1,721,004 research outputs found
Chemical reactivity of pozzolans from Sardinia for the production of hydraulic limes
No full textThe research is aimed at studying the chemical reactivity between lime and volcanic rocks belonging to different Sardinian outcrops, for a use as raw material in the production of hydraulic / pozzolanic limes. On the basis of preliminary geochemical and mineralogical-petrographic investigations, several volcanic rocks with a basic-intermediate to acid composition (substantially from andesitic, to dacitic, to rhyolitic) have been selected and used for to perform laboratory reactivity tests. These rocks differ in the variable content of glass (from 15% to about 95% in volume), due to the presence of secondary minerals, and to physical characteristics (density, porosity, water absorption, etc.). The physical properties are essentially linked to the different compositional incidence of the crystalline, crystal-clastic, lithic (present in some pyroclastic facies), type and quantity of glass phases, to their different methods of installation (conditioned by temperature, chemical composition, grade welding, etc.), and to the different degree of alteration.
The results of the investigations on the pozzolan materials (by polarized light microscopy, XRD, SEM, EPMA-WDS, Chapelle test) show that following parameters affect the chemical reactivity of the volcanic products with lime: i) quantity and type of amorphous phases (glass), linked to the different emplacement of volcanic rocks (affected by temperature, chemical composition, welding grade, etc.), ii) compositional incidence of the crystalline phases, crystal-clasts, lithics (these latter present in some pyroclastic facies), iii) alteration grade of the rocks and presence of secondary minerals (e.g., zeolites, phyllosilicates, etc.)
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
HIGH-PRESSURE BEHAVIOR OF MICROPOROUS MATERIALS: CRYSTAL-FLUID INTERACTIONS AND DEFORMATION MECHANISMS AT THE ATOMIC SCALE
Full text linkZeolite are crystalline, hydrated aluminosilicates characterized by a tetrahedral framework of TO4 units connected in such a way that sub-nanometric channels and cages occur. These structural cavities host the so-called extra-framework population, which mainly consists of alkali and alkaline-earth cations and small molecules, such as H2O. In the last decades, the scientific community showed a rising interest on the behavior of microporous and mesoporous compounds (e.g., zeolites) at high-pressure conditions, and in particular on the crystal-fluid interaction phenomena occurring at extreme conditions. As zeolites could act as an ideal carrier of H2O and others small molecules or monoatomic species (e.g., CO2, CH4, H2S, He, Ar, Kr, Xe,...), experiments on zeolites compressed (and ambient to low/high T) in aqueous mixtures have important implications in the Earth Sciences. Furthermore, high-pressure experiments on synthetic zeolites may pave the way for new routes of tailoring new functional materials (made by hybrid host-guest architecture), bearing a potentially relevant technological impact. In this experimental thesis, after an overall introduction and a section on the high-pressure experimental techniques (Chapter 1 and 2 , respectively), the high-pressure behavior and the crystal-fluid interaction at the atomic scale of a selected series of natural and synthetic zeolites (i.e., AlPO4-5, leonhardite, laumontite, phillipsite) and a zeolites-like mineral (i.e., armstrongite) have been investigated by means of in-situ single-crystal X-ray diffraction, using “penetrating” and “non-penetrating” pressure-transmitting fluids. Into details:
1. AlPO4-5 (Chapter 3): the high-pressure behavior of AlPO4-5 has been studied by single crystal XRD using synchrotron radiation and a diamond anvil cell (DAC), with crystals compressed in silicone oil and methanol:ethanol:water =16:3:1 (m.e.w.) mixture. The high-pressure evolution of the crystalline structure and the deformation mechanism at atomic scale have been described on the basis of high-quality structure refinements, revealing adsorption phenomena of H2O (and likely methanol) already at 2 Kbar. Moreover, evidence of an incommensurately modulated structure of AlPO4-5 have been found.
2. Leonhardite and laumontite (Chapter 4): the H2O adsorption kinetics, at ambient pressure and temperature, of leonhardite to give laumontite has been investigated using single crystal XRD techniques. In-situ high-pressure XRD experiments, using synchrotron radiation and a DAC, have been performed in order to obtain the bulk moduli of the two minerals (previously unknown). A detailed description of the atomic deformation mechanisms has been addressed.
3. Phillipsite (Chapter 5): the pressure-induced deformation mechanisms, at the atomic scale, have been studied via single crystals XRD-experiments, using synchrotron radiation and a DAC. Despite no pressure-induced adsorption was observed, the experimental findings suggest a change in the deformation mechanisms induced by a re-arrangement of the extra-framework population.
4. Armstrongite (Chapter 6): the high-pressure evolution of this zeolite-like mineral has been studied in the m.e.w. as nominally penetrating fluid. A first-order phase transition has been detected between 4 and 5 GPa.
In the Chapter 7 a detailed discussion of the aforementioned experimental findings has been addressed, along with their technological and geological implications. The results of the present studies have been published in peer-reviewed journals
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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