1,721,130 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
Calcium Signalling Triggered by NAADP in T Cells Determines Cell Shape and Motility During Immune Synapse Formation
Get PDFNicotinic acid adenine dinucleotide phosphate (NAADP) has been implicated as an initial Ca2+ trigger in T cell Ca2+ signalling, but its role in formation of the immune synapse in CD4+ effector T cells has not been analysed. CD4+ T cells are activated by the interaction with peptide-MHCII complexes on the surface of antigen-presenting cells. Establishing a two-cell system including primary rat CD4+ T cells specific for myelin basic protein and rat astrocytes enabled us to mirror this activation process in vitro and to analyse Ca2+ signalling, cell shape changes and motility in T cells during formation and maintenance of the immune synapse. After immune synapse formation, T cells showed strong, antigen-dependent increases in free cytosolic calcium concentration ([Ca2+] i ). Analysis of cell shape and motility revealed rounding and immobilization of T cells depending on the amplitude of the Ca2+ signal. NAADP-antagonist BZ194 effectively blocked Ca2+ signals in T cells evoked by the interaction with antigen-presenting astrocytes. BZ194 reduced the percentage of T cells showing high Ca2+ signals thereby supporting the proposed trigger function of NAADP for global Ca2+ signalling. Taken together, the NAADP signalling pathway is further confirmed as a promising target for specific pharmacological intervention to modulate T cell activation
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
Synthesis of 7-deaza-8-bromo cyclic adenosine 5′-diphosphate ribose: The first hydrolysis resistant antagonist at the cADPR receptor
No full text7-Deaza-8-bromo cyclic adenosine 5′-diphosphate ribose is synthesised from 7-deazaadenosine via 7-deaza-8-bromo nicotinamide adenine dinucleotide; it is both a more potent antagonist than the 8-bromo derivative and has the advantage of chemical and enzymatic hydrolytic stability.</p
Roles for adenosine ribose hydroxyl groups in cyclic adenosine 5'- diphosphate ribose-mediated Ca<sup>2+</sup> release
No full textCyclic adenosine diphosphate ribose (cADPR) is a naturally occurring and potent Ca2+-mobilizing agent. Structural analogues are currently required as pharmacological tools for the investigation of this topical molecule, but modifications to date have concentrated primarily upon the purine ring. Two novel dehydroxylated analogues of cADPR have now been prepared from chemically synthesized nicotinamide adenine dinucleotide (NAD+) precursors modified in the ribose moiety linked to adenine. ADP-ribosyl cyclase of Aplysia californica catalyzed the conversion of 2'(A)-deoxy-NAD+ and 3'(A)- deoxy-NAD+ into the corresponding 2'(A)-deoxy-cADPR and 3'(A)-deoxy-cADPR analogues, respectively. These analogues were used to assess the effect of 2'- and 3'-hydroxyl group deletion in the adenosine ribose moiety of cADPR on the Ca2+-releasing potential of cADPR. These compounds were found to have comparatively markedly different activities as agonists for Ca2+ mobilization in sea urchin egg homogenate. 2'(A)-Deoxy-cADPR is similar to cADPR, whereas 3'(A)-deoxy-cADPR is at least 100-fold less potent, indicating that the 3'(A)-hydroxyl group, but not the 2'(A)-hydroxyl group, is essential for calcium releasing activity. EC50 values recorded were 32 nM. 58 nM, and 5 μM for cADPR, 2'(A)-deoxy-cADPR, and 3'(A)-deoxy-cADPR, respectively. Moreover, 200 nM 2'(A)-deoxy-cADPR was required to desensitize the cADPR- sensitive Ca2+ channel to a subsequent addition of 100 nM cADPR, but 20 μM 3'(A)-deoxy-cADPR was required to produce the same desensitizing effect. This is in accordance with the 100-fold lower potency exhibited by the latter analogue. To further investigate the importance of the 3'-hydroxyl group, we have also synthesized 3'(A)-O-methyl-cADPR, in which the 3'-hydroxyl group of adenosine has been methylated and its ability potentially to donate a hydrOgen atom in a hydrogen bond has been removed. Although inactive in releasing Ca2+, 3'(A)-O-methyl-cADPR inhibited cADPR-induced Ca2+ release in a dose-dependent manner with an approximate IC50 value of 5 μM, whereas 3'-O-methyladenosine had no effect. This further supports the requirement of a 3'-OH group for Ca2+ releasing activity. In addition, however, it suggests that this group may not be crucial for ligand-receptor recognition. Thus, replacement of the hydrogen atom of the hydroxyl with a methyl group effects a change of activity from an agonist to an antagonist of cADPR- induced Ca2+ release. Two other analogues with modifications in the 2' and/or 3' positions, 3'-cADPR phosphate and 2',3'-cyclic-cADPR phosphate, were synthesized and tested for their Ca2+-mobilizing activity in sea urchin egg homogenates. Both analogues were inactive with respect to both agonistic and antagonistic activities on the cADPR-sensitive Ca2+ release mechanism. These are the first steps toward a wider structure-activity relationship for cADPR, and this is the first study to implicate a crucial role for the adenosine ribose hydroxyl groups of cADPR in the biological activity of this cyclic nucleotide. Additionally, this is the first report of a cADPR receptor antagonist that is not modified at the 8-position of the purine ring.</p
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
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