monteverde, Costa Rica, and how to protect it.
Three-Year-Old Agents of Social Change: How aeioTU Educators Build on Children’s Agency
Date: 2024-01-01
Creator: Andrea Rodriguez
Access: Open access
- aeioTU is a Colombian organization that works to enact social change through the field of early childhood education. In collaboration with the Colombian government, aeioTU oversees several public centers located in socioeconomically vulnerable municipalities in Colombia. This thesis analyzes the aeioTU curriculum and the practices of several aeioTU teachers through the theoretical lens of Freire’s critical pedagogy. This thesis argues that by fostering critical awareness of the world from an early age, as well as by collaborating closely with mothers and the communities at large, aeioTU teachers equip children with the tools to become social agents who can challenge and positively change their lived realities. The research presented in this thesis affirms the potential of aeioTU teachers to enact social change in socioeconomically vulnerable communities by building on young children’s social agency.
Color-factor symmetry and BCJ relations for QCD amplitudes
Date: 2016-11-01
Creator: Robert W. Brown
Stephen G. Naculich
Access: Open access
- Tree-level n-point gauge-theory amplitudes with n − 2k gluons and k pairs of (massless or massive) particles in the fundamental (or other) representation of the gauge group are invariant under a set of symmetries that act as momentum-dependent shifts on the color factors in the cubic decomposition of the amplitude. These symmetries lead to gauge-invariant constraints on the kinematic numerators. They also directly imply the BCJ relations among the Melia-basis primitive amplitudes previously obtained by Johansson and Ochirov.
An overview of approaches and challenges for retrieving marine inherent optical properties from ocean color remote sensing
Date: 2018-01-01
Creator: P. Jeremy Werdell
Lachlan I.W. McKinna
Emmanuel Boss
Steven G. Ackleson
Susanne E., Craig
Watson W. Gregg
Zhongping Lee
Stéphane Maritorena
Collin S. Roesler
Cécile S. Rousseaux
Dariusz Stramski
James M. Sullivan
Michael S. Twardowski
Maria Tzortziou
Xiaodong Zhang
Access: Open access
- Ocean color measured from satellites provides daily global, synoptic views of spectral water-leaving reflectances that can be used to generate estimates of marine inherent optical properties (IOPs). These reflectances, namely the ratio of spectral upwelled radiances to spectral downwelled irradiances, describe the light exiting a water mass that defines its color. IOPs are the spectral absorption and scattering characteristics of ocean water and its dissolved and particulate constituents. Because of their dependence on the concentration and composition of marine constituents, IOPs can be used to describe the contents of the upper ocean mixed layer. This information is critical to further our scientific understanding of biogeochemical oceanic processes, such as organic carbon production and export, phytoplankton dynamics, and responses to climatic disturbances. Given their importance, the international ocean color community has invested significant effort in improving the quality of satellite-derived IOP products, both regionally and globally. Recognizing the current influx of data products into the community and the need to improve current algorithms in anticipation of new satellite instruments (e.g., the global, hyperspectral spectroradiometer of the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission), we present a synopsis of the current state of the art in the retrieval of these core optical properties. Contemporary approaches for obtaining IOPs from satellite ocean color are reviewed and, for clarity, separated based their inversion methodology or the type of IOPs sought. Summaries of known uncertainties associated with each approach are provided, as well as common performance metrics used to evaluate them. We discuss current knowledge gaps and make recommendations for future investment for upcoming missions whose instrument characteristics diverge sufficiently from heritage and existing sensors to warrant reassessing current approaches.
BCJ relations from a new symmetry of gauge-theory amplitudes
Date: 2016-10-01
Creator: Robert W. Brown
Stephen G. Naculich
Access: Open access
- We introduce a new set of symmetries obeyed by tree-level gauge-theory amplitudes involving at least one gluon. The symmetry acts as a momentum-dependent shift on the color factors of the amplitude. Using the radiation vertex expansion, we prove the invariance under this color-factor shift of the n-gluon amplitude, as well as amplitudes involving massless or massive particles in an arbitrary representation of the gauge group with spin zero, one-half, or one. The Bern-Carrasco-Johansson relations are a direct consequence of this symmetry. We also introduce the cubic vertex expansion of an amplitude, and use it to derive a generalized-gauge-invariant constraint on the kinematic numerators of the amplitude. We show that the amplitudes of the bi-adjoint scalar theory are invariant under the color-factor symmetry, and use this to derive the null eigenvectors of the propagator matrix. We generalize the color-factor shift to loop level, and prove the invariance under this shift of one-loop n-gluon amplitudes in any theory that admits a color-kinematic-dual representation of numerators. We show that the one-loop color-factor symmetry implies known relations among the integrands of one-loop color-ordered amplitudes.
Genome plasticity in candida albicans is driven by long repeat sequences
Date: 2019-06-01
Creator: Robert T. Todd
Tyler D. Wikoff
Anja Forche
Anna Selmecki
Access: Open access
- Genome rearrangements resulting in copy number variation (CNV) and loss of heterozygosity (LOH) are frequently observed during the somatic evolution of cancer and promote rapid adaptation of fungi to novel environments. In the human fungal pathogen Candida albicans, CNV and LOH confer increased virulence and antifungal drug resistance, yet the mechanisms driving these rearrangements are not completely understood. Here, we unveil an extensive array of long repeat sequences (65–6499 bp) that are associated with CNV, LOH, and chromosomal inversions. Many of these long repeat sequences are uncharacterized and encompass one or more coding sequences that are actively transcribed. Repeats associated with genome rearrangements are predominantly inverted and separated by up to ~1.6 Mb, an extraordinary distance for homology-based DNA repair/recombination in yeast. These repeat sequences are a significant source of genome plasticity across diverse strain backgrounds including clinical, environmental, and experimentally evolved isolates, and represent previously uncharacterized variation in the reference genome.