1,720,981 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
Discovery of novel inhibitors of bacterial biofilm formation targeting enzymes involved in the metabolism of the second messenger cyclic-di-GMP
No full textINTRODUCTION: Bacteria are able to switch between a single cell (planktonic) lifestyle and a biofilm (community) lifestyle. In pathogenic bacteria, growth as biofilm protects bacterial cells against the host immune system and increases tolerance to antibiotic treatment, thus resulting in chronic infections. The bacterial second messenger cyclic-di-GMP (c-di-GMP) plays a pivotal role in biofilm formation, by promoting production of adhesion factors such as extracellular polysaccharides (EPS). Two classes of enzymes are involved in c-di-GMP metabolism: diguanylate cyclases (DGCs), which synthesize c-di-GMP, and phosphodiesterases (PDEs) that hydrolyze the signal molecule. Usually, a high intracellular c-di-GMP concentration correlates with EPS production and biofilm formation. However, exposure of Pseudomonas aeruginosa to subinhibitory concentration of the aminoglycoside antibiotic tobramycin stimulates biofilm formation through the PDE activity of the Arr protein. This result suggests that biofilm formation can also respond to low intracellular c-di-GMP levels. The enzymes involved in c-di-GMP metabolism are widely conserved in Bacteria, but they are not present in upper eukaryotes. Thus, the proteins involved in c-di-GMP metabolism are a very interesting target for antimicrobial compounds with anti-biofilm activity.
METHODS: To screen for specific inhibitors of enzymes involved in c-di-GMP metabolism, we have developed a set of microbiological assays that rely on detection of c-di-GMP-dependent EPS production using specific dyes such as Congo Red. Intracellular c-di-GMP levels can then be measured directly by HPLC determination.
RESULTS: We have tested over 1,000 chemical compounds in our screening system. Interestingly, we found that sulfathiazole, but not other chemically-related sulfonamide antibiotics, can inhibit both DGC and PDE activity, possibly suggesting that sulfathiazole can bind to the c-di-GMP binding domain of these proteins.
DISCUSSION: Sulfathiazole represents the first example of a drug able to affect biofilm formation by interfering with c-di-GMP metabolism. The precise mechanism of biofilm inhibition by sulfathiazole is currently under investigation
Monitoring of diguanylate cyclase activity and of cyclic-di-GMP biosynthesis by whole-cell assays suitable for high-throughput screening of biofilm inhibitors
No full textIn Gram negative bacteria, production of bis-(3’,5’)-cyclic diguanylic acid (c-di-GMP) by diguanylate cyclases (DGCs) is the main trigger for production of extracellular polysaccharides (EPS) and for biofilm formation. Mutants affected in c-di-GMP biosynthesis are impaired in biofilm formation, thus making DGCs interesting targets for new antimicrobial agents with anti-biofilm activity. In this report, we describe a strategy for the screening for DGC inhibitors consisting of a combination of three microbiological assays. The primary assay utilizes an Escherichia coli strain overexpressing the adrA gene, encoding the DGC protein AdrA, and relies on detection of AdrA-dependent cellulose production as red colony phenotype on solid medium supplemented with the dye Congo red (CR). Presence of DGC inhibitors blocking AdrA activity would result in a white phenotype on CR medium.The CR assay can be performed in 96-well microtiter plates, making it suitable for high-throughput screenings. To confirm specific inhibition of c-di-GMP biosynthesis, chemical compounds positive in the CR assay are tested for their ability to inhibit biofilm formation and in a reporter gene assay which monitors expression of curli-encoding genes as a function of DGC activity. Screening of a chemical library using the described approach allowed us to identify sulfathiazole, an antimetabolite drug, as an inhibitor of c-di-GMP biosynthesis. Sulfathiazole probably affects c-di-GMP biosynthesis in an indirect fashion rather than by binding to DGCs; however, sulfathiazole represents the first example of drug able to affect biofilm formation by interfering with c-di-GMP metabolism
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
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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