1,721,342 research outputs found
Syphilis, gonorrhoea and Chlamydial infection among women undergoing legal and illegal abortion in Maputo
No full textSTIs are highly prevalent in legal and illegal bortion groups in Maputo. Urgent interventions are needed to reduce their prevalence and consequently their adverse consequence
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
Catalytic combustion of methane over bimetallic Pd-Pt catalysts: the influence of support materials
No full texthe effect of support material on the catalytic performance for methane combustion has been studied for bimetallic palladium-platinum catalysts and compared with a monometallic palladium catalyst on alumina. The catalytic activities of the various catalysts were measured in a tubular reactor, in which both the activity and stability of methane conversion were monitored. In addition, all catalysts were analysed by temperature-programmed oxidation and in situ XRD operating at high temperatures in order to study the oxidation/reduction properties.
The activity of the monometallic palladium catalyst decreases under steady-state conditions, even at a temperature as low as 470 degrees C. In situ XRD results showed that no decomposition of bulk PdO into metallic palladium occurred at temperatures below 800 degrees C. Hence, the reason for the drop in activity is probably not connected to the bulk PdO decomposition.
All Pd-Pt catalysts, independently of the support, have considerably more stable methane conversion than the monometallic palladium catalyst. However. dissimilanties in activity and ability to reoxidise PdO were observed for the various support materials. Pd-Pt supported on Al2O3 was the most active catalyst in the low-temperature region, Pd-Pt supported on ceria-stabilised ZrO2 was the most active between 620 and 800 degrees C, whereas Pd-Pt supported on LaMnAl11O19 was superior for temperatures above 800 degrees C. The ability to reoxidise metallic Pd into PdO was observed to vary between the supports. The alumina sample showed a very slow reoxidation, whereas ceria-stabilised ZrO2 was clearly faster
Lubrication in aqueous solutions using cationic surfactants ? a study of static and dynamic forces
No full textThis paper concerns lubrication in aqueous surfactant systems where the surfactants adsorb at surfaces, in relative motion, forming either a surfactant monolayer or a multi- (liquid crystalline) layer. The surfactants were of two kinds, viz., a double chain cationic surfactant, didodecyldimethylammonium bromide, DDAB, and a single chain cationic surfactant, dodecyltrimethylammonium bromide, DTAB. Excellent film forming capability was shown for DDAB and interpreted as the result of good packing of the surfactant molecules at the surfaces, i.e., the inherent ability of the surfactant molecules to form liquid crystalline structures at the surface, resulting in good load-carrying capability. This is also reflected in the bulk properties of the surfactants, where DDAB show lamellar liquid crystalline phases at concentrations much lower than DTAB, which does not show good lubrication properties. The results are discussed in terms of film stability of a surfactant layer adsorbed at the surface, which in turn is correlated to the critical packing parameter of the surfactant, in analogy with the Kabalnov?Wennerström theory of emulsion droplet coalescence (Kabalnov, A.; Wennerström, H. Langmuir 1996, 12, 276). The systems were characterized using (i) the surface force apparatus determining the interaction forces between the adsorbed layers at the surfaces and (ii) the EHD rig (elastohydrodynamic rig) determining film formation under shear. The adsorption kinetics and composition at the surface were determined by a quartz crystal microbalance and X-ray photoelectron spectroscop
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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