1,721,161 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
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
Root effect also functions modulating the hemichrome stability in tetrameric hemoglobins
No full textOxidation of hemoglobins leads to the formation of Fe(III) forms, whose relevance spans from biochemical to physiological aspects 1. Here we report a combined EPR/X-ray crystallography study at acidic pH on six ferric tetrameric hemoglobins (Hbs), five isolated from the Antarctic fish species Trematomus bernacchii, Trematomus newnesi, and Gymnodraco acuticeps, and one from the sub-Antarctic fish Cottoperca gobio. Our data reveal that, in all the studied Hbs, aquomet form and two hemichromes coexist at acidic pH, analogously to what happens at physiological pH 2. Nevertheless, the EPR analysis reveals that, only for the three Root effect hemoglobins 3,4, a significant amount of pentacoordinated (5C) high-spin Fe(III) species appears at acidic pH. The crystal structure at acidic pH of the ferric hemoglobin from Trematomus bernacchii, endowed with Root effect 4, is also reported at 1.7 Å. Indeed, this structure reveals a 5C state both at α- and β-chains within a T-like quaternary structure. The ability of the Antarctic fish Hbs to form 5C states in various conditions prompted us to perform a peroxidase activity study. These proteins exhibit a peroxidase activity higher than that observed for mammalian and temperate fish Hbs , thus suggesting that a partial hemichrome state in tetrameric Hbs does not protect them from peroxidation as previously proposed 5. This work was financially supported by PNRA (Italian National Programme for Antarctic Research) 1 A. Vergara, L. Vitagliano, G. di Prisco, C. Verde, and L. Mazzarella, Meth. Enz. 436A, 421 (2008). 2 A. Vergara, M. Franzese, A. Merlino, L. Vitagliano, G. di Prisco, C. Verde, H. C. Lee, J. Peisach, and L. Mazzarella, Biophys. J. 93, 2822 (2007). 3 L. Mazzarella, G. Bonomi, M. C. Lubrano, A. Merlino, A. Vergara, L. Vitagliano, C. Verde, and G. di Prisco, Proteins: Struct. Funct. Bioinf. 62, 316 (2006). 4 L. Mazzarella, A. Vergara, L. Vitagliano, A. Merlino, G. Bonomi, S. Scala, C. Verde, and G. di Prisco, Proteins: Struct. Funct. Bioinf. 65, 490 (2006). 5 L. Feng, S. Zhou, L. Gu, D. Gell, J. Mackay, M. Weiss, A. Gow, and Y. Shi, Nature 435, 697 (2005)
Bis-Histidyl adducts in tetrameric hemoglobins
No full textIn the last decade crystallographic evidence for endogenous coordination at the sixth coordination site of the heme iron has been reported for monomeric haemoglobins (Hbs) in both the ferrous (haemochrome) and ferric (haemichrome) oxidation state. Usually, the sixth ligand is provided by the imidazole side chain of a His, the only putative ligand normally present in the distal site of the heme pocket. More recently, structural and spectroscopic evidence has been reported, which show that the bis-histidyl adduct in the ferric state represents a common accessible ordered state also for several tetrameric Hbs isolated from Antarctic fish, both in the solid and solution state. Bis-histidyl coordination was also discovered in the crystals of horse met-Hb exposed to acidic pH. All these crystal structures are characterised by a different binding state of α and β chains. Tetrameric Hbs with all chains in the bis-histidyl coordination state have not yet been found. Herein we review the structural details of the recent results in this field, together with solution studies on the pathway of haemichrome formatio
Structure and function of hemoproteins from cold-adapted organism
No full textEnvironmental oxygen availability certainly plays a key role in the evolution of polar marine life, as suggested by the physiological and biochemical strategies that the organisms have adopted to acquire, deliver and scavenge oxygen.
The psychrophilic Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 gives the opportunity to explore the cellular strategies adopted in vivo by cold-adapted microorganisms to cope with cold and high oxygen concentration. Within vertebrates, the dominant suborder Notothenioidei of the Southern Ocean is one of the most interesting models to study the evolutionary biological responses to extreme environment.
Hemoproteins of cold-adapted organisms are likely to fulfil important physiological roles, not only in delivering oxygen to cells, but also in protecting them from the nitrosative and oxidative stress.
This thesis will in particular focus on: (i) the structural and functional features of globins of the Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125, (ii) the role of neuroglobin (Ngb) recently identified in the brain of Antarctic notothenioid fish.
The genome of the cold-adapted bacterium P. haloplanktis TAC125 contains multiple genes encoding three distinct monomeric hemoglobins (Hbs) exhibiting a 2/2 -helical fold (2/2Hb). One of these 2/2Hb (Ph-2/2HbO) has been over-expressed and characterised by spectroscopic analysis, kinetic measurements and computer simulation approaches (Howes et al., 2011; Giordano et al., 2011). The results indicate unique adaptive structural properties, that overall confer higher flexibility to the protein and may facilitate its functioning in the cold by providing greater freedom for the correct positioning of ligand(s). Similar to Ngb, the recombinant protein is hexacoordinated in the ferric and ferrous forms, and shows a strong dependence on pH (Howes et al., 2011; Giordano et al., 2011).
Polar fish are a suitable model to learn more about the function of globins in the brain, and especially about their role in species devoid of Hb and Myoglobin (Mb).
The finding that Antarctic icefishes retain the Ngb gene despite having lost Hb, and Mb in most species, suggests a crucial function. The function of Ngb needs to be ascertained, because it may have important implications in the physiology and pathology of the brain.
The first structural model of fish Ngb was described using molecular dynamics simulations. Specifically, Ngb genes from a colourless-blooded Antarctic icefish species (Chaenocephalus aceratus), and a related red-blooded species (Dissostichus mawsoni), were cloned, the recombinant proteins were expressed and purified, and then sequenced and analysed. Both Antarctic fish Ngbs are hexacoordinated, but have some peculiarities that differentiate them from mammalian counterparts: they have extensions in the N and C termini, interacting with the EF loop, and a gap in the alignment that changes the CD-region structure/dynamics, that has been found to play a key role in human Ngb.
The adaptive modifications to compensate for the effects of low temperature appear to primarily rely on a higher flexibility of key parts of the molecular structure and/or decreased overall stability. At all levels analysed, the functionally most crucial adaptation to permanently low temperatures apparently requires molecular flexibility to support cell functioning. Proteins are the major targets for the ensuing mechanisms of adaptation
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
- …
