1,720,975 research outputs found
Thin Films of Plasma-Polymerized n-Hexane and ZnO Nanoparticles Co-Deposited via Atmospheric Pressure Plasma Jet
Get PDFThis study explores the co-deposition of thin polymeric films loaded with nanoparticles for its possible future application as radiation detectors. Thin films containing zinc oxide (ZnO) nanoparticles in plasma polymerized n-hexane (PPH) were deposited on silicon substrates using an atmospheric pressure plasma jet (APPJ). Crystalline ZnO nanoparticles were produced by wet chemistry, characterized, and injected through the plasma with an aerosol buffer. The precursor hydrocarbon was polymerized in atmosphere at room temperature by the plasma, resulting in a highly crosslinked structure chemically stable against common solvents. The polymer structure was characterized by FT-IR, NMR, and thermal analyses. Photoluminescence analysis revealed that ZnO UV excitonic emission is recovered owing to the passivation through polymeric encapsulation, with a remarkable increase in luminescence yield
Barium Titanate Functionalization with Organosilanes: Effect on Particle Compatibility and Permittivity in Nanocomposites
Get PDFBarium titanate (BT) recently gained new interest in the preparation of dielectric and piezoelectric lead-free materials for applications in sensors, electronics, energy harvesting and storage fields. Barium titanate nanocomposites can achieve attractive performance, provided that the compatibility between ceramic particles and polymeric matrices is enhanced to the benefit of the physical properties of the final composite. Tuning the particle–matrix interface through particle functionalization represents a viable solution. In this work, surface functionalization of BT nanoparticles (NPs), obtained by hydrothermal synthesis, with 3-glycidyloxypropyltrimethoxysilane, 2-[(acetoxy(polyethyleneoxy)propyl]triethoxysilane and triethoxysilylpropoxy(polyethyleneoxy)dodecanoate, was performed after optimizing the hydroxylation process of the NPs to improve their surface reactivity and increase the yield of grafting. Solid-state nuclear magnetic resonance and thermogravimetric analysis were used to quantify the molecules grafted onto the ceramic nanoparticles. Both bare and functionalized particles were employed in the realization of epoxy- and polydimethylsiloxane (PDMS)-based nanocomposites. Functionalization was proven to be beneficial for particle dispersibility and effective for particle alignment in the PDMS matrix. Moreover, the dielectric constant measurements revealed the potential of PDMS-based nanocomposites for applications in the field of dielectric elastomers
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
Properties of anion exchange membrane based on polyamine: Effect of functionalized silica particles prepared by sol–gel method
No full textMembranes of polyamine (PA-SiNH2)m, containing silica reacted with 3-aminopropyltriethoxysilane (APTES) in hydrolytic conditions were prepared via solution casting, followed by methylation and ion exchange process. The influence of amino-functionalized silica (Si-NH2) on the properties of the obtained membrane was investigated. Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance spectroscopy (NMR) were used to investigate the chemical features of the silica and its interaction with the polyamine polymer. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the modified membrane confirmed it is stable up to 300 °C. The thermal stability is the result of the interaction of modified silica particles and polyamine polymer. It was demonstrated that the performance of the (PA-SiNH2)m anion exchange membrane is greatly improved by incorporation of silica nanoparticles as compared with the anion exchange membrane (PK-PDAPm), which doesn't contain silica. Therefore, the (PA-SiNH2)m is a suitable candidate for electrochemical applications
Smart and Covalently Cross-Linked: Hybrid Shape Memory Materials Reinforced through Covalent Bonds by Zirconium Oxoclusters
No full textThe first examples of organic–inorganic hybrid materials reinforced by transition-metal oxoclusters that exhibit shape memory properties, based on the covalent incorporation of zirconium-based inorganic building blocks, are reported. Methacrylate-functionalized zirconium oxoclusters Zr4O2(OMc)12 and [Zr6O4(OH)4(OOCCH2CH3)3{OOCC(CH3)=CH2}9]2, with the covalent incorporation in a butyl acrylate (BA)/polycaprolactone dimethacrylate (PCLDMA) copolymer and the noncovalent incorporation of [Zr6O4(OH)4(OOCCH2CH3)12]2 are focused upon herein. Shape recovery and fixity rates are studied to observe if the shape memory properties are preserved upon going from a simple copolymer to noncovalent or covalent-based hybrids. These rates display values higher than 90 %, which provides evidence that the oxocluster does not hinder the shape memory properties in the hybrid materials. The introduction of an inorganic phase and the progressively more stable interactions between organic and inorganic parts lead to an enhancement of the thermomechanical properties. The materials are characterized through FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and swelling tests. Dynamic–mechanical analyses are used to investigate whether the hybrid materials display thermally activated shape memory properties. The stability of the hybrid materials are evaluated by a combined spectroscopic approach based on FTIR, solid-state NMR, and X-ray absorption spectroscopy
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