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New data on metamorphic chlorite as a petrogenetic indicator mineral, with special regard to greenschist-facies rocks.
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Slaty cleavage: does layer silicate crystalchemistry play an auxiliary role inits development?
No full textCompositional controls on the cell dimensions of 2M1 muscovite and paragonite.
No full textMultivariant, second order regression equations have been developed to quantify the effects of Na* [= 100 Na/(Na + K)] and Fm [= (Fe(T) + Mg + Mn)] on the a, b, 1/2 c.sin beta, and V cell parameters of muscovite (143 specimens) and paragonite (22 specimens). Na* substitutions occur on the XII sites of these micas, and it is assumed that all Fm substitutions occur on the VI sites.
The Na* substitution has a strong effect on 1/2 c.sin beta and V and only a small effect on a and b. Fm substitution is largely restricted to muscovite and causes the a and b dimensions to increase. However, the associated increase of the a and b dimensions of the octahedral sheet necessitates rotations in the associated tetrahedral sheet such that the 1/2 c.sin beta dimension decreases concomitantly. The net effect of Fm substitution on cell volume is thus only a small increase.
Our regression equations for cell volume indicate that DELTA-V(mix) is positive for Na-bearing muscovites, but is either zero or slightly negative for K-bearing paragonites. A crystallochemical model is proposed to explain the latter behavior. These results may provide some insights on the effects of pressure on the solvus limbs, and a possible explanation of the low sodium-contents typical of phengitic muscovites, and the low phengite-contents typical of paragonites. These interrelations provide evidence which should enable formulation of better activity models for both paragonite and muscovite.
Previous attempts to use the muscovite-paragonite solvus as a geothermometer have yielded only semi-quantitative estimates of final equilibration temperatures. Applying the results obtained in this report should make it possible to significantly improve the accuracy of these temperature estimates
Crystal chemistry of some trioctahedral and dioctahedral micas coexisting in metamorphic sequences from N.W. Maine
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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
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
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