1,721,050 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Synthesis of cationic magnetic nanoparticles and evaluation of their gene delivery efficacy in Hep G2 cells
No full textSelective Depression of Hexagonal Pyrrhotite from Pentlandite Using Starch
Get PDFPentlandite is very important to the mining industry since it is the main source of metallic nickel. However, its separation from hexagonal pyrrhotite is a challenge for processing engineers due to the similar floatabilities of these sulfide minerals. An inefficient separation of these minerals generates serious environmental issues caused by the emissions of sulfur oxide gases during the pyrometallurgy of final concentrates. Although successful, the current depressant used, diethylenetriamine (DETA), is also harmful to the environment when disposed. Due to stringent environmental policies being implemented, the mining industry is under the obligation of researching/developing alternative reagents which are non-toxic and biodegradable. Therefore, new flotation strategies must consider the use of reagents such as polysaccharides. Three non-toxic starch depressants for hexagonal pyrrhotite were used in this study. They include a paste starch with higher molecular weight distribution, a paste starch with lower molecular weight distribution, and a crosslinked starch formed using the paste starch with lower molecular weight distribution and copper ions. We hypothesize that the presence of crosslinking agents such as copper would provide a “driving” effect towards the main gangue mineral. The performance of depressants was investigated in single and binary mineral systems. For single minerals, comparing paste starches, the higher molecular weight paste starch was more detrimental to the recovery of pentlandite and hexagonal pyrrhotite than the lower molecular weight paste starch. In addition, the crosslinked starch further reduced the recoveries of both minerals. A better result for the binary mineral systems considering Ni recovery and Ni grade was achieved by using 9.66x10-6 M of PIBX (equivalent to 240 g/t) and 5 mg/L of starch depressants (equivalent to 660 g/t). Whereas the lower molecular weight paste starch almost did not affect Ni recovery (91.2%) comparing with the collector baseline (92.5%), the higher molecular weight paste starch and the crosslinked starch had a Fe recovery no greater than 31.0%. The choice of the best starch depressant showed to be complex since pentlandite and hexagonal pyrrhotite were able to chemically interact with the starch depressants as verified via XPS. The hydroxyl groups present on the α-D-glucose units of starch bound with the metal hydroxylate species. Moreover, the crosslinked starch also interacts with the mineral surfaces by electrostatic attraction due to the presence of weakly electronegative copper center. Kinetics and equilibrium adsorption tests allowed a more direct comparison of the effect of the starch depressants, regarding the mechanism of depression. It has been proven the importance of a balance of hydrophobic/hydrophilic species on both mineral surfaces. This was further as confirmed by contact angle measurements (Washburn method), QCM-D, and AFM tests. For the paste starches, it has been proposed that the mechanism of depression is related to the hydration levels of the adsorbed depressant layer. The amount of water molecules held by the polysaccharide structure is directly related the packing density (conformation). Furthermore, the latter is a function of the starch molecular weight, showing the importance of this parameter for mineral depression. For the crosslinked starch, however, the distribution of depressants across both mineral surfaces, given in terms of surface coverage, is the most relevant parameter dictating its depressing effect. The findings of this research will contribute with the advancement of topics related to the use of polysaccharides as depressants for sulfide minerals. The utilisation of non-toxic depressants can benefit the industry regarding the mitigation of safety and environmental problems
Variations on the Author
Get PDF“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
Get PDFWe 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
The Mechanism of Floc Formation by Hydrodynamic Cavitation and Its Application on Fine Particle Flotation
Get PDFIn recent decades, hydrodynamic cavitation has been used to enhance fine particle flotation recovery in mineral engineering. Such an increase was mainly attributed to the generation of flocs/aggregates of fine particles during the hydrodynamic cavitation process. However, the mechanism of floc formation in hydrodynamic cavitation still remains unclear. This study aims to fill this knowledge gap regarding the agglomeration mechanism of fine particles in hydrodynamic cavitation.
Fine molybdenite particles with the diameters less than 37 μm were investigated with the cavitation system. The optimized geometry Venturi tube investigated in previous studies of our research group was applied in a hydrodynamic cavitation system for microbubble generation and floc formation. Floc size was measured to study the relationship between the cavitation intensity and flotation efficiency. Under cavitation with inlet air injection, floc size increased to 140 μm efficiently. Microscope images of generated flocs were captured to examine the structure. It was found that cavitated bubbles acted as the bridges between particles in the floc structure. Zeta potential distribution was measured to investigate the interaction between microbubbles and fine particles. Strong attachment of microbubbles and particles were demonstrated in cavitation treatment.
Hydrodynamic cavitation was also applied in micro-flotation of fine particles to study the effect of flocs in the mineral flotation. An increase of 20% in recovery of fine molybdenite was achieved after cavitation with inlet air injection. Fine silica particles in the same size range were used as a comparison. No significant increase of fine silica recovery was found. This observation indicates that cavitation predominantly affects hydrophobic particles based on contact angle results. At last, the flotation of the mixture of molybdenite and silica was investigated to demonstrate the selectivity of hydrodynamic cavitation in mineral processing
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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