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Microstructure evolution in marble tectonites within a crustal-scale shear zone (Alpi Apuane, Italy)
No full text
Strain dependent variation of microstructure and texture in naturally deformed Carrara marble
No full textThis study investigates the microstructure and texture variations across a mm-scale shear zone in Carrara marble of the Alpi Apuane (Italy).
The microstructures have been investigated for grain size, texture, and shape fabrics. Textures have been measured with Computer-Integrated
Polarization Microscopy (CIP) and Electron Back Scattered Diffraction (EBSD) separating porphyroclast and recrystallized grains. The deformation,
which post-dates an earlier deformation phase and subsequent annealing, is strongly localized. The microstructures and textures change
across the shear strain gradient and are interpreted to preserve a time sequence of progressive stages of deformation. The bulk shear strain rate is
estimated to be about 1011 sec1 at deformation temperatures of approximately 325 C 30 C.
The protomylonite is characterized by a core mantle structure with a bimodal grain size distribution which changes gradually to a completely
dynamically recrystallized microstructure with a unimodal grain size distribution in the mylonitic center of the shear zone. Core-mantlestructures
are produced by dominant rotation recrystallization accompanied by some grain boundary migration. The microstructural transition
from protomylonite to mylonite coincides with a change in texture. With increasing strain the single c-axis maximum of an earlier inherited
texture in the protomylonite is replaced by a similar texture in a different orientation (maximum normal to the shear plane) which is consistent
with dominant basal hai and r h2201i slip. The microstructural and textural variations depend on the proportion of recrystallized grains. As
dynamic recrystallization progresses with finite strain the texture development is finite strain-dependent. The comparison of the microstructures
and textures to other natural and to experimental examples explains the progressive change of the texture and demonstrates the texture evolution
produced by dynamic recrystallization
Microstructure evolution in marble tectonites within a crustal scale shear zone (Alpi Apuane, Italy)
No full textMicrofabric study on the deformational and thermal history of the Alpi Apuane marbles (Carrara marbles, Italy)
No full textMicrofabric study on the deformational and thermal history of the Alpi Apuane marbles (Carrara marbles), Italy
No full textMarbles from different geometrical and structural positions within the Alpi Apuane metamorphic complex show a large variability in microfabric types as indicated by microstructure, c-axis orientation and temperature analysis. Statically recrystallized samples showing a granoblastic microstructure and polygonal grain boundaries are characterized by a grain size variation from east to west from 80-100 μm to 250-300 μm. This is correlated with an equilibration calcite-dolomite temperature from 360-380°C to 420°-430°C. Two kinds of dynamically recrystallized microstructures have been investigated: a first one exhibiting coarse grains (150-200 μm) with lobate grain boundaries and a strong shape preferred orientation and a second one characterized by a smaller grain size (40-50 μm) and predominantly straight grain boundaries. These microstructural types, associated with localized post-thermal peak shear zones and meter- to kilometer-scale folds, are interpreted as related to high strain and high temperature crystal plastic deformation mechanisms (dislocation creep) associated with predominant grain boundary migration (type-B1) or subgrain-rotation recrystallization (type-B2). These differences in dynamically recrystallized microstructures are related to equilibration temperatures higher in type-B1 (390°C) than in type-B2 (370-340°C). We have been able to relate the development of the different microfabric types to the successive stages of deformation of the Alpi Apuane metamorphic complex. (C) 2000 Elsevier Science Ltd. All rights reserved.
Marbles from different geometrical and structural positions within the Alpi Apuane metamorphic complex show a large variability in microfabric types as indicated by microstructure, c-axis orientation and temperature analysis. Statically recrystallized samples showing a granoblastic microstructure and polygonal grain boundaries are characterized by a grain size variation from east to west from 80-100 μm to 250-300 μm. This is correlated with an equilibration calcite-dolomite temperature from 360-380°C to 420°-430°C. Two kinds of dynamically recrystallized microstructures have been investigated: a first one exhibiting coarse grains (150-200 μm) with lobate grain boundaries and a strong shape preferred orientation and a second one characterized by a smaller grain size (40-50 μm) and predominantly straight grain boundaries. These microstructural types, associated with localized post-thermal peak shear zones and meter- to kilometer-scale folds, are interpreted as related to high strain and high temperature crystal plastic deformation mechanisms (dislocation creep) associated with predominant grain boundary migration (type-B1) or subgrain-rotation recrystallization (type-B2). These differences in dynamically recrystallized microstructures are related to equilibration temperatures higher in type-B1 (390°C) than in type-B2 (370-340°C). We have been able to relate the development of the different microfabric types to the successive stages of deformation of the Alpi Apuane metamorphic complex
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
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