1,721,161 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
Inhibition of secretion by asexual reproduction in Aspergillus niger
No full textThe aim of this Thesis was to study mechanism involved in zonal secretion in colonies of A. niger with emphasis on sporulation inhibited secretion. These mechanisms may be targets to improve A. nigeras a cell factory. I focused in particular on A. niger homologues of fluG and veA that are known sporulation genes in A. nidulans. Moreover, I studied the role of light because asexual reproduction is known to occur mainly in the light in A. nidulans. This suggests that sporulation and, as a consequence of this, secretion are influenced by light in A. niger
Sporulation inhibited secretion in Aspergillus niger
No full textAspergillus niger is abundantly found in nature. It degrades dead material of plants and animals but can also be a pathogen of these organisms. Aspergillus niger is also important for mankind because it is one of the main organisms used for the industrial production of enzymes. These enzymes are released into the culture medium, from which they can be easily isolated. I have shown for the first time in a quantitative way that different zones of colonies of Aspergillus niger release different enzymes. This finding is instrumental in understanding how fungi degrade organic substrates in nature. Notably, I identified a zone in colonies that does not secrete proteins. This zone has the capacity to reproduce asexually. This suggested that sporulation inhibits secretion of proteins. Indeed, inactivation of the sporulation genes flbA, and fluG results in protein secretion throughout the mycelium. Inactivation of flbA also resulted in more protein release in the medium, which is partly explained by the thinner cell walls of this mutant. Thinner cell walls were also obtained by adding the antibiotic cycloheximide to the culture medium. This also resulted in increased protein release. Secreted proteins are easily trapped in a thicker cell wall, or might associate with cell wall components compared to hyphae with thinner cell walls. Therefore, a colony that forms hyphae with thin cell walls will release high amounts of protein in the culture medium. This finding and the fact that sporulation inhibits protein release is of interest for the industry to improve A. niger as a cell factor
Fungal heterogeneity; from zones to compartments
No full textHeterogeneity in fungi is ubiquitous with respect to many variables. In this thesis it is shown that 3D micro-colonies are heterogeneous with respect to protein expression. Showing a peripheral shell where the glucoamylase gene, the feruloyl esterase gene and the α-glucuronidase gene are expressed. This expression zone is relatively stable, enabling human intervention to control micro-colony size and thereby increasing protein production efficiency. Moving from zones to hyphae it is shown that environmental factors impact occlusion of septa, enabling heterogeneity to arise between hyphae and hyphal compartments. It is shown that fungal hyphae can be divided into secretor and persistor categories, demonstrating the positive impact of heterogeneity on fungal fitness. Hyphal apical compartments in turn are shown to be heterogeneous in their capacity to maintain their growth rate after they have been severed from their originating mycelium. The ability to occlude the apical septum is not a predictor of survival of apical compartments after dissection. In contrast, the relative cytoplasmic volume remaining in an apical compartment could predict the maintaining of growth rate. The parental hypha of a severed compartment was shown to be able to continue growth after the apical zone of a hypha was lost. However, parental hyphae that were reduced in their capability to plug septal pores showed reduced ability to reinitiate growth. The ability of fungal apical compartments to maintain their growth rate after separation from their originating mycelium seems to be commonplace. Single second compartment are severely reduced in their capacity to reinitate growth at the same rate as apical compartments, nevertheless functioning as a back-up in case of catastrophic loss of mycelium
Intercompartmental streaming in Aspergillus
No full textFilamentous fungi colonize dead or living substrates by means of a network of hyphae called a mycelium. They secrete enzymes to extracellularly degrade organic polymers. The degradation products are taken up by the fungus to serve as nutrients. Hyphae grow at their apices and branch sub-apically. They are compartmentalized by septa that contain a central pore. This pore allows for inter-compartmental streaming of nutrients and even organelles. Therefore, the cytoplasm within the mycelium is generally regarded as continuous. I showed that cytoplasmic streaming of the reporter protein GFP occurred in both directions at a rate of 15 µm s-1. The rate decreased when the reporter was fused to the cytosolic protein GPD. Probably, GPD is part of a protein complex that includes membrane proteins. Membrane docking and release could explain the decreased velocity. Woronin bodies plug septa when hyphae are mechanically injured. This prevents cytoplasmic bleeding. Woronin bodies are specialized peroxisomes that contain a core of the Hex1 protein. In my Thesis I show that about 35% of the septa are already plugged in intact growing hyphae of Aspergillus. Plugging was shown to be a reversible process. A strain in which the hex1 gene was deleted could no longer plug septa. Interestingly, when Aspergillus niger was subjected to low or high temperature or to hypertonic conditions 75-90% of the septa were plugged. Septal plugging after cold shock was shown to be reversible. Previously, it was shown that the glucoamylase (glaA) gene is heterogeneously expressed in the A. niger mycelium. In this Thesis it is shown that glaA is no longer heterogeneously expressed in a hex1 deletion strain. The loss of heterogeneity can be explained by uninterrupted cytoplasmic streaming of RNA and or protein. Taken together, it is shown for the first time that the cytoplasm of a vegetative mycelium of Aspergillus is not a continuous system
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
- …
