1,720,956 research outputs found
Structural and Microstructural Characterization of Zirconium Phosphates Prepared by Mechanochemical Synthesis
No full textLayered α-type zirconium phosphate (ZrP) was prepared by mechanochemical synthesis by using a planetary ball mill, in the absence of solvents. The reagents, a zirconyl organic salt and phosphoric acid (H3PO4/Zr molar ratio = 4), are mixed in an agate jar for different times, from 15 to 60 min. Additional syntheses are performed by adding oxalic acid to the reagents’ mixture. The powder samples obtained by ball milling (BM samples) are characterized by X-ray powder diffraction, thermogravimetric, scanning electron microscopy analyses, as well as31P MAS NMR and FTIR spectroscopy. Structural and microstructural parameters (unit cell parameters, unit cell volume, crystallite size, and amount of amorphous fraction) of the BM samples are compared with those of ZrP samples prepared by sol–gel and hydrothermal methods. The best results were obtained with a grinding time of 45 min, in the presence of oxalic acid (oxalic acid/Zr molar ratio = 0.2). Ball milling promotes the formation of single nanocrystals with larger unit cell parameters, especially along the layer packing direction (c axis), with respect to the ZrP samples prepared by hydrothermal synthesis, which, on the contrary, favors the formation of micrometric multidomain crystals
A Flexible, Perfluorinated Analog of Aluminum Fumarate Metal–Organic Framework
No full textHerein, we report the synthesis of Al-TFS, a novel aluminum metal–organic framework (MOF) based on tetrafluorosuccinic acid (H2TFS), of formula Al(OH)(TFS)·1.5H2O, introducing a new member to the family of perfluorinated MOFs. The structure of the MOF, solved ab-initio from laboratory powder X-ray diffraction data, displays analogies with that of the commercially available Al-fumarate (Basolite A520). The structure is composed of 1D infinite OH-bridged AlO6 octahedra chains connected by the dicarboxylic linkers, designing rhombic channels decorated by fluorine atoms. Upon water removal, the MOF undergoes a phase transition leading to a moderate expansion of the unit cell. Volumetric analysis revealed the presence of ultra-micropores with a size lower than 4 Å. Gas sorption measurements demonstrated for Al-TFS a slightly higher CO2 selectivity compared to N2 and CH4 than the Al-fumarate analog, with peculiar shapes of the isotherms suggesting a dynamic response of the framework to CO2 adsorption. Using different complementary techniques (in situ infrared spectroscopy, powder X-ray diffraction, solid-state nuclear magnetic resonance spectroscopy, gas/vapor sorption), and density functional theory simulations, the flexibility of the new MOF was disclosed, highlighting the significant impact of fluorination in tailoring materials with structural flexibility and peculiar adsorption properties
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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