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Correlation between magnetic anisotropy and phyllosilicate preferred orientation for various sedimentary rocks.
No full textThe low and high-field magnetic anisotropy (AMS, HFA) of the various sedimentary and anchimetamorphic rocks was compared to the theoretical anisotropy calculated from the neutron texture goniometry measurements. The studied rocks range from Pliocene to Pleistocene clays and marls of southern Italy to Palaeozoic mudstones and greywackes of the Rhenohercynian Zone of the Czech Republic.The magnetic anisotropy of studied rocks is predominantly carried by the paramagnetic phyllosilicates, i.e. chlorite and, to the minor extent, micas. The orientation tensors of the phyllosilicate (001) planes were calculated from the neutron goniometry pole figures. Subsequently, the principal values of the theoretical anisotropy were calculated from the principal values of the orientation tensor assuming the various anisotropy values for the phyllosilicates grains. As only the paramagnetic anisotropy should be correlated with the preferred orientation of phyllosilicate phases, the HFA was used for the separation of the paramagnetic and ferromagnetic contribution to the magnetic anisotropy.In most cases, the principal directions of the AMS, high-field paramagnetic component (HFP), and the theoretical anisotropy are subparallel (Fig. 1). No systematic deviation of paramagnetic fabric from whole-rock magnetic fabric can be observed.Quantitative correlations were presented in terms of the standard deviatoric susceptibility, k’, and the difference shape factor, U, expressing anisotropy degree and shape, respectively (Fig. 2). The degrees of the theoretical anisotropy, AMS, and HFP correlate very well (correlation coefficient, R > 0.95) implying nearly the same degree of anisotropy for all the employed methods. The correlations of the shapes of respective anisotropies show more significant scatters. Despite this dispersion, the prolate and oblate shapes still remain well defined.This integrated approach enables to establish a more accurate qualitative and quantitative correlation between the phyllosilicate fabric and magnetic anisotropy and yields valuable information about the meaning of the magnetic fabri
Neutron pole figures compared with magnetic preferred orientations of different rock types
No full textThe magnetic fabric in “undeformed clays”: AMS and neutron texture analyses from the Rif Chain (Morocco)
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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
Combined Neutron Texture and Magnetic Analyses on “Undeformed” Clays: the Origin of Tectonic Lineations in Extensional Basins
No full textIn extensional sedimentary basins it has been demonstrated that fine-grained sediments that do not appear deformed at the outcrop scale can carry a magnetic fabric consistent with the regional deformation. In this study, carried out on clays from extensional basins in southern Italy, the magnetic lineation is tectonically controlled and oriented perpendicularly to the main normal faults. As the origin of such magnetic lineation is not yet well understood, we present combination of magnetic and textural analyses in order to unravel that phenomenon.A combination of low-field, high-field and low-temperature measurements was used in order to distinguish the ferrimagnetic and paramagnetic contribution to the magnetic susceptibility and its anisotropy. The magnetic anisotropy of studied sediments is predominantly carried by the paramagnetic phyllosilicates. Neutron texture analysis was used to evaluate the spatial distribution of the basal planes of chlorite. Results demonstrate that the orientation of the magnetic lineation is related to the spatial distribution of phyllosilicate minerals, lying parallel to the common axis of differently oriented basal planes. Independent of the chlorite basal planes distribution (from an axial symmetric to a girdle pattern in the bedding plane, due to their progressive “crenulation”), the AMS magnetic lineation is always parallel to the minimum axis of the mineral fabric ellipsoid.In order to make a quantitative correlation between the AMS and rock fabric, the low- and high-field magnetic anisotropy (AMS, HFA) were compared to the theoretical anisotropy calculated from the neutron texture goniometry measurements. Quantitative correlation is presented in terms of the standard deviatoric susceptibility, k’, and the difference shape factor, U, expressing anisotropy degree and shape, respectively. The degrees of the theoretical anisotropy, AMS, and HFP correlate very well implying nearly the same degree of anisotropy for all the employed methods. When ellipsoid shape is considered, the prolate and oblate shapes are well defined between respective methods
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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