1,721,485 research outputs found
Finite element analysis of electro-mechanical deflection of cantilevers for SPM and MEMS
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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
3D meso-nanostructures in cleaved and nanolithographed Mg-Al-hydroxysilicate (clinochlore): Topology, crystal-chemistry, and surface properties
No full textThe peculiar physico-chemical properties that a solid surface can present, unlike the bulk, are the key for a huge amount of important and widespread processes, including for instance, contaminant and biomolecules adsorption, solid-state and ion exchange reactions, soil aggregation, adhesion in micro and nanodevices. In this regard, the development of new materials and three-dimensional nanofabrication technologies becomes a fundamental challenge. Here, the authors present both natural and synthetic three-dimensional meso-nanostructures of a particular Mg-Al-hydroxysilicate (mineral clinochlore) produced by scanning probe microscopy related methods. Topology, crystal-chemistry, and surface properties were addressed by experimental and theoretical methodologies on nanocleaved and nanolithographed clinochlore. Scanning probe microscopy revealed a meso-nanostructured heterogeneous surface in terms of morphology, hydrophilic/phobic character and surface potential. The possibility to arbitrarily tailor and fabricate surface nanopatterns by SPM-based nanolithography is reported. Quantum mechanical simulations of the crystal-chemical structure and material properties supported and corroborated the experimental data. These findings suggest that the heterogeneous three-dimensional meso-nanostructured surface of clinochlore can represent an optimal effective substrate for exploring specific and innovative catalytic, electrochemical and biological processes at the nanoscale
Benchmarking dispersion-corrected DFT methods for the evaluation of materials with anisotropic properties: Structural, electronic, dielectric, optical and vibrational analysis of calcite (CaCO3, space group: R 3 c)
Full text linkCalcite (CaCO3, space group R3c) is a solid phase whose well-known highly anisotropic physical properties can be exploited to compare and calibrate various theoretical simulation methods. In this work, to benchmark different ab initio Density Functional Theory approaches that include for the first time corrections for dispersive forces, a systematic analysis of structural, electronic, dielectric, optical and vibrational properties of calcite is performed. The simulations considered the generalized-gradient approximation functional PBE and the hybrid B3LYP and PBE0, whereas the DFT-D2 and DFT-D3 schemes were adopted to account for the long-range interactions. This study suggests an overall better agreement between the theoretical results obtained with the DFT functionals corrected for the dispersive forces, with a better performance of hybrid functionals over PBE
Correction factors for the effect of shape and thickness of SEM-EDS microanalysis of asbestos bundles and fibres by Monte Carlo simulation
No full textSEM-EDS quantitative microanalysis of asbestos mineral fibres still represents a complex analytical issue because of the variable fibre shape and small thickness (<5 μm) compared with the penetration of the incident electron beam. Size and shape of micro- and sub-micrometric particles may cause large errors in chemical quantification due to particle effects on the generation and measurement of X-rays intensity from the sample. These effects are related to the elastic scattering of electrons in the finite size (mass) of the fibre, with the scattering being strongly influenced by the average atomic number. For a given mean atomic number, the thickness of the particle is the main factor affecting X-rays intensity, with a component related to the particle shape that biases the contributions of absorption and fluorescence to the correction routine. To overcome these issues empirical methods were developed, however they are cumbersome and need characterized standards for thickness, geometry and composition. Here we present the results of Monte Carlo investigation for the thickness and shape effects on SEM-EDS and microprobe analysis of asbestos bundles. Crocidolite, amosite, tremolite-asbestos, chrysotile, anthophyllite-asbestos and actinolite-asbestos were simulated and correction factors for X-ray microanalysis were proposed. Monte Carlo simulation was used to investigate electron transport, X-ray generation and detection in asbestos bundles of variable thickness lying on a pure carbon holder. We report the results obtained on 100 μm long bundles of fibres of square section and thicknesses from to 0.1 μm to 10 μm. Realistic experimental conditions, such as sample geometry, SEM set-up and detector physics were taken into account. An electron probe of 40 nm in diameter was simulated, focussed in parallel illumination onto the surface of the bundle of fibres, in a mid position with respect to the edges. The modelled EDS detector has a resolution of 130 eV measured at Mn Kα, an elevation angle of 40°, and an azimuthal angle of 0°. The influence of thickness and shape on the simulated spectrum was investigated for electron beam energies of 5, 15 and 25 keV. A strong influence of the asbestos bundles thickness was observed. In general, the X-ray intensities as a function of bundle thickness showed a considerable reduction below about 0.5 μm at 5 keV, 2 μm at 15 keV, and 5 μm at 25 keV, with a non-linear dependence. Specific correction parameters, k-ratio, for the asbestos bundle thickness effect are here presented
Water adsorption behaviour on (001) pyrophyllite surface from ab initio Density Functional Theory simulations
Full text linkThe present study focuses on the interaction between water and a single layer of the (001) pyrophyllite surface. Pyrophyllite [Al2Si4O10(OH)2] is an important phyllosilicate characterized by strong in-plane covalent bonds and weak van der Waals interactions holding the structural layers together. The investigation was carried out by ab initio Density Functional Theory simulations, performed both at 0 K and room conditions (300 K, 1 bar) using static and molecular dynamics approaches, respectively. The adsorption of one to three water molecules, investigated by static method, showed that the hydration is completely driven by van der Waals interactions and, as the water content increases, so does the tendency of the solvent to self-assemble. In fact, the binding energies per H2O molecule were calculated as −17.2 kJ mol−1, −11.8 kJ mol−1, and − 11.6 kJ mol−1 for the adsorption of one, two, and three water molecules, respectively. The results showed that water forms structures that resemble those typically found in the gas phase, i.e. water dimer and triangular cluster. Regarding the latter, the ab initio molecular dynamics simulations proved that this self-assembly is stable over the considered time for the run. These findings are in good agreement with the few previous data reported in the literature and could be of great use for both experimental and theoretical applications in both mineralogy and petrography and for the development of bidimensional van der Waals material from natural sources
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