1,720,969 research outputs found
Microscopy and spectroscopy with X-rays for studies in the environmental sciences
No full textX-ray spectromicroscopy is a powerful tool for addressing key questions in the environmental sciences due to its high spectral and spatial resolution. It has been used successfully for material research, biology and environmental studies, e.g. in the form of mu-X-ray fluorescence and spectromicroscopy with a spatial resolution of <100 nm. With the combination of high-resolution microscopy and spectroscopy it is possible to determine elemental composition as well as chemical speciation, and also identify trace elements to nm-resolution. Samples from soils and groundwater aquifers have been imaged to visualize the appearance of structures on the nm- and mu m-scale. The effect of changing chemical conditions in ail aqueous environment on the appearance of these structures has been imaged and evaluated. Clay dispersions, microhabitats and morphological effects of biologically-induced redox changes Of humic substances have been imaged tomographically, conveying a detailed three-dimensional presentation of the specimen structure. Using the spectromicroscopy potential, the distribution of organic and inorganic components, as well as different inorganic components, has been studied. Spectra were analysed for major chemical constituents and were used, for example, to assess different sulphur species in ail entire soil profile
Visualizing the dynamics of soil aggregation as affected by arbuscular mycorrhizal fungi
No full textStable soils provide valuable ecosystem services and mechanical soil stability is enhanced by the presence of arbuscular mycorrhizal fungi (AMF). Soil aggregation, which is the major driver of mechanical soil stability, is often treated as a static phenomenon, even though aggregate turnover is continually ongoing. In fact, some breakdown of macroaggregates is
necessary to allow new aggregate formation and inclusion of new organic matter into microaggregates. We determined how aggregate turnover times were affected by AMF by tracking movement of rare earth elements (REE), applied as their immobile oxides, between aggregate size classes, and using X-ray fluorescence microscopy to spatially localize REEs in a sample of aggregates. Here we show that AMF increased large macroaggregate formation and slowed down disintegration of large and small macroaggregates. Microaggregate turnover was increased in the presence of AMF. Internal aggregate organization suggested that although formation of microaggregates by accretion of soil to particulate organic matter is common, it is not the only mechanism in operation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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