1,721,055 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
Notch signaling balances adult neural stem cell quiescence and heterogeneity
Full text linkAdult neurogenesis continues throughout life in the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampal dentate gyrus (DG) of mammals. At the base of adult neurogenesis lie adult neural stem cells (NSCs). These cells can either be found in a dormant, non-dividing state (quiescent) or in a proliferating state (active). Over the last three decades the field of neurogenesis has expanded, but there are still open questions with regards to adult NSC maintenance and potential capacity. Over the course of my PhD studies I addressed three major questions of adult NSC maintenance.
(1) What are the differences between active and quiescent NSCs?
(2) Do NSCs have similar maintenance factors in the SVZ and the SGZ?
(3) What are the capacities of distinct subtypes of NSCs and progenitors to respond to external stimuli?
I was able to show that in the adult mouse brain, Notch2 is the gatekeeper of quiescent NSCs in both neurogenic niches, the SVZ and the SGZ. The loss of this Notch paralogue led to the activation of quiescent NSCS and a prolonged and abnormal activation, followed by NSCs exhaustion in the long term. If Notch1 was deleted in addition to Notch2, quiescent and active NSCs are no longer maintained properly and will differentiate to a neural fate. Thus an intricate interplay between Notch1 and Notch2 is needed for adult NSC maintenance in both neurogenic niches.
In the SVZ the receptors Notch1 and Notch2 are coexpressed on NSCs. We addressed NSC identity also in the second neurogenic niche, the SGZ, where the receptors are also coexpressed by NSCs. The loss of Notch2 led to the activation of quiescent NSCs and an increased production of neuroblasts.
The differential signal requirement for the maintenance of quiescent and active NSCs raises the question, whether these distinct cell populations might have unique functions in response to external physiological and/or pathological stimuli. In order to address this question we characterized the SGZ in great detail at different ages. In the geriatric SGZ active NSCs were lost and the NSCs that remained were quiescent. These quiescent NSCs have the capacity to replenish the active NSC pool upon induction of epileptic seizures. On the other hand, administration of antidepressants left the NSCs unaffected initially. It was the amplifying progenitor pool that responded. In long-chase experiments the NSCs were then reactivated by either the resulting induced changes from the amplifying progenitors or a delay in NSC response.
NSC maintenance in the adult murine brain is an intricate mechanism highly dependent on the proper internal and external mechanisms. In the work presented here, I will illustrate the importance of Notch signaling in NSC maintenance and the high level of heterogeneity within the NSC pool and the NSC niche
Visualising Asymmetry: Monitoring the segregation of proteins important in neurogenesis
No full textAsymmetric cell division is an essential mechanism in the process of neurogenesis, which produces cells with different fates. Currently, our knowledge of which cellular components are subject to asymmetric segregation is lacking. Fatty acid synthase (FASN) has an important function in dividing stem cells but not in non-dividing cells, which makes it a good candidate to be unevenly segregated to the stem cell. Thus, I used the iCOUNT system to investigate the segregation pattern of FASN in dividing cells. The iCOUNT is a novel genetic tool that relies on an inducible colour switch that facilitates the investigation of asymmetrical segregation of intracellular components. I was able to tag FASN with the iCOUNT construct using CRISPR/Cas9, allowing me to determine that FASN is localised to the cytoplasm and segregated mostly symmetrically in mouse embryonic stem cells and neural stem cells that were tested. However, some asymmetry was observed with time, likely due to an accumulation of damage. To determine whether this asymmetry correlates with intrinsic cellular asymmetry I aimed to tag centrosomal components with the iCOUNT construct allowing the distinction between young and old centrosomes. Visualising centrosomes by tagging Centrin1 was unsuccessful. However, by targeting Pericentrin (PCNT), an integral component of the pericentriolar material, the centrosomes and their distinct stages were clearly visible. Further investigation is necessary to characterise PCNT inheritance, before it can be used to answer some of the fundamental questions of asymmetry. Finally, I developed an improved iCOUNT system utilizing a double colour switch based on two serial recombination events enabling the visualization of the tagged protein for more cell divisions (called miCOUNT). These data show the potential of the iCOUNT/miCOUNT system as a tool to visualise asymmetric segregation of various proteins in real time
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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