1,720,968 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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Supramolecular Gels : Organogels, Aerogels And Tunable, Multi-color, Luminescent Hydrogels
Get PDFChapter 1: Supramolecular gels and their applications
Gels are viscoelastic materials composed of a solid-like three dimensional fibrillar network that is embedded in a liquid. Supramolecular gels belong to a class of gels which are derived from low molecular weight compounds (typically < 1000). A variety of non-covalent interactions like H-bonding, π-π stacking, donor-acceptor, metal coordination, solvophobic and van der Waals interactions are involved in the formation of the self-assembled fibrous networks (SAFIN’s) in these gels. These non-covalent interactions are weak in nature and as a result, these gels can be reverted back to sol by heating and this process is reversible. These gels are further classified as hydrogels, organogels and aero/xerogels depending on the medium they encompass. Although low molecular weight gelators were known in the early part of the 20th century, it is only in the last two decades that this field has generated widespread interest among scientists. In the 90s, the investigations on these kinds of gels mainly focused on designing new gelator molecules. However, during the last decade, the research interest in this field has shifted more towards designing functional gels. Such gels
Scheme 1. Various applications of functional supramolecular gels
have been extensively utilized in the templated synthesis of inorganic nanomaterials, in making hybrid materials, as synthetic light harvesting systems, as sensors, in the field of biomaterials such as drug delivery, screening of enzyme inhibitors and tissue engineering and also in the field of organic optoelectronics. In this chapter a few selected examples from each of these fields are highlighted.
Chapter 2: Charge transfer induced organogels from 2,3dialkoxyanthracenes and 2,4,7-trinitrofluorenone
2,3-Di-n-alkoxyanthracenes formed charge transfer (CT) interaction promoted organogels in the presence of electron acceptor 2,4,7-trinitrofluorenone (TNF). These dialkoxyanthracences (in the absence of TNF) have been reported previously to form gels in a variety of organic solvents. The gelation property was found to be dependent on the chain length and the derivatives with C6-C16 chains were found to be gelators. On the other hand derivatives with C5-C1 chains were found to be non-gelators. It was found that TNF not only modulated the gelation property of the efficient organogelators, it also transformed the weak and non-gelators into efficient gelators. This charge transfer induced gelation was observed for the derivatives with C10-C4 chains in alcoholic and hydrocarbon solvents whereas the shorter chain derivatives C3-C1 did not form gels. Several other alkoxy and dialkoxy derivatives with substituents in other positions did not show gelation in the presence of TNF. These results suggested that two structural aspects are necessary for these derivatives to form CT gels- the alkoxy chain length and the position of the alkoxy substituents. The thermal stability of all these gels was found to be maximum with a 1:1 stoichiometry of the donor and the acceptor. The common observation, the intensification of color in going from the sol to the gel phase, supported the crucial role of the charge transfer interaction behind the formation of these gels. The rheological characterization of the gels demonstrated that they
Figure 1. Chemical structures of 2,3-dialkoxyanthracenes and TNF (middle) and a fluorescence confocal microscopy image (left) and a photograph (right) of DDOA-TNF gel. behaved like viscoelastic soft solids.
Chapter 3: A new class of perfluorinated derivatives of bile acids: Synthesis and gelation properties
A new class of bile acid based gelators was designed by connecting the side chains of the facially amphiphilic bile acid with perfluoroalkyl chains of different lengths through two different ester linkages-–O-(CO)-and –(CO)-OCH2-. All these three structural aspects i.e. the bile acid moiety, the fluoroalkyl chain length and the spacer were found to influence the gelation properties of the derivatives. Depending on them, there was a variation in terms of the nature of the solvent gelated, the CGCs, the mechanical properties of the gels, etc among the derivatives. The deoxycholic and lithocholic derivatives with the spacer –O-(CO)-formed gels in aromatic hydrocarbons and also in DMSO depending on the fluoroalkyl chain length. The mechanical properties of the gels formed in DMSO were found to be dependent on the bile acid moiety and the fluoroalkyl chain length. In general, the deoxy analogues showed higher elasticity, stiffness and yield stress values for their gels than the litho derivatives. The perfluorinated derivatives having the spacer –(CO)-OCH2-showed gelation properties in organic-aqueous media and in DMSO. Interestingly, organogelation was observed in the deoxy and lithocholic derivatives from both spacer series whereas in the literature most of the bile acid based organogelators are derived from cholic acid.
(b) (c) Figure 2. (a) Perfluorinated derivatives of bile acids, (b) photographs of a few DMSO gels and (c) TEM image of a xerogel of a deoxy derivative
Chapter 4: Composite aerogels and organogels from 2,3didecyloxyanthracene and bile-perfluoro derivatives
Aerogels are unique materials among solids. They have extremely low densities (up to 95% of their volume is air), large pores and high inner surface area. As a result aerogels have very interesting physical properties such as extremely low thermal conductivity, low sound velocity and high optical transparency. There are only a few reports of aerogel formation by low molecular weight gelators. We have investigated the aerogel formation ability of three long 7 chain perfluoroalkyl esters (two deoxycholic and one lithocholic derivative, chart 1) in supercritical CO2. A deoxy derivative, formed aerogel in sc-CO2. When mixed with DDOA (which has been reported previously to form good aerogels in sc-CO2), the perfluoro compound formed aerogels of better quality. The mixed aerogels were characterized by the presence of very large fibers in the micron range (as observed in the aerogel formed by only the fluoro derivative) as well as fibers of smaller size observed in pure DDOA aerogel. We also investigated the behavior of the composite systems in organic solvents. It was found that in DMSO, another deoxy derivative,
Figure 3. SEM images of a mixed aerogel of DDOA-DC23C13F27 (left) and a mixed organogel (DMSO) of DDOA-DC23C11F23 (right).
DC23C11F23 formed gels with higher thermal stability and improved mechanical properties compared to the native gels of the perfluoro compound or DDOA.
Chapter 5: Hydrogels from lanthanide(III) cholates: Tunable, multiple color luminescence from hydrogels and xerogels
In this chapter, facile hydrogel formation by several lanthanide cholates is reported. When sodium cholate was added to aqueous solutions of Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Yb(III) and sonicated, the mixtures formed gels within a few seconds. The gels thus obtained were transparent/translucent and thermoirreversible. Rheological measurements showed that all of them could be classified as viscoelastic soft solids. A naphthalene derivative, 2,3-dihyroxynaphthalene was found to sensitize Tb(III) emission very efficiently in its cholate gel when doped in micromolar concentrations. The importance of the gel matrix behind sensitization of Tb(III) was demonstrated by the inefficiency of the same sensitizer DHN in an SDS micellar solution. In mixed gels of Tb(III)-Eu(III) doped with DHN, a energy transfer pathway was found to occur from the sensitized Tb(III) to Eu(III). By a simple tuning of the ratio of these two lanthanide ions, multiple color emissive gels could be made.The emissive properties of the hydrogels were retained in the xerogels and the suspensions of these xerogels in n-hexane were used for making luminescent coatings on glass surface.
Figure 4. Tunable, multi-color luminescent hydrogels and xerogels of lanthanide cholate
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