1,720,993 research outputs found
Water in minerals of the continental lithospheric mantle and overlying lower crust: A comparative study of peridotite and granulite xenoliths from the North China Craton
No full textWater contents of clinopyroxene, orthopyroxene and olivine in mantle peridotite xenoliths from the Hannuoba and Nushan basaltic volcanoes (North China Craton) were determined by Fourier transform infrared spectroscopy (FTIR). Results show that contents vary from 50 to 155 ppm (H(2)O wt.) for clinopyroxene and from 20 to 55 ppm for orthopyroxene in Hannuoba peridotites, and from 5 to 355 ppm for clinopyroxene and from 5 to 140 ppm for orthopyroxene in Nushan peridotites. Water contents in clinopyroxene and orthopyroxene define a good positive correlation with a ratio of similar to 2.1. This, together with the roughly homogeneous distribution of hydrogen from core to rim region in pyroxene grains, suggests that they have preserved the initial water content of the mantle source. By contrast olivine in these peridotites contain very little, if any, water, which were probably caused by significant loss of H during their ascent due to the faster H diffusion in olivine relative to pyroxenes and by the relatively lower water content in the mantle source of Hannuoba and Nushan. Previous studies [Xia, Q.K., Yang, X.Z., Deloule, E., Sheng, Y.M., Hao, Y.T., 2006. Water in the lower crustal granulite xenoliths from Nushan, eastern China. journal of Geophysical Research, 111(B11202) doi: 10.1029/2006JB004296; Yang, XZ, Deloule, E., Xia, Q.K., Fan, Q.C., Feng, M., in press. Water contrast between Precambrian and Phanerozoic continental lower crust of eastern China.Journal of Geophysical Research doi:10.1029/2007JB005541] have shown that the water content ranges from 275 to 720 pprn for clinopyroxene, from 60 to 185 pprn for orthopyroxene and from 65 to 205 ppm for plagioclase in Hannuoba mafic granulite xenoliths, and from 200 to 2330 ppm for clinopyroxene, from 140 to 1270 pprn for orthopyroxene and from 145 to 900 pprn in plagioclase in Nushan maficgranulite xenoliths.The significant difference between the water content of peridotite and that of coexisting mafic granulite xenoliths, e.g. 0-100 ppm (mostly 200 ppm) for the estimated bulk concentration, demonstrates that the distribution of water in the deep continental lithosphere is vertically heterogeneous. This may be due to the different genesis of peridotites and granulites (the residue of partial melting vs. the product of melt crystallization). Based on these water data, we define the theological structure of the lowermost crust and uppermost mantle below the Hannuoba and Nushan regions. The viscosity (strength) of the underlying shallow mantle is similar, whereas the deep crust is relatively stronger at Hannuoba and weaker at Nushan. Difference in the viscosity structure may further influence the dynamical processes between different zones in this craton. (C) 2008 Elsevier B.V. All rights reserved
H2O contents and D/H ratios of nominally anhydrous minerals from ultrahigh-pressure eclogites of the Dabie orogen, eastern China
No full textGarnet and omphacite from ultrahigh-pressure eclogites from the Dabie orogen, eastern China were investigated by Micro-FTIR. The results show that all garnet and omphacite grains contain structural water occurring as hydroxyl (OH), with H2O contents varying from 14 to 1915 ppm (H2O wt) and from 105 to 695 ppm, respectively. Within the same sample, the water contents are either homogeneous at the grain scale or vary systematically from higher in the core to lower in the rim. Low water contents at crystal rims possibly result from hydroxyl exsolution after pressure decrease upon rock exhumation. The delta D values of omphacites are between -108.4 parts per thousand and -114.2 parts per thousand, and independent of water contents. Heterogeneous water contents of garnet occur at the centimeter scale and fluid mobility during UHP metamorphism was very limited. The estimated whole-rock water content based on mineral H2O contents is between 260 and 750 ppm, thereby implying that eclogitic rocks formed during continental subduction have the potential to recycle (at least) several hundreds ppm water to mantle depths. The preserved chemical differences likely indicate that the eclogitic rocks resided at mantle conditions for a limited time span, and imply that they were exhumed shortly after subduction. The water released during decompression might represent the early-stage retrograde fluid. (c) 2007 Elsevier Ltd. All rights reserved
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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