1,720,958 research outputs found
In situ analysis of white marble from the Mediterranean Basin by LA-ICP-MS: inferences on provenace based on trace-element profiles
Full text linkWhite marble is a carbonate dominant metamorphic crystalline rock used for more than 5000 years (late Neolithic – Cycladic civilizations) for statuary and architectural elements. The remarkable value taken on during the history is proved by the large and continuous use of this rock in the ancient societies.
So far, numerous studies have set out to determine the provenance of white marble exploited from the main quarrying sites of the Mediterranean basins. These studies led a large number of data, which are partial and not always satisfactory from a scientific point of view.
Actually, white marble of archeometric interest is largely characterized through minero-petrographic studies and isotopic signatures, primarily carbon, oxygen and strontium.
A complete description of the geochemical composition, aimed at an exhaustive provenance study, is still missing.
The application of the Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) permits the measurement of a large number of trace elements. The scope is to improve the limited existing database on the trace-element profile of white marble.
The comparison of the concentration of these elements among different quarrying districts aims to identify geochemical markers as fingerprints of several white marble sites.
With these assumptions, one can start to go deeper into the problem, surveying all the bibliography, the state of the art and general knowledge about this rock, i.e., its history, geology, geochemistry and archaeometry.
The specimens considered come from a collection of white marbles chips, collected from the past sampling campaigns of La Sapienza University of Rome and IGAG-CNR of Rome, and largely analyzed by means of several analytical techniques in previous research works (i.e., stable isotope concentrations, EPR intensities, petrographic observations).
The sampling is composed of about 120 white marble samples from nine different quarrying areas (i.e., Carrara, Paros, Penteli, Afyon, Göktepe, Naxos, Thasos, Thiountas and Proconnesos) and eight archeological samples of known attribution to test the feasibility of the method.
This Ph.D. thesis is based on a multi-analytical approach and it can be divided in two phases. The first one consists of a systematic minero-petrographic characterization of a selection of the geological white marbles of known provenances, in order to identify the occurrence of minero-chemical markers discriminating different quarrying districts.
The second step provided analyses on rock samples from different quarries of the Mediterranean area and archeological samples from the Casa di Augusto (Palatine Hill) and Musei Capitolini collection by means the LA-ICP-MS. The analyses have been conducted at the Laboratory of Inorganic Chemistry of Eidgenössische Technische Hochschule (ETH) of Zurich and at the laboratory of CNR-Istituto di Geoscienze e Georisorse, U.O.S. of Pavia.
The goal of this study is to fulfill a database, gathering the more significant features of the proposed minero-petrographic and geochemical markers. The multidisciplinary collaboration among the different competences (geologists, chemists, conservation scientists) is fundamental to carry out this study, and this mutual collaboration is an integral part of the present Ph.D. thesis.
Going in more detail into the structure of the work, the present thesis provides: 1) an overview on the use of white marble throughout the centuries and civilizations, and the state of the art about previous studies of provenance focused on white marble; 2) the description of the geological settings of the areas where the white marble considered were sampled, presenting also the history of the main quarries; 3) a brief description of the geological samples here analyzed and the experimental setup employed; 4) the results on the quarried samples; 5-6) a discussion and conclusion, with some proposals for future improvements. Finally, in the Appendix are presented the geochemical results of archeological samples
Redox state of subcontinental lithospheric mantle and relationships with metasomatism: Insights from spinel peridotites from northern Victoria Land (Antarctica)
No full textRift-related Cenozoic alkaline mafic lavas from northern Victoria Land (Antarctica) carry abundant mantle xenoliths whose oxygen fugacities (fO2) were determined to assess how the metasomatism, related to Cenozoic magmatism, affected the state of oxidation of the lithospheric mantle. The xenoliths used for this study are anhydrous spinel peridotites sampled in two localities, Greene Point and Baker Rocks, that show different extents of metasomatism: these are limited to incompatible element enrichments in Greene Point and to enrichments in major, minor and trace elements at Baker Rocks. The data set includes a composite xenolith from Baker Rocks, formed by a depleted lherzolite crosscut by an amphibole-bearing vein. Mössbauer spectroscopy was used to accurately determine the Fe3+/Fetot ratios in spinel and amphibole minerals. Amphiboles were also characterized by Single-Crystal X-ray Diffraction, and the crystallographic data were used to calculate the dehydrogenation. The oxidation state recorded by the xenoliths ranges from 0. 2 to 1. 5 log-bar units below the fayalite-magnetite-quartz (FMQ) buffer (ΔlogfO2) with the highest values observed in the metasomatized samples from Greene Point. For the vein of composite Baker Rocks xenolith, Δlog fO2 was estimated on the basis of the amphibole in -1. 7 log-bar units, a value close to those calculated for all Baker Rocks xenoliths (ΔlogfO2 = -1. 5 to -1. 1 log-bar units). These results indicate a similar oxidation state for lithospheric mantle prior to the metasomatic event at Greene Point and Baker Rocks (ΔlogfO2 ~ -1. 3 log-bar units). Metasomatism produced different effects in the shallow mantle at the two sites. At Greene Point, an oxidizing metasomatic melt caused the rise of fO2 in peridotite portions close to melt conduits up to FMQ. In contrast, at Baker Rocks, a metasomatizing melt with fO2 similar to that of the peridotite matrix produced chemical changes in the surrounding mantle rocks and amphibole crystallization without significantly modifying the local oxidation state. The origin of such different metasomatic melts, as well as the variety of primary magmas produced during the magmatic phase of Cenozoic rifting, is linked to the geodynamic evolution of the rift and probably involved the melting of a heterogeneous mantle source composed of a peridotite veined by pyroxene-bearing veins formed from an earlier amagmatic phase of the rift. © 2012 Springer-Verlag
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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