1,721,458 research outputs found
Notes about the painting techniques and the morphological, chemical and structural characterization of the writing surface of the prehispanic mexican codex cospi
No full textLaurencich Minelli Laura, Gasparotto Giorgio, Valdrè Giovanni. Notes about the painting techniques and the morphological, chemical and structural characterization of the writing surface of the prehispanic mexican codex cospi. In: Journal de la Société des Américanistes. Tome 79, 1993. pp. 203-207
Microbial geomorphologies in modern salt flats and their astrobiological significance
No full textFollowing the discovery of Martian mineral deposits with an assumed evaporite origin (especially sulfates), salt flat areas from hot and cold arid environments (such as sabkhas and playa lakes) are currently investigated for comparative analysis between terrestrial salt-bearing settings and their Martian environmental analogs. Similarly to the Earth, evaporite deposits seem widespread on Mars where their stratigraphic setting and composition suggest relationships with aqueous environments and, therefore, they represent a useful indicator of habitability.
Among the traces of biological activity retained in salt flat settings those produced by surface to near surface microbial activity deserve a special astrobiological interest. These microbial geomorphologies derive from the interaction between physical and biological agents, and can impact on the development and stabilization of surface morphologies with some fossilization potential. Therefore, once established a clear relationship between micro-geomorphologies and micro-biota, their recognition at the surface on Martian terrains may represent unambiguous indicators of biogenicity.
In the sabkha Oum Dba, near the Atlantic coast of the Western Sahara (southern Morocco), thick microbial mats and mineral precipitations (carbonates and sulfates) are in progress and actively interact in an ecosystem where living and fossilized sectors coexist. It, therefore, represents an ideal natural site for detecting type, evolution, and stabilization of microbial geomorphologies in a typical arid salt flat area
La ceramica etrusca a vernice nera di Valle Trebba: dati archeologici e archeometrici a confronto
No full textIl contributo si prefigge di affrontare da un punto di vista archeologico e archeometriche alcune delle problematiche relative allo studio delle ceramiche a vernice nera di produzione etrusca della necropoli di Valle Trebba della città etrusca di Spina. Nella prospettiva archeologica, viene presa in rassegna criticamente la bibliografia di riferimento e si approfondisce la problematica delle ciotole, una forma ceramica molto diffusa e dalla lunga vita produttiva dal tardo-arcaismo fino al III sec. a.C. Nella prospettiva archeometrica, si discutono i risultati delle analisi di un consistente gruppo di individui ceramici selezionati, arrivando alla identificazione di differenti tecniche di produzione nelle ceramiche locali e al riconoscimento di una produzione già di V sec. a.C
Eclogites, jades and other HP-metaophiolites employed for prehistoric polished stone implements in Italy and Europe
Full text linkPrehistoric polished stone tools are now fairly well-known from a petrographic point of view in Northern Italy. Many more than one thousand implements sampled from the most important sites and collections (axes, adzes, chisels, some ornaments and various tools fragments), have been analysed. These artefacts were commonly employed from the Neolithic period onwards for working wood and cutting the forest trees. Surface optical observations, density, thin sections, XRD, microprobe analyses and bulk chemistry have been employed, alone or in combination, for petrographic study oriented to archaeometric interpretation. Alpine eclogites, jades (Na-pyroxenites) and other minor HP (High Pressure) metaophiolites dominate the polished stone lithology of Northern Italy, being at least 70% and often surpassing 90% of stone materials in single sites. Petrographic, geochemical, minerochemical, textural data of the studied rocks are described and discussed in some detail. A number of new definitions are introduced. The provenance of the raw material is identified as being NW Italy, essentially Piedmont and Liguria. These regions represent one of the few geological zones in the world where alpine eclogites and jades occur, both as primary outcrops in the High Alps, alluvial and morainic deposits along the valleys, and Oligocene conglomerates in the Northwestern Apennines. The dominance of eclogites and jades among the prehistoric polished stone tools represents a lithic selection of cultural significance. This selection seems to be justified by litho-technological (best mix of hardness, toughness and density) and aesthetic (fine green colours, translucency) reasons, which caused the exclusion of other, elsewhere common, lithologies. The remarkable presence of jade and alpine eclogite lithologies among the Western and rarely Central European axe blades (mostly status symbol or ceremonial axes) gives evidence of a relevant long distance exportation of HP metaophiolite materials from NW Italy to France, Germany, Benelux, Great Britain, etc., up to1000-1500 km far from the source areas. The still unsystematic petrographic knowledge of the HP-metaophiolitic stones of the axe blades in Europe, as well as in the Italian Peninsula, allows only a preliminary comparison with the better known Northern Italian implements
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
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