1,721,139 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
Viral protein synthesis in cowpea mosaic virus infected protoplasts
No full textIn contrast to the situation concerning bacterial and, to a lesser extent, animal RNA viruses, little is known about the biochemical processes occurring in plant cells due to plant RNA virus infection. Such processes are difficult to study using intact plants or leaves. Great effort has therefore been spent in developing in vitro cultures of plant protoplasts, but the use of these protoplasts has been seriously hampered by various technical problems.It is clear that plant RNA virus infections give rise to a number of specific reactions in infected cells, particularly at the level of RNA and protein synthesis. The multiplication of these viruses implies a manifold copying of their structural components, namely RNA and protein. These activities clearly require the involvement of other RNA and protein species in view of, for instance, the drastic cytopathic effects that are often caused by infection. Thus, detailed knowledge of virus-induced RNA and protein synthesis is a prerequisite for an understanding of the infection process.In this thesis investigations are described concerning the proteins involved in the multiplication of cowpea mosaic virus (CPMV) in cowpea protoplasts.The relevant properties of CPMV are summarized in chapter 2. Research on CPMV is interesting not only in the field of plant virology as the virus is also of general virological significance. Structurally, for example, CPMV shares a number of striking features with the animal picornaviruses like poliovirus and footand-mouth disease virus. From a molecular biological point of view the multiplication of CPMV presents several intriguing specific questions. CPMV is a multicomponent virus: its genome consists of two different single-stranded RNA molecules occurring in separate nucleoprotein particles, both of which are essential for infection. It would be of interest to learn which functions are specified by the two genome pieces, whether the separate viral components can give rise to some virus-specific biochemical expression within the cell and how they complement each other during normal infection. Characteristic cytopathic structures are induced in plant cells upon infection with CPMV in the form of vesicular membranes embedded in amorphous electron-dense material. It is now well established that replication of the viral RNA is localized in these structures. Information about their development and functioning is thus required.Chapter 2 also contains an introduction to the essential features of plant protoplasts and an enumeration of the diverse possibilities they can offer for the investigation of specific virological problems. Finally, the present state of knowledge about the biochemistry of multiplication of plant viruses, as obtained mainly through the use of protoplasts, is reviewed.The isolation of viable protoplasts from the leaf mesophyll tissue of cowpea requires the stringent control of the growth conditions of the plants (chapter 3). Various factors appeared to influence the quality of the protoplasts and their infectability with CPMV. The combination of cowpea mesophyll protoplasts and CPMV appeared to offer a very attractive system. Based on the original study of HIBI et al. (1975) a procedure was developed for the preparation and infection of the protoplasts, the most rapid and simple one so far described (chapter 3). The major reasons for this are:- a short growth period (about 10 days under the conditions used) is required to obtain suitable leaf material- for an efficient enzymatic digestion of the leaves it is sufficient to damage the lower epidermis by means of carborundum powder and paint-brush instead of stripping off the epidermis with forceps- enzymatic one-step isolation of protoplasts can be achieved by simultaneous digestion with pectinase and cellulase- inoculation of cowpea protoplasts with CPMV does not require the use of polycations, making the preincubations of protoplasts and virus superfluous.Using this standard procedure, synchronous infection in virtually all protoplasts could be routinely established.Radioactive precursors of RNA and protein added to the cowpea protoplast incubation medium were taken up and incorporated into macromolecules to high specific activities (chapter 4). This light-dependent metabolic activity increased during the first 30 h after isolation of the protoplasts. It could be influenced by several metabolic inhibitors. RNA synthesis, for instance, was strongly inhibited by actinomycin D and cordycepin, whereas ot-amanitin and rifampicin had only a slight effect. Protein synthesis in the protoplasts could be blocked completely by means of cycloheximide, and was also sensitive to the action of antibiotics such as chloramphenicol, puromycin and, to a lesser degree, lincomycin. These inhibitor studies, as well as the results of analyses of RNAs and proteins synthesized in the protoplasts, indicated that the metabolic activity of the chloroplasts is low and mainly limited to light-dependent energy generation.The multiplication of CPMV in cowpea mesophyll protoplasts relies upon host-coded DNA-dependent RNA synthesis during the earliest stage of infection. As described in chapter 5, propagation of the virus was completely prevented when protoplast DNA transcription and thereby almost all RNA synthesis was inhibited by means of actinomycin D, provided that the drug was applied at the time of inoculation or immediately thereafter. The degree of inhibition of CPMV replication by actinomycin D rapidly decreased when the antibiotic was added later after inoculation; the production of viral nucleoprotein particles became progressively more resistant to the drug, showing complete resistance at about 8 h after inoculation, a time at which infection was still in its latent phase.Surprisingly, synthesis of CPMV antigen was still demonstrable by immunofluorescent antibody staining techniques in protoplasts in which virus replication had been completely blocked by actinomycin D. Under these circumstances de novo production of viral top component (empty capsids) was observed. In addition to the CPMV capsid proteins, these experiments revealed another 3 viral-related polypeptides in infected protoplasts (molecular weights 170,000, 110,000 and 84,000). Since their synthesis also clearly continued during inhibition of host RNA synthesis by actinomycin D it was concluded that they were coded for by the viral genome.A more detailed analysis of the proteins involved in CPMV multiplication is described in chapter 6. At least 11 proteins not present in mock-infected protoplasts or present in much lower amounts were detected in infected protoplasts. Their molecular weights were estimated to be 170,000, 130,000, 112,000, 110,000, 87,000, 84,000, 68,000,37,000, 30,000,24,000 and 23,000. Host-specific protein synthesis appeared to be hardly affected by C~ infection. Virusspecific proteins therefore had to be distinguished from a large variety of protoplast proteins. This appeared to be greatly facilitated by radioactive labeling of the protoplasts for short periods during a suitable phase of the infection cycle and by subcellular fractionation of the protoplasts. The treatment of the particulate fractions with the mild detergent digitonin yielded extracts in which proteins could be detected by polyacrylamide gel electrophoretic analysis that otherwise remained hidden by a general high background of radioactivity upon direct analysis of the untreated particulate fractions.All of the proteins apparently concerned in CPMV infection were most clearly observed late in infection. None of them was detectable during the actinomycin D-sensitive latent period. The 170 and 30 kilodalton proteins were the first detectable, namely from about 10 h after inoculation. All others became apparent about 6 h later.The induction of the characteristic cytopathic structures in CPMV-infected cells suggests the induction and/or stimulation of synthesis of a large number of proteins by the virus. Upon fractionation these proteins should appear in the particulate fractions of the protoplasts. However, only 2 virus-induced polypeptides (112 and 68 kilodalton) were demonstrated exclusively in these fractions. Other components of the cytopathic structures presumably remained in the extracted pellet residues.In chapter 8 further characterization of the viral-related proteins found in CPMV-infected protoplasts is described. The 37, 24 and 23 kilodalton proteins were identified as viral capsid proteins by comparing their electrophoretic mobility in polyacrylamide gels with those of proteins from purified CPMV and by immunoprecipitation with anti-CPMV serum. They occurred in the soluble fraction of protoplasts only in viral particles, not as free proteins. The 170 and 30 kilodalton polypeptides also appeared to be virus-specific and to be coded for by CPMV bottom component RNA: they comigrated in polyacrylamide slabgels with the main products of in vitro translation of this RNA in a messengerdependent lysate of rabbit reticulocytes. These polypeptides were also induced in protoplasts after inoculation with purified CPMV bottom component. Under these conditions some other viral-related proteins were also synthesized, but not the viral capsid proteins. In contrast, inoculation with purified CPMV middle component did not delectably affect protoplast protein synthesis. These experiments strongly suggest that CPMV B-RNA specifies one or more early functions one of which being the replicase function, while M-RNA specifies late functions, particularly the viral capsid proteins.Since the total size of the viral-related proteins by far exceeded the theoretical coding potential of the CPMV genome, the occurrence of precursor-product relations was investigated by means of pulse-chase experiments and by attempting to accumulate possible precursors by blocking their proteolytic processing. The results of the latter method were negative. Upon chasing the 35 S-methionine label with unlabeled amino acid the 87,000 dalton polypeptide appeared to be unstable, as was a protein with the same electrophoretic mobility synthesized in uninfected protoplasts. This protein thus probably represents a host-specific protein the synthesis of which is stimulated by CPMV infection. Furthermore, these experiments revealed that several discrete oligopeptides were cleaved from the smaller CPMV coat protein after assembly into a virion. Although the involvement of precursor- product relations could not be definitely excluded on the basis of the methods used, another possible mechanism of viral gene expression was also investigated, namely the occurrence of subgenomic viral messengers. Upon analysis of 32 P-labeled RNA from CPMV-infected protoplasts by polyacrylamide gel electrophoresis, 2 RNAs of genome length were the only detectable virus-specific polynucleotides. These results suggest a mechanism for the translation of the CPMV genome using internal initiation sites. Further research is, however, required to unequivocally elucidate the strategy of the viral gene expression.<p/
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