1,721,049 research outputs found
Electrochemical synthesis and characterisation of polythiophene conducting polymers functionalised by metal-containing porphyrine residue
No full textTwo different copolymers of 2,2'-bitthiophene and of new thiophene derivatives, bearing in the beta position a porphyrin macrocycle, either free or complexed with Ni(II), have been electrogenerated and studied. The electrochemical behaviour of the relevant coatings has been compared, and the complexing ability of the macrocycle with respect to Ni(II) ion has been investigated. Moreover, the possibility of growing the metal-containing polymer on a micro Pt disk has been checked. The resulting modified microelectrode has been characterised and tested. (C) 2000 Elsevier Science S.A. All rights reserved
Determination of trace amounts of Eu3+ and Yb3+ ions at nafion-coated thin mercury film electrodes
No full textThe use of Nafion-coated thin mercury film electrodes (NCTMFE) for determining trace amounts of Eu3+ and Yb3+ ions was examined. Ion-exchange preconcentration of submicromolar levels of the two rare earths was achieved efficiently at a rotating NCTMFE, while the use of "classical" Nafion-coated glassy carbon electrodes is restricted to the determination of Eu3+ alone. Differential-pulse voltammetry was used to quantify the accumulated ions. The influence of variables such as rotation rate, preconcentration time and scan parameters was assessed. A preconcentration -voltammetry-regeneration scheme suitable for multiple analysis with the same modified electrode was developed. Calibration graphs with a linearity range extending up to 2 μM and detection limits of 0.03 and 0.08 μM for Eu3+ and Yb3+, respectively, were obtained. For Yb3+, the detection limit can be lowered to 0.02 μM by electrocatalytic amplification of the signals achieved by operating in the presence of ammonium nitrate as supporting electrolyte. However, in this instance a more restricted linearity range is observed. The effect of competing incorporation caused by the presence in solution of an excess of La3+ is also discussed, together with the competition between Eu3+ and Yb3+ when one of the two is present in large excess over the other. © 1991
Structure, morphology and magnetic properties of Au/Fe3O4 nanocomposites fabricated by a soft aqueous route
No full textHigh-performance size exclusion chromatography in the evaluation of molecular size distributions of humic acids fractionated by ultrafiltration
No full textThe distribution of the molecular weights in humic acid fractions are evaluated by HPL
Anionic clay modified electrode for detection of alcohols. An electrocatalytic amperometric sensor
No full textThe mechanism of the electrocatalytic oxidation towards a wide series of alcohols, by an electrode covered with the [Ni/Al-Cl] hydrotalcyte-like clay, has been analyzed in the different steps it consists of. Such a clay has been reported to be electrically conductive via a mechanism that shows similarities with that of the redox polymers. The overall process occurs in quite a complicated physical system that is completely different both from a classical electrode-solution one and from an electrode covered with a film of heterogeneous catalyst. By varying the characteristics of the substrate, in terms of steric hindrance and dipole moment of the molecule, the factors affecting the redox mediator-substrate reaction have been studied. The concentration ranges where the amperometric response varies linearly have been determined for the different substrates considered
Effect of cationic charge and hydrophobic index of cellulose-based polymers on the semipermanent dyestuff process for hair
No full textIn this work, the effects of a new class of polymers generally used in hair and skin cleansing products, the SoftCAT (SofCAT SL and SoftCAT SX), on the dye uptake on the hair fibre and the fading effects has been studied. These polymers, based on quaternary ammonium salts of hydroxyethylcellulose, are cationic products that differ in viscosity, hydrophobic substitution index (HS) and/or cationic substitution (CS, % N). UV–Vis spectroscopy has been used to analyse the extracted dyes from the hair cuticle and the cortex. The results indicate that the presence of polymers in the dye bath improve both the quality of the dyeing process and the anti-fading effect during the washing cycles. This phenomenon is postulated to be attributable to the polymers hydrophobically bonding with the dyes and so facilitating their increased penetration into the hair
A simple and industrially scalable method for making a PANI-modified cellulose touch sensor.
No full textA simple and industrially scalable method for making a PANI-modified cellulose touch sensor.
Ragazzini a, I. Gualandi a, *, S. Selli b, C. Polizzi a, M.C. Cassani a, D. Nanni a, F. Gambassi a, F. Tarterini a, D. Tonelli a, E. Scavetta a, B. Ballarin a, *
a Department of Industrial Chemistry “Toso Montanari”, Bologna University, Viale Risorgimento 4, I-40136, Bologna, Italy; b Cromatos s.r.l., via G. Cardano, 6B/C/D, 47122, Forlì, Italy
Nowadays, alternatives to the traditional electronics that should be low cost, degradable, compostable and made from environmentally nontoxic substances are of great interest in research. As candidate, we propose bare fibers of cellulose made conductive by an in situ oxidative polymerization of aniline. The resulting composite fibers were emplojed to fabricate electroactive sheets using a pilot plant of a typical paper industry. The resistivity of the obtained sheets is 14 ± 1 Ω sq-1, a value around 1000 times lower than those reported in literature. The higher electronic performances of the sheets were demonstrated by assembling a capacitive touch sensor device with optimized geometry. The touch sensor shows an increase of 3–4 % of the starting electric capacity after compression and a fast response time of 52 ms. To our knowledge this is the first time that a device is prepared in this way and therefore, the herein presented results can bring a significant improvement in the development of low-cost, green and high-tech electronic devices 1.
[1] Ragazzini, I. et al. A simple and industrially scalable method for making a PANI-modified cellulose touch sensor. Carbohydr. Polym. (2020) doi: 10.1016/j.carbpol.2020.117304
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
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