1,720,964 research outputs found
Commentary on Constraints on the Equations of State of stiff anisotropic minerals: Rutile, and the implications for rutile elastic barometry [Miner. Mag. 83 (2019) pp. 339-347]
No full textThe conclusion of Zaffiro et al. (2019; Constraints on the Equations of State of stiff anisotropic minerals: rutile, and the implications for rutile elastic barometry. Mineralogical Magazine, 83, 339-347) that the Mie-Grüneisen-Debye (MGD) Equation of State (EoS) cannot fit the available data for rutile is shown to be incorrect, even though rutile exhibits significant anisotropic thermal pressure which invalidates the quasi-harmonic approximation used as the basis for the MGD EoS. The refined parameters for the MGD EoS of rutile are: KTR0= 205.05(25) GPa, = 7.2(5), θD = 399(20) K, γ0= 1.40(2) and q = 1.5(7). This EoS predicts volumes, bulk moduli and volume thermal expansion coefficients for rutile at metamorphic conditions that are statistically indistinguishable from those predicted by the 'isothermal' type of EoS reported previously
An experimental study of the replacement of leucite by analcime
No full textLeucite and analcime have open framework aluminosilicate structures, where ion exchange by cation substitution has been previously used to explain the replacement of one phase by another. Using O-18-enriched NaCl solutions in hydrothermal reactions and run-product analyses using scanning electron microscopy, infrared and Raman spectroscopy, and time-of-flight secondary ion mass spectrometry, we show that the replacement of leucite by analcime is not a solid-state reaction involving cation exchange by volume diffusion. Textural features such as nano-pores and clusters, as well as the detection of high amounts of O-18 in the framework of analcime, suggest that the reaction proceeds by dissolution of leucite and reprecipitation of analcime, where structural O atoms of the leucite framework are exchanged and a new analcime structure forms at a moving interface through the leucite parent crystal. The characteristic high porosity (on a nano-scale) in the analcime product phase results from some of the parent phase being lost to the solution to give a volume deficit reaction. However, external dimensions are maintained during the process to result in the pseudomorphic replacement of an open framework aluminosilicate structure by a coupled dissolution-reprecipitation mechanism
Phasenpetrologische Untersuchungen im System Lazulith-Scorzalith
Full text linkDie p,T-Stabilität der Mischkristallreihe Lazulith-Scorzalith (MgAl2(OH)2(PO4)2 -FeAl2(OH)2(PO4)2 ist von großem Interesse, da natürliche Lazulithe potentielle Indexminerale für die Geothermometrie und -barometrie für die Bildungsbedingungen metamorpher Gesteine sind. Hierfür wurde der thermodynamische Datensatz für dieses System bei einer fest eingestellten Sauerstofffugazität (QFI-Puffer) durch Hydrothermalexperimente vervollständigt. Lazulith, Scorzalith und ihre Mischkristalle zerfallen zu Mischkristallen des Systems (Mg,Fe)Al(PO4)O sowie Berlinit und H2O. Aus der Lage der Stabilitätsgrenzen des von diesen vier Phasen gebildeten Feldes wurden die Reaktionsenthalpien und die Reaktionsentropien sowohl der Zerfallsreaktion des Lazuliths als auch der des Scorzaliths extrahiert, und auch deren Wechselwirkungsparameter bestimmt. Bei der Untersuchung der kristallchemischen Eigenschaften ergab sich für beide Mischkristallreihen ein ideales Mischungsverhalten bezüglich ihrer Molvolumina. Hinweise auf Mischungslücken wurden nicht gefunden. Die Zellparameter der Lazulith-Scorzalith-Mischkristallreihe zeigen ein nicht lineares Verhalten, was auf eine Änderung des Substitutionsmechanismus hindeutet, der als eine oxidative Entwässerung beschrieben werden kann. Bei Hochdruckuntersuchungen zeigten weder Lazulith noch Scorzalith eine Phasenumwandlung oder einen Zerfall. Die (Mg,Fe)Al(PO4)O-Mischkristallreihe weist dagegen eine Phasenumwandlung auf. Dabei geht beta’’-FeAl(PO4)O in seine Hochdruckmodifikation alpha’-FeAl(PO4)O über, die wahrscheinlich isotyp zu der des Mg-Endgliedes ist. Ergänzend wurden Kompressibilität und thermische Ausdehnung für die beiden Mischkristallreihen bestimmt
Experimentelle Untersuchungen zur Stabilitaet, Kristallchemie und Kristallphysik von CuS_2-FeS_2-Mischkristallen
No full textSIGLEAvailable from TIB Hannover: DW 5920 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
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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