1,721,137 research outputs found
La carne d'Europa. Benedetto Croce recensice "La carne, la morte e il diavolo" di Mario Praz
No full textSingle-Atom Catalysts for the Electro-Reduction of CO2 to Syngas with a Tunable CO/H2 Ratio: A Review
No full textNowadays, transition towards green chemistry is becoming imperative. In this scenario, an attractive perspective consists in the generation of CO through the electrochemical reduction of CO2 under ambient conditions. This approach allows storage of the electrical energy from intermittent renewable sources in the form of chemical bonds, and simultaneously reduces greenhouse gas emissions, giving carbon a second chance of life. However, most catalysts adopted for this process, i.e., noble metal-based nanoparticles, still have several issues (high costs, low current densities, high overpotentials), and in the view of generating syngas through co-electrolysis of H2O and CO2, do not enable a widely tunable CO/H-2 ratio. Single-atom catalysts with N-doped carbon supports have been recently introduced to face these challenges. The following review aims to answer the demand for an extended and exhaustive analysis of the metal single-atom catalysts thus far explored for the electro-reduction of CO2 in aqueous electrolyte solution. Moreover, focus will be placed on the objective of generating a syngas with a tunable CO/H-2 ratio. Eventually, the advantages of single-atom catalysts over their noble metal-based nano-sized counterparts will be identified along with future perspectives, also in the view of a rapid and feasible scaling-up
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
Novel Pt-Ni/NiO/Ni2O3 based electrodes for electrocatalytic biodiesel production from waste palm oil
No full textHere, the synthesis, using a simple and easy-scalable procedure, of a Pt-Ni/NiO/Ni2O3 nano-structured catalyst for the electro-assisted production of biodiesel from methanol and waste cooking palm oil is reported. After synthesis, the as-obtained nanomaterial was broadly characterized: TEM images, showed the existence of a nanohybrid with a quasi-spherical morphology consisting of platinum nanoparticles (2-3 nm) anchored to Ni/NiO/Ni2O3 nanoparticles (50 nm); XRD, TG, DTG, Raman and FT-IR analyses confirmed the obtained result.Afterward, the nanohybrid was tested for the electro-production of biodiesel at a low voltage value (10 V) and at low temperature (40 degrees C). The transesterification reaction efficiently occurred with a reduced amount of nanocatalyst in a two-phase system under strong magnetic agitation and without adopting toxic co-solvents. The effects of the reaction time, NaCl content and methanol/oil molar ratio on the methyl esters yield were studied, and the reaction products were analysed. In particular, it was observed that by using a waste palm oil treated for 7 days at 240 degrees C as feedstock, even after 60 min of reaction, a yield of >50% was reached. A yield value of similar to 96% was eventually reached after 3 h of reaction. (C) 2019 Elsevier Ltd. All rights reserved
Active and stable ruthenium/osmium based electrocatalysts for hydrogen evolution by seawater splitting
No full textActive and stable graphene supporting trimetallic alloy-based electrocatalyst for hydrogen evolution by seawater splitting
No full textThe hydrogen evolution reaction (HER), adopting seawater as an electrolyte solution, is a promising and more sustainable alternative for the production of hydrogen, yet requiring more economic, highly efficient and stable electrocatalysts than the current ones. Herein, the synthesis of a Ni, Ru, Ir-based and graphene-supported nano-structured catalyst through an easily scalable, cost-effective, surfactant-free approach has been proposed. XRD, SEM, TEM images and EDX maps showed the formation of trimetallic NiRuIr alloy nanoparticles (average diameter: 8 nm) supported on a few-layer graphene. After characterization, the HER stability and activity of the sample were tested in a 0.5 M H2SO4, in a KCl neutral solution as well as in real seawater. In the acidic electrolyte environment a 0.06 V overpotential was maintained even after 11,000 cycles and the Tafel slope recorded was very low (28 mV/dec). In the neutral solution a very low overpotential (0.10 V) and a low Tafel slope (72 mV/dec) were also obtained. Furthermore, in real seawater the sample exhibits a Tafel slope of 48 mV/dec, maintains a low overpotential of 0.08 V for 250 cycles and a constant current density for 200 h of test without significant losses and with almost a 100% hydrogen production efficiency. The results obtained proved the remarkable HER performance of the synthesized electrocatalyst, especially in real seawater in virtue of synergistic alloying effects and the presence of the graphene support
Controlled PtIr nanoalloy as an electro-oxidation platform for methanol reaction and ammonia detection
No full textHerein, a surfactant-free, ethylene glycol-mediated synthesis of PtIr nanoalloys was optimized. In particular, a post-synthesis treatment was identified as the key step in order to determine the nanoparticles size and their organization in the nanostructure, depending on the presence of a reducing agent and on pressure conditions. After synthesis, the as-obtained nanomaterials were broadly characterized: SEM and TEM images, EDX maps and XRD spectra showed the formation of nanorods with a few nanometers size and similar quantitative compositions of platinum and iridium. Afterward, the electrocatalytic activity towards the methanol oxidation reaction of the synthesized nanomaterials was tested and the best sample, treated under a hydrogen/nitrogen flow at 10 bar, exhibits a negligible onset potential (0.058 V) and a very high If/Ib ratio (2.5). Moreover, the aforementioned sample was tested as an electrochemical sensor for the detection of small traces of ammonia in an aqueous solution with a limit of detection of 4.88 μM. The sensor was tested also in simulated wastewater coming from the fertilizer industry, showing proper operation and excellent selectivity
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
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