1,720,961 research outputs found
Overview of CRM-bearing minerals in the Co-Ni-As mineralisation of the Punta Corna mining complex, Northern Italy
No full textThe Punta Corna mining district, located in the Lanzo Valleys area of Western Alps (Northern Italy), is a
system of hydrothermal veins which were exploited in the past for Fe, Ag and later Co. These veins are hosted
within metaophiolitic rocks (metabasalts with minor metagabbros, ultramafic rocks and minor metasediments)
representing disrupted sections of oceanic lithosphere of Jurassic age. The mineralization is characterized by
Co-Ni arsenides in the Eastern sector of Punta Corna, and by siderite in the Western sector, where Co phases
are less abundant. Four deposition stages have been recognized (Moroni et al., 2019): i) siderite, ii) baryte, iii)
Co-Ni-Fe arsenide, and vi) sulfides and sulfosalts.
This work focuses on the mineralogy and mineral chemistry of CRM-bearing minerals, deposited mainly
during the third and fourth stages, in selected mining sites of Punta Corna. The selected mining sites are:
San Francesco and Sant’Andrea in the Western part of Punta Corna; Vittorio Amedeo, Nido dell’Aquila, San
Giovanni, Carlo Emanuele, Santa Maria, Speranza and Colle Fortuna in the Eastern part; Santa Barbara in the
Southern part.
The main CRM phases are: ferroskutterudite (Fe,Co)As3, safflorite (Co,Fe)As2, clinosafflorite (Co,Fe,Ni)
As2, tetrahedrite (Cu,Fe)12Sb4S13, bismuthian tetrahedrite (Cu,Fe)12(Sb,Bi)4S13, bournonite PbCuSbS3,
pyrargyrite Ag3SbS3, a Bi-rich variety of chalcostibite CuSbS2 and an Sb-Bi alloy. Moreover, tiny xenotime
(YPO4) crystals have been detected in some samples.
Co-bearing minerals occur mainly in Eastern Punta Corna, and were not detected in the western part.
Ferroskutterudite is abundant in several mining sites, and shows variable Co contents, up to 13.51 wt.%.
Safflorite and clinosafflorite (Co up to 16.26 wt.%) are less abundant and were detected only in the San
Giovanni mine.
Sb and Bi minerals are widespread in all Punta Corna. Tetrahedrite shows variable Sb contents, up to 30.24
wt.%. Bi partially replaces Sb in the tetrahedrite structure. Bi-tetrahedrite has Sb contents up to 17.33 wt.% and
Bi contents up to 15.54 wt.%. Bournonite is not as widespread as tetrahedrite, and was found only in the Santa
Barbara mine. Pyrargyrite is rare and limited to the Speranza mining site. Bi-rich varieties of chalcostibite (Sb
up to 47.27 wt.%, Bi up to 16.23 wt.%), and a Sb-Bi alloy were detected only in the Carlo Emanuele mining
site.
Sb and Bi-bearing phases are lollingite, arsenopyrite and gersdorffite. A mineral approaching lollingite
stoichiometry shows variable As substitution by Sb (Sb up to 8.72 wt.%). Arsenopyrite and gersdorffite also
display Sb fluctuations, with contents from below detection limit to 13.19 wt.%.
Finally, Co and Sb-rich secondary phases are also present in the complex. They are mostly undetermined
oxides and hydroxides with Co contents up to 10.34 wt.% and Sb contents up to 20.06 wt.%.
Tiny xenotime crystals (~10 μm) were detected at Santa Barbara and Santa Maria mining sites.
Moroni M., Rossetti P., Naitza S., Magnani L., Ruggieri G., Aquino A., Tartarotti P., Franklin A., Ferrari E., Castelli D.,
Oggiano G. & Secchi F. (2019) - Factors controlling hydrothermal nickel and cobalt mineralization - Some suggestions
from historical ore deposits in Italy. Minerals, 9(7), 429
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
- …
