1,721,034 research outputs found
Direct liquid crystal templating of mesoporous silica and platinum
No full textMesoporous silicas have been prepared with hexagonal (H1) pore morphologies from TMOS/Brij 56/water/HCl mixtures. A detailed study of the synthesis of mesoporous silica from such mixtures revealed that ordered structures are formed at both high (~50 wt%) and low (~0.1 wt%) surfactant concentrations. The liquid crystal phase behaviour of Brij 56 in water showed that at low surfactant concentrations an H1 structure formed from a phase separated solution. At the high concentrations of surfactant the H1 phase was homogeneous throughout the sample and the hexagonal pore structure was a replica of the initial H1 lyotropic phase with ~3.6 nm diameter pores and ~1.7 nm thick walls.Direct liquid crystal templating of platinum has been studied by the reduction of a platinum salt in the aqueous domains of an H1 phase to C16EO8. The most successful method of preparing H1 platinum employed reduction with iron metal at room temperature. BET surface area analysis showed the mesoporous platinum to have a surface area of ~60 m2g-1. This is almost twice the surface area for commercially available platinum black materials. The pore size of the H1 materials was found to be ~2.9 nm with ~3.9 nm thick walls. A phase diagram study of the C16EO8/H2PtCl6/H2O system made it possible to obtain cubic (V1) and lamellar (Lα) mesoporous platinum. Finally, mesoporous silicas have been successfully loaded with H2PtCl6 and reduced to platinum metal as a method of preparing a supported platinum catalyst. The platinum was found to aggregate into particles rather than line the pores of the mesoporous structure after reduction.</p
Ordered mesoporous silicas prepared from both micellar solutions and liquid crystal phases
No full textIn the preparation of mesoporous materials it has been shown that the liquid crystalline properties of the surfactant are an important factor in determining the morphology of the mesostructures, In this study the regularity and morphology of the mesopore structure was examined by X-ray diffraction, transmission electron microscopy and BET surface area analysis as a function of surfactant concentration for the TMOS/Brij 56/HCl (0.5 M) system. The preparation of ordered HI mesoporous silica was shown to take place from both a dilute solution of surfactant (1 Brij 56:1000HCl (0.5 M)) and a concentrated surfactant solution (1Brij 56:1HCl(0.5 M)). Ordered H-1 silica monoliths were prepared with 3.6 nm diameter pores and 1.7 nm thick walls from concentrated Brij 56 mixtures. Similarly ordered H-1 silica micron sized powders were prepared with 3.8 nm diameter pores and 2.1 nm thick walls from dilute Brij 56/mixtures, Comparison of the mesostructure of the silicas with the liquid crystal phase behaviour of the binary Brij 56/water system showed a correlation between the order of the mesoporous material and the phase behaviour of the surfactant at the high concentration of surfactant, At the low concentrations of surfactant the binary Brij 56/water phase diagram does not exhibit liquid crystalline behaviour, However, phase separation of the micellar solution, induced by the presence of silica species, resulted in micron sized domains of liquid crystalline material. These tiny domains acted as moulds for the formation of mesoporous silica
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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