1,720,959 research outputs found
Recommended from our members
Assessment of Sulfide Intrusion and Genotypic Diversity in the Seagrass Halodule Wrightii from the Texas Gulf Coast
No full textSeagrasses are marine angiosperms that provide key ecological services to coastal areas. Unfortunately, seagrasses are experiencing a progressive decline, driven by natural and anthropogenic stressors, including sulfide (H2S) intrusion from high sediment sulfide concentrations. Seagrasses cope with sulfides through avoidance (reoxidation in the sediment) or tolerance (assimilation by tissues). Previous studies also suggested that seagrass response to environmental stress can be influenced and benefit from having genotypic (clonal) diversity. Although these mechanisms have been studied in some species, few have examined sulfide intrusion and its relation to genotypic diversity in seagrasses from the Texas Gulf Coast. In this study, we used stable sulfur isotopes and a microsatellite-based DNA marker assay to assess sulfide intrusion in the seagrass Halodule wrightii and investigate whether genotypic diversity plays a role in its response to sulfide stress. We found a gradient in δ34S values (-5.58 ± 0.54‰ to 13.58 ± 0.30‰), from roots to leaves, suggesting that H2S enters through underground tissues and is then distributed throughout the plant. The presence of sulfide-derived sulfur in varying proportions (15% to 76%) among the leaf, rhizome and root tissues indicates they are able to assimilate it into non-toxic, metabolic forms. Although sulfide intrusion did not significantly vary among the different genotypes (P > 0.05), this seagrass population had signs of being genetically diverse, indicating that it has the necessary genetic material to face and resist environmental stress. We hope that this study serves as the basis for further exploration of the genetics of sulfur assimilation and metabolism in seagrasses.Physical and Environmental SciencesCollege of Science and Engineerin
Recommended from our members
An assessment of hydrogen sulfide intrusion in the seagrass Halodule wrightii
No full textHydrogen sulfide (H2S, “sulfide”) is a naturally occurring component of the marine sediment. Eutrophi cation of coastal waters, however, can lead to an excess of sulfide production that can prove toxic to seagrasses. We used stable sulfur isotope ratio (δ34S) measurements to assess sulfide intrusion in the seagrass Halodule wrightii, a semi-tropical species found throughout the Gulf of Mexico, Caribbean Sea, and both western and eastern Atlantic coasts. We found a gradient in δ34S values ( 5.58 0.54‰þ 13.58 0.30‰) from roots to leaves, in accordance with prior observations and those from other species. The results may also represent the first values reported for H. wrightii rhizome tissue. The presence of sulfide-derived sulfur in varying proportions (15–55%) among leaf, rhizome, and root tissues suggests H. wrightii is able to assimilate sedimentary H2S into non-toxic forms that constitute a significant portion of the plant’s total sulfur content.This research was supported by a Graduate Research Award from the Texas Sea Grant program, a Hans and Patricia Suter Endowment Award from Texas A&M University-Corpus Christi, and by the Welch Foundation
Recommended from our members
Preparation of a reduced Cr2+ solution for sulfide distillation using a Jones Reductor
No full textThis protocol uses a Jones Reductor to prepare reduced Cr2+for the distillation of H2S from marine sediments. It is an adaptation of a protocol described by Backlund et al (DOI:https://doi.org/10.2137/1459606054224147
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
