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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
Redox State Of Erythrocyte Peroxiredoxin 2 During Oxidative Stress And Its Effect On Membrane Binding
Get PDFPeroxiredoxin 2 (Prx2) is the third most abundant protein in erythrocytes. It is a thiol-specific antioxidant protein that is able to reduce hydroperoxides. Prx2 is a physiologically vital protein, since mice lacking Prx2 develop severe haemolytic anaemia. Much is known about Prx2 structure and activity, and its redox state has been linked to several functions in other cells. However, if and how the redox state of erythrocyte Prx2 is modified during inflammation or blood storage has not been established. Further, Prx2 membrane binding in erythrocytes has been observed frequently, but it is not clear if Prx2 redox state affects membrane binding. The aims of this thesis were to investigate how inflammation, neutrophil activation and blood storage affect Prx2 redox state, and how Prx2 membrane binding is influenced by its redox state.
When oxidised, Prx2 is converted to a disulfide-linked homodimer. Non-reducing SDS-PAGE and Western blotting was exploited to measure the redox state of Prx2. Prx2 was oxidised when exposed to hydrogen peroxide (H2O2). Neutrophils generate H2O2 during inflammation, so activated neutrophils were able to oxidise Prx2 in neighbouring erythrocytes. Prx2 oxidation by neutrophil-derived H2O2 was also observed in a mouse model of endotoxaemia, raising the possibility of Prx2 being a useful real-time marker for oxidative stress in inflammatory diseases.
For blood transfusions, erythrocytes are stored at 4 °C for up to six weeks. Under standard storage conditions, Prx2 remained mainly reduced during the first three weeks, after which oxidised Prx2 accumulated progressively. While supplementation with dihydrolipoic acid (DHLA) showed some promise in prevention of Prx2 oxidation, storage of erythrocytes in an alternative buffer similar to a recently FDA approved solution with high pH and some buffering capacity delayed the onset on Prx2 oxidation successfully. When the antioxidant capacity of stored erythrocytes was tested with additional H2O2, it was revealed that while Prx2 recycling was impaired, it was not absent. This is likely due to a heterogeneous population of erythrocytes, where older cells may lose their ability to recycle oxidised Prx2. Prx2 could therefore be a useful biomarker for oxidation in stored erythrocytes.
Prx2 binds to the erythrocyte membrane, which was previously suggested to depend on Prx2 redox state. In whole erythrocytes, Prx2 membrane binding increased with calcium, and decreased with H2O2, while the redox state of Prx2 was only affected by the latter. Furthermore, when both calcium and H2O2 were added, no Prx2 was lost from the membrane, indicating that two different mechanisms are involved in Prx2 membrane binding. After purification of erythrocyte Prx2, isolation of erythrocyte membranes, and incubation of the membranes with hyperoxidised, reduced and oxidised Prx2, it was established that membrane binding was independent of Prx2 redox state. This indicates that H2O2 acts on another component of erythrocytes to inhibit binding. When oxyhaemoglobin and haemichromes, which are denatured haemoglobin, were added, the haemichromes interfered with Prx2 binding to the membrane. Haemoglobin had no effect. This is consistent with the hypothesis that Prx2 protects the membrane from oxidative damage arising from haemoglobin oxidation, but is displaced during erythrocyte senescence
Redox State Of Erythrocyte Peroxiredoxin 2 During Oxidative Stress And Its Effect On Membrane Binding
No full textPeroxiredoxin 2 (Prx2) is the third most abundant protein in erythrocytes. It is a thiol-specific antioxidant protein that is able to reduce hydroperoxides. Prx2 is a physiologically vital protein, since mice lacking Prx2 develop severe haemolytic anaemia. Much is known about Prx2 structure and activity, and its redox state has been linked to several functions in other cells. However, if and how the redox state of erythrocyte Prx2 is modified during inflammation or blood storage has not been established. Further, Prx2 membrane binding in erythrocytes has been observed frequently, but it is not clear if Prx2 redox state affects membrane binding. The aims of this thesis were to investigate how inflammation, neutrophil activation and blood storage affect Prx2 redox state, and how Prx2 membrane binding is influenced by its redox state.
When oxidised, Prx2 is converted to a disulfide-linked homodimer. Non-reducing SDS-PAGE and Western blotting was exploited to measure the redox state of Prx2. Prx2 was oxidised when exposed to hydrogen peroxide (H2O2). Neutrophils generate H2O2 during inflammation, so activated neutrophils were able to oxidise Prx2 in neighbouring erythrocytes. Prx2 oxidation by neutrophil-derived H2O2 was also observed in a mouse model of endotoxaemia, raising the possibility of Prx2 being a useful real-time marker for oxidative stress in inflammatory diseases.
For blood transfusions, erythrocytes are stored at 4 °C for up to six weeks. Under standard storage conditions, Prx2 remained mainly reduced during the first three weeks, after which oxidised Prx2 accumulated progressively. While supplementation with dihydrolipoic acid (DHLA) showed some promise in prevention of Prx2 oxidation, storage of erythrocytes in an alternative buffer similar to a recently FDA approved solution with high pH and some buffering capacity delayed the onset on Prx2 oxidation successfully. When the antioxidant capacity of stored erythrocytes was tested with additional H2O2, it was revealed that while Prx2 recycling was impaired, it was not absent. This is likely due to a heterogeneous population of erythrocytes, where older cells may lose their ability to recycle oxidised Prx2. Prx2 could therefore be a useful biomarker for oxidation in stored erythrocytes.
Prx2 binds to the erythrocyte membrane, which was previously suggested to depend on Prx2 redox state. In whole erythrocytes, Prx2 membrane binding increased with calcium, and decreased with H2O2, while the redox state of Prx2 was only affected by the latter. Furthermore, when both calcium and H2O2 were added, no Prx2 was lost from the membrane, indicating that two different mechanisms are involved in Prx2 membrane binding. After purification of erythrocyte Prx2, isolation of erythrocyte membranes, and incubation of the membranes with hyperoxidised, reduced and oxidised Prx2, it was established that membrane binding was independent of Prx2 redox state. This indicates that H2O2 acts on another component of erythrocytes to inhibit binding. When oxyhaemoglobin and haemichromes, which are denatured haemoglobin, were added, the haemichromes interfered with Prx2 binding to the membrane. Haemoglobin had no effect. This is consistent with the hypothesis that Prx2 protects the membrane from oxidative damage arising from haemoglobin oxidation, but is displaced during erythrocyte senescence
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
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