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Fassinaite, Pb(2)(2+)(S(2)O(3))(CO(3)), the first mineral with coexisting thiosulphate and carbonate groups: description and crystal structure
No full textThermessaite-(NH4), (NH4)2AlF3(SO4), a new fumarole mineral from la Fossa crater at Vulcano, Aeolian Islands, Italy
Full text linkThermessaite-(NH4), ideally (NH4)2AlF3(SO4), is a new mineral found as a medium- to high-temperature (about 250-300°C) fumarole encrustation at the rim of La Fossa crater, Vulcano, Aeolian Islands, Italy. The mineral deposited as aggregates of micrometer-sized sharp prismatic crystals on the surface of a pyroclastic breccia in association with thermessaite, sulfur, arcanite, mascagnite, and intermediate members of the arcanite-mascagnite series. The new mineral is colorless to white, transparent, non-fluorescent, has a vitreous luster, and a white streak. The calculated density is 2.185 g/cm3. Thermessaite-(NH4) is orthorhombic, space group Pbcn, with a = 11.3005(3) Å, b = 8.6125(3) Å, c = 6.8501(2) Å, V = 666.69(4) Å3, Z = 4. The eight strongest reflections in the X-ray powder-diffraction data [d in Å (I) (hkl)] are: 5.65 (100) (200), 4.84 (89) (111), 6.85 (74) (110), 3.06 (56) (112), 3.06 (53) (221), 3.08 (47) (311), 2.68 (28) (022), 2.78 (26) (130). The average chemical composition, determined by quantitative SEM-EDS (N by difference), is (wt%): K2O 3.38, Al2O325.35, SO336.58, F 26.12, (NH4)2O 22.47, O = F -11.00, total 102.90. The empirical chemical formula, calculated on the basis of 7 anions pfu, is [(NH4)1.85K0.15]Σ2.00Al106F2.94-S0.98O3.06. The crystal structure, determined from single-crystal X-ray diffraction data [R(F) = 0.0367], is characterized by corner-sharing AlF4O2octahedra which form [001] octahedral chains by sharing two trans fluoride atoms [Al-F2 = 1.8394(6) Å]. Non-bridging Al-F1 distances are shorter [1.756(1) Å]. The two trans oxygen atoms [Al-O = 1.920(2) Å] are from SO4tetrahedra. NH4+ions occur in layers parallel to (100) which alternate regularly with (100) layers containing ribbons of corner-sharing AlF4O2octahedra and associated SO4 groups. The NH4+ions are surrounded by five oxygen atoms and by four fluorine atoms. The mineral is named as the (NH4)-analogue of thermessaite, K2AlF3(SO4), and corresponds to an anthropogenic phase found in the burning Anna I coal dump of the Anna mine, Aachen, Germany. Both mineral and mineral name have been approved by the IMA-CNMNC commission (IMA 2011-077)
La miniera di manganese di Varenche (Aosta, Italia nord-occidentale): ardennite, arseniopleite, manganberzeliite, pirofanite, sarkinite, thortveitite, nuovo As-Sc-analogo della metavariscite e altre specie
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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
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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