1,723,223 research outputs found
CIL X, 7533: l'iscrizione di Antioco
No full textNel contributo viene analizzata l'iscrizione CIL X,7533 proveniente da Sulci (Sant'Antioco) e viene proposta una nuova interpretazione del testo
The sulfur budget and sulfur isotopic composition of Martian regolith breccia NWA 7533
No full textInternational audienceThe sulfur isotope budget of Martian regolith breccia (NWA 7533) has been addressed from conventional fluorination bulk rock analyses and ion microprobe in situ analyses. The bulk rock analyses yield 865 ± 50 ppm S in agreement with LA‐ICP‐MS analyses. These new data support previous estimates of 80% S loss resulting from terrestrial weathering of NWA 7533 pyrite. Pyrite is by far the major S host. Apatite and Fe oxyhydroxides are negligible S carriers, as are the few tiny igneous pyrrhotite–pentlandite sulfide grains included in lithic clasts so far identified. A small nonzero Δ33S (−0.029 ± 0.010‰) signal is clearly resolved at the 2σ level in the bulk rock analyses, coupled with negative CDT‐normalized δ34S (−2.54 ± 0.10‰), and near‐zero Δ36S (0.002 ± 0.09‰). In situ analyses also yield negative Δ33S values (−0.05 to −0.30‰) with only a few positive Δ33S up to +0.38‰. The slight discrepancy compared to the bulk rock results is attributed to a possible sampling bias. The occurrence of mass‐independent fractionation (MIF) supports a model of NWA 7533 pyrite formation from surface sulfur that experienced photochemical reaction(s). The driving force that recycled crustal S in NWA 7533 lithologies—magmatic intrusions or impact‐induced heat—is presently unclear. However, in situ analyses also gave negative δ34S values (+1 to −5.8‰). Such negative values in the hydrothermal setting of NWA 7533 are reflective of hydrothermal sulfides precipitated from H2S/HS‐ aqueous fluid produced via open‐system thermochemical reduction of sulfates at high temperatures (>300 °C)
Hydrothermal Alteration of Martian Zircons in NWA 7034/7533
Get PDFThe martian regolith breccia NWA 7034/7533
contains abundant zircon grains, which can provide insight into
crustal processes through isotopic compositions. For example, insitu
U-Pb measurements on these zircons suggest a crystallization
age of ~4.4 Ga with resetting at 1.5-1.7 Ga [1-3]. On the basis of
intragrain and intergrain oxygen isotope variations, Nemchin et
al. [4] proposed that zircons crystallized from melts that had assimilated
^(17)O-enriched regolith, and that the metamict zircons
were later altered by low-temperature fluids near the surface at
~1.7 Ga. Here, we describe the textural context of zircons in
NWA 7034 and 7533, with an emphasis on those aspects touching
on their hydrothermal alteration
The Age and Composition of the Martian Crust from NWA 7533
No full textNWA 7533 is a pre-Noachian regolith breccia, containing siderophiles consistent with 5% chondritic impactor, 4.44 Ga zircons, and LILE enrichments implying a crustal thickness of 50 km established in the first 100 Ma of martian history
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Practical Studies in E-Government: Best Practices from Around the World
No full texthttp://dx.doi.org/10.1007/978-1-4419-7533-1info:eu-repo/semantics/publishe
Variations on the Author
Get PDF“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
Get PDFWe 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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