1,721,090 research outputs found
Divergence of a strain of Pseudomonas aeruginosa during an outbreak of ovine mastitis
No full textAbstract not availableElli A. Wright, Valeria Di Lorenzo, Claudia Trappetti, Manuele Liciardi, Germano Orru, Carlo Viti, Christina Bronowski, Amanda J. Hall, Alistair C. Darby, Marco R. Oggioni, Craig Winstanle
A Non-Linear Deterministic Model for Regulation of Diauxic Lag on Cellobiose by the Pneumococcal Multidomain Transcriptional Regulator CelR
No full textWhen grown on glucose and beta-glucosides, S. pneumoniae shows sequential use of sugars resulting in diauxic growth
with variable time extent of the lag phase separating the biphasic growth curve. The pneumococcal beta-glucoside uptake
locus containing the PTS transporter spr0276-82, is regulated by a multi-domain transcriptional regulator CelR. In this work,
we address the contribution of phosphorylation of the phosphorylable cysteine in the EIIB domain of CelR to diauxic lag.
Utilising site-directed mutagenesis of the phosphorylable amino acids in the EIIB and EIIA domains of CelR, we show that
the EIIB domain activation is linked to the duration of the lag phase. Analysis of mutants for other PTS systems indicates that
a second beta-glucoside PTS (spr0505), not able to support growth on cellobiose, is responsible for the lag during diauxic
growth. A mathematical model of the process is devised together with a nonlinear identification procedure which provides
model parameter estimates characterizing the single phases of bacterial growth. Parameter identification performed on
data recorded in appropriate experiments on mutants allows for establishing a relationship between a specific model
parameter, the EIIB domain and the time extent of the diauxic lag. The experimental results and the related insights
provided by the mathematical model provide evidence that the conflicting activation of the CelR regulator is at the origin of
the lag phase during sequential growth on glucose and cellobiose. This data is the first description of diauxic lag regulation
involving two PTS and a multidomain regulator and could serve as a promising approach for studying the S. pneumoniae
growth process on complex carbon sources as possibly encountered in the human host
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
Extracellular matrix formation enhances the ability of streptococcus pneumoniae to cause invasive disease
Full text linkExtent: 17p.During infection, pneumococci exist mainly in sessile biofilms rather than in planktonic form, except during sepsis. However, relatively little is known about how biofilms contribute to pneumococcal pathogenesis. Here, we carried out a biofilm assay on opaque and transparent variants of a clinical serotype 19F strain WCH159. After 4 days incubation, scanning electron microscopy revealed that opaque biofilm bacteria produced an extracellular matrix, whereas the transparent variant did not. The opaque biofilm-derived bacteria translocated from the nasopharynx to the lungs and brain of mice, and showed 100- fold greater in vitro adherence to A549 cells than transparent bacteria. Microarray analysis of planktonic and sessile bacteria from transparent and opaque variants showed differential gene expression in two operons: the lic operon, which is involved in choline uptake, and in the two-component system, ciaRH. Mutants of these genes did not form an extracellular matrix, could not translocate from the nasopharynx to the lungs or the brain, and adhered poorly to A549 cells. We conclude that only the opaque phenotype is able to form extracellular matrix, and that the lic operon and ciaRH contribute to this process. We propose that during infection, extracellular matrix formation enhances the ability of pneumococci to cause invasive disease.Claudia Trappetti, Abiodun D. Ogunniyi, Marco R. Oggioni and James C. Pato
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
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