1,721,216 research outputs found
Magnetic enhancement is linked to and precedes hematite formation in aerobic soil
No full textSoil formation usually increases magnetic susceptibility, most often by increasing the concentrations of magnetite and maghemite, which are two ferrimagnetic iron oxides. Here we provide evidence that magnetic enhancement in aerobic soils not affected by detrital magnetic inputs or thermal transformation of other iron oxides is mostly due to the formation of maghemite, which is later transformed into hematite—the iron oxide that gives red color to soil. We show that the maghemite/hematite ratio is influenced by the particular environment and the degree of soil development, so it constitutes an effective tool for paleoenvironmental and planetary studies
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
Contrasting behavior of hematite and goethite within paleosol S5 of the Luochuan profile, Chinese Loess Plateau
No full textThe Chinese loess/paleosol sequence provides an excellent record of long-term variations in the East Asian paleomonsoon. For representative loess profiles, paleosol units have enhanced magnetic properties compared to loess units. However, at some depth intervals with special paleoenvironmental conditions, selective depletion of antiferromagnetic (AFM) minerals (hematite and goethite) could occur, resulting in complexities in accurately linking variations in magnetic properties to long-term fluctuations in paleoclimate. To resolve this problem, we directly measured the mass concentrations of these AFM minerals using second-order diffuse reflectance spectroscopy (DRS), and then correlated the DRS results to high-field isothermal remanent magnetization (HIRM) from paleosol unit S5 at the Luochuan profile, central Chinese Loess Plateau. Our results suggest that a low HIRM anomaly just below the sub-paleosol unit S5S1 is caused by fluctuations specifically in goethite content, while the hematite concentration exhibits a maximum over the same depth interval. This appears to rule out significant loss of hematite to reductive dissolution and further indicates that hematite and goethite may respond differently to changes in the paleoclimate condition
Variazioni delle proprietà di superficie e dell'adsorbimento di fosforo in campioni di Terra Rossa trattati con DCB
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The contrasting effect of goethite and hematite on phosphate sorption and desorption by Terra Rossa
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