1,721,019 research outputs found
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
COMPLEX FORMATION OF NICKEL(II) AND COBALT(II) WITH SALICYLIC ACIDS, EQUILIBRIA AND REACTION MECHANISMS
No full textVariations 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
The Effects of Intramolecular Hydrogen-Bonding on the Rates of Complex Formations of Co(II) and Zn(II) with Substituted Salicylic Acids
No full textPotentiometric evaluation of the binding equilibria of the RNA-ethidium bromide system by a new liquid membrane electrode
No full textKinetic and Thermodynamic Studies on Ga3+/PAR Complex Formation in SDS Surfactant Solutions
No full textIn recent years, owing to the awareness on environmental hazards in the wide use of organic solvents for metal ion extraction, selective extraction and concentration of toxic and precious metals from aqueous streams and liquid wastes by new smart technologies has been the object of intense studies. Between these new strategies, micellar media were found to have significant advantages over a two-phase water-organic solvent system for the extraction process.1,2 In addition of lower environmental impact, the micelles are distributed uniformly through the medium as very small (nano-sized) aggregates, therefore avoiding mixing problems due to unhomogeneity. In the presence of a negatively charged surface, such as is provided by the head groups of the surfactant, the metal ion will be electrostatically attracted to the micelle surface and the extractant will concentrate in the hydrophobic core of the micelle. Under these conditions the extent of extraction will be enhanced as the result of a local concentration effect on both reactants.A study on the kinetics and thermodynamics of the reaction between Ga(III) and ligand 4-(2-pyridylazo)resorcinol (PAR) has been done in sodium dodecyl sulphate (SDS) surfactant solutions, by means of the stopped-flow technique and by UV-vis spectroscopy. A rate promotion effect is found for the forward reaction and for the equilibrium constant in the presence of micelles. The maximum catalysis effect is found when the surfactant concentration is just above the cmc (critical micellar concentration), followed by a decrease at higher SDS concentrations. The kinetic constant of complex formation in SDS solutions at pH=4 is much lower that the one measured at pH=6. In fact, under the latter pH conditions, the neutral PAR species prevails. Such a neutral molecule will have lower tendency to condensate on the negative micelle surface than the protonated H3PAR+ species. Further mechanistic details will be discussed
Extraction, separation and recovery of Palladium and Platinum by a kinetic method combined with ultrafiltration
No full textA method is presented allowing separation of palladium from platinum based on the different kineticlability of the two metals. These are let to react with PADA (trans-pyridine-2-azo-p-dimethylaniline) inthe presence of SDS micelles. The kinetic study of the PADA binding to Pd(II) and Pt(II), both in form ofchlorocomplexes, shows that the reactivity of PdCl42−is about 4 × 103-fold higher than that of PtCl42−.The Pd(II)–PADA complex is completely formed in about 30 min and adsorbed on the micelle surface. Inthis lapse of time less than 2% of Pt(II) is complexed. The separation of the two metals is then accom-plished by ultrafiltration. With this procedure 98% of platinum can be recovered in the filtrate. Palladium,present in the retentate, is then recovered using a stripping agent and a multi-step ultrafiltration proce-dure. The most efficient among the stripping reagents tested is HCl 0.05 M (yield 90% after three steps).The extraction yield is independent of the concentration of the SDS micelles ([SDS] = 0.01–0.04 M), thusallowing low concentrations of surfactant to be used with excellent yields.© 2013 Elsevier B.V. All rights reserve
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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