1,721,004 research outputs found
Catalytic wet air oxidation of D-glucose by perovskite type oxides (Fe, Co, Mn) for the synthesis of value-added chemicals
No full textThe conversion of common biomasses derived, as D-glucose, into value-added chemicals has received highest attention in the last few years. Among all processes, the catalytic wet air oxidation (CWAO) of derived biomasses using noble metal-based heterogeneous catalytic systems has been investigated. Nevertheless, the redox effect of such catalysts on such bio-compounds has still to be investigated in detail. In the present work, the activity for the conversion of D-glucose into C6 aldaric acid, lactic acid and levulinic acid of some perovskite type oxides (LaBO3; B: Fe, Co, Mn) characterized by noticeable catalytic properties and stability under hydrothermal conditions, have been investigated. The influence of the reaction temperature and the effect of the catalytic properties on the distribution of the liquid products have been studied. In the best conditions, 50.3 mol.% and 69.5 mol.% of lactic and levulinic acid have been obtained by using LaCoO3 and LaMnO3, respectively. Apart from the oxidative effect, the affinity hydrogen allowed the catalytic conversion of some key intermediates, such as pyruvic aldehyde and hydroxymethylfurfural, into the desired products. LaMnO3, which has resulted to be the most oxidizable/reducible catalyst at low temperatures, has shown the best catalytic activity among the studied catalysts, promoting the conversion of hydroxymethylfurfural to levulinic acid and giving overall the highest yield
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
New-generation curing units and short irradiation time: The degree of conversion of microhybrid composite resin
No full textThis in vitro study investigated the depth of cure of a microhybrid composite resin when cured with reduced times of exposure to three commercially available curing lights. Different sample thicknesses (1, 2, and 3 mm) were light cured in high intensity polymerization mode (2,400 mW/cm2 for 5, 10, 15, and 20 seconds; 1,100 mW/cm2 for 10, 20, 30, and 40 seconds; and 1,100 mW/cm2 for 10, 20, 30, and 40 seconds, respectively). The degree of conversion (%) at the bottom of each sample was measured by Attenuated Total Reflection Fourier Transform Infrared (ATR F-TIR) analysis after each polymerization step. Data were analyzed by ANOVA for repeated measures, showing the degree of conversion was not influenced by the curing light employed (P = .622) but was significantly influenced by the thickness of composite resin (P < .05). Variations in the degree of conversion vs the shorter irradiation time permitted (T1) were not significant among different lamps but were significant among different thicknesses. The depth of cure of microhybrid composite resin appears not to be influenced by the curing light employed. Increased irradiation time significantly increases the degree of conversion. Thickness strongly influences depth of cure. © 2011 by Quintessence Publishing Co Inc
Concentration quenching in an Er-doped phosphate glass for compact optical lasers and amplifiers
Full text linkIn this paper, highly (up to 5.25 mol% Er2O3) Er-doped phosphate bulk glasses were synthesized by conventional melt-quenching method and their physical, thermal and spectroscopic properties are reported. The influence of Er3+ doping concentration on emission spectra and lifetimes was investigated in order to study the concentration quenching effect on luminescence performance and therefore to evaluate the most suitable rare earth content for developing compact fibre laser and optical amplifier operating at 1.55 μm. A radiative lifetime and a quenching concentration equal to τ0 = 7.05 ms and N0 = 9.92 × 1020 ions/cm3 were respectively calculated by fitting the fluorescence lifetime experimental data with Auzel's limited diffusion model
Reversible insulator-to-metal transition in p(+)-type mesoporous silicon induced by the adsorption of ammonia
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