1,721,001 research outputs found
Crystallographic procedures in the study of experimental rocks: x-ray single-crystal structure refinement of C2/c clinopyroxene from lunar 74275 high-pressure experimental basalt
No full textThe possibility of applying X-ray single crystal techniques to minerals pertaining to rocks experimentally crystallized in laboratory has been investigated as a new approach to precisely relate crystal-chemistry to pressure, temperature, fO2, and composition of the magma from which the crystal formed.
A clinopyroxene from the experimental lunar basalt (74275 composition) ofGreen et al. (1975) crystallized at 12 Kb and 1320 °C, was successfully refined to an R factor of 0.041. Its structure configuration turned out to be exceptional, expecially in relation to the record low Ca(M2) occupancy (0.57 atoms per formula unit henceforth a.f.u.), but comparable with the other lunar C2/c clinopyroxene previously studied with X-ray single crystal methodology: augite 12052 (Takeda 1972 a). Comparative analysis of the two lunar clinopyroxene structures revealed their common high temperature origin and the high-pressure imprint of the experimental specimen relative to the natural one.
Both lunar samples differ radically from the studied terrestrial clinopyroxenes of C2/c diopside-like structure: the main difference of lunar clinopyroxenes with respect to terrestrial analogues is the high Ally (T) (AlIV > 0.20 a.f.u.) in spite of low Ca(M2). Relative to the ideal diopside structure, Si4+ AlIV and Ca Mg + Fe2+ substitutions in T and M2 sites, respectively, turned out to be not compatible with terrestrial clinopyroxenes.
Die Anwendung von Einkristallverfahren auf Minerale aus experimentell hergestellten Gesteinen wurde untersucht; sie wird als ein neuer Weg zur quantitativen Korrelation der Kristallchemie mit Druck, Temperatur, fO2 und der Zusammensetzung des Magmas, aus dem der Kristall gebildet wurde, gesehen.
Die Struktur eines Klinopyroxens aus dem experimentellen Mond-Basalt (Zusammensetzung 74275) vonGreen et al. (1975), der bei 1320 °C kristallisierte, wurde mit Erfolg bis auf einen R-Faktor von 0.041 verfeinert. Es zeigte sich, daß seine Struktur-Konfiguration außergewöhnlich war, besonders im Hinblick auf die besonders niedrige Ca(M2) Besetzungsdichte (0.57 Atome pro Formeleinheit). Sie ist jedoch vergleichbar mit dem anderen lunaren C2/c Klinopyroxen der bisher mit Röntgen-Einkristallverfahren untersucht wurde, nämlich Augit 12052) (Takeda, 1972a). Vergleichsanalysen der beiden lunaren Klinopyroxen-Strukturen lassen ihre gemeinsame Hochtemperatur-Entstehung erkennen, sowie den — im Gegensatz zu der natürlichen Probe — deutlichen Einfluß hoher Drucke auf die experimentell hergestellte Probe.
Beide lunare Proben unterscheiden sich deutlich von den untersuchten terrestrischen Klinopyroxenen mit Diopsid-artiger C2/c Struktur: der Hauptunterschied zwischen lunaren Klinopyroxenen und ihren terrestrischen Analogen ist der hohe AlIV (T) (AlIV > 0.20 a.f.u.) trotz niedrigem Ca(M2). Im Vergleich mit der idealen Diopsidstruktur zeigte sich daß, Si4+ AlIV und Ca Mg + Fe2+ Substitutionen an T resp. M2 Plätzen nicht kompatibel mit terrestrischen Klinopyroxenen sind
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
- …
