1,720,980 research outputs found
Problematic Mesoproterozoic fossil Horodyskia from Glacier National Park, Montana, USA
No full textString-of-beads fossils (Horodyskia moniliformis and Horodyskia williamsii) from the 1.48 Ga lower Appekunny Argillite of Glacier National Park have been re-examined, and collected from both scree, which yielded most prior specimens, as well as outcrops. The fossils come from laminated silty shales and carbonaceous-swirl shales, with local sandstone paleochannels, interpreted as a very shallow lake margin. Very weakly developed paleosols also are present, but do not contain Horodyskia, which lived in very shallow water, seldom exposed and rilled. Chemical index of alteration at horizons with Horodyskia are evidence of a warm temperate to subtropical humid paleoclimate, unlike arid and cool paleoclimates at other stratigraphic levels in the Belt Supergroup. Thin section examination reveals that the beads are associated with a system of tubes, including connecting strings, and other tubes radiating outward from each bead. Partial burial and branching of these tubes may be evidence of a benthic sessile life style. A variety of explanations for Horodyskia are falsified by our new observations: including pseudofossil, dubiofossil, prokaryotic colony, foraminifera, slime mold, puffball fungus, brown alga, sponge, hydrozoan or bryozoan colony, or metazoan fecal string. Our remaining working hypothesis is that Horodyskia beads were endolichen bladders, comparable with living Geosiphon pyriformis (Archaeosporales, Glomeromycota, Fungi), which has heterocystic cyanobacterial photosymbionts (Nostoc punctiforme). This hypothesis is not without problems, because bladders of Geosiphon are mostly erect and clavate, but beadlike only in early growth stages, form clusters or close strings rather than elongate strings, and are terrestrial rather than aquatic. Nevertheless this new hypothesis for Horodyskia is compatible with what little is known about fungal evolution, and testable by additional studies of its paleoenvironments and associated fossils
Stomatal index of Ginkgo biloba as a proxy for atmospheric CO2
No full textThis thesis presents a new calibration of the Ginkgo stomatal index as a proxy for atmospheric CO2 concentrations using leaves from modern Ginkgo biloba herbarium specimens. Scanning electron images were obtained to count stomates and cells on leaves collected between 1829 and 2015. Average stomatal index (SI) was then calculated for each year. SI is defined as #stomates/(#stomates + # epidermal cells)*100. The relationship between stomatal index and atmospheric CO2 can be expressed in an equation following the form recommended by Wynn (2003), as the most likely representation of the physical laws governing CO2 diffusion across stomates. The new fitted equation for determining CO2 from Ginkgo SI is: CO2=205.7+13,630,000 x SI^(-5.224). This new equation is applied to suitably preserved Cenozoic fossil leaves of Ginkgo and results in a downward revision of estimated CO2 levels, while preserving the general shape of greenhouse spikes in the middle Miocene and Eocene. These spikes correlate to climatic warm and wet spikes derived from paleosol evidence during those times.10000-01-0
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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