1,721,180 research outputs found
Methodology for the investigation of surfactant dissolution in water
No full textConcentrated aqueous solutions of surfactants pastes are widely used in industrial productions. The dissolution phenomena of these fluids in water is difficult to optimize, given the thermodynamic complexity of the system, that adds further resistance to the mass transport efficiency. One of the most common anionic surfactants is Sodium Lauryl Ether Sulphate (SLE3S). Depending on the SLE3S-water composition, surfactant nano-molecules can assume different morphologies, such as micellar phases (30%wt), cubic structures (~60%wt), or lamellar liquid crystals (>60%wt), which are characterized by nanoscale ordered structures. Different phases show strongly different rheological behaviour. All phases are non-Newtonian, with a shear-thinning viscosity as function of imposed shear rate. A novel methodology is here proposed to investigate the dynamic evolution of the phase changes during surfactant dissolution using Time-lapse microscopy. Samples are observed trough crossed polarizers. Differences in nano-morphology, due to molecules rearrangement during phase changes, can be easily monitored by measuring light intensity profiles
SLE3S-water system: a linear rheological characterisation
No full textSurfactant-water mixtures display a complex rheological behaviour, with changes in parameters such as viscosity and moduli of several orders of magnitude as a consequence of phase changes, depending on their concentration and temperature: this criticism heavily affects different industrial processes. In our work, linear rheological behaviour of aqueous mixtures of a commercial anionic surfactant, sodium lauryl ether sulphate, is investigated in a range of temperature (30-60 ?) and surfactant concentration (20-72%wt) of technological relevance. Four phases with different texture are identified by polarised light microscopy: micellar, hexagonal, cubic and lamellar, all showing a shear-thinning behaviour. Rheological parameters of cubic phase show a net jump in a relatively narrow temperature range, suggesting a temperature-induced phase change. The systematic analysis of the rheological behaviour of this widely used surfactant system, reported here for the first time, can be of fundamental support for many industrial applications
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
Size-confinement of CsH2PO4 in anodic alumina membranes for thin film electrolyte solid acid fuel cell
No full textAdvances in anodic alumina membranes thin film fuel cell: CsH2PO4 pore-filler as proton conductor at room temperature
No full textAnodic alumina membranes (AAM) filled with cesium hydrogen phosphate proton conductor have been tested as inorganic composite electrolyte for hydrogen-oxygen thin film (≤50 μm) fuel cell (TFFC) working at low temperatures (25 °C), low humidity (Tgas = 25 °C) and low Pt loading (1 mg cm-2). Single module TFFC delivering a peak power of around 15-27 mW cm-2, with open circuit voltage (OCV) of about 0.9 V and short circuit current density in the range 80-160 mA cm-2 have been fabricated. At variance with pure solid acid electrolytes showing reproducibility problems due to the scarce mechanical resistance, the presence of porous alumina support allowed to replicate similar fuel cell performances over numerous AAM/CsH2PO4 assemblies. A scale-up process of the electrodic area has been optimized in order to increase the delivered peak power of AAM thin film fuel cell. Morphological, chemical and electrochemical studies on the alumina composite electrolyte have been carried out by means of scanning electron microscopy, X-ray diffractometry, Micro-Raman spectroscopy, DTA/DTG analysis, ac impedance spectroscopy and single fuel cell tests
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