1,720,973 research outputs found
The capsular polysaccharide Vi from Salmonella typhi: synthesis and molecular dynamic simulations of short analogue fragments
No full textVi capsular polysaccharide (Vi antigen) is the virulence factor of Salmonella enterica serovar typhi, the causative agent of typhoid fever in humans. It is a linear homopolymer made up of alpha-(1→4)-linked N-acetyl galactosaminuronic acid with a 60-70% O-acetylation at C-3. Vaccination with purified Vi antigen from Salmonella typhi can protect against typhoid fever, although many aspects of the mechanism of action have yet to be established. It has been demonstrated that the immunogenicity of Vi is strongly related to the content of O-acetyl groups and seems not related to the presence of the carboxyl groups. In fact, the acetate groups dominate the molecular surface of the polysaccharide and confer hydrophobic properties to it, probably shielding the carboxylic groups from interaction with other molecules, even if only partial 3-O-acetylation seems necessary to maintain the flexibility of the molecules. Being interested in the study of the role of the negative charge of the Vi biopolymer on the biological activity, we have planned the preparation of analogues where the carboxylic group has been substituted with a pH-independent ionizable group, i.e. the sulfate group. The sulfate group has been selected after preliminary investigations through molecular dynamics simulations on a hexasaccharide Vi antigen fragment, that showed similarities between the conformational behavior of the natural antigen and the sulfate analogue, where the galacturonic residues have been replaced with 6-O-sulfo-galactoses.
Herein we will report our results on the conformational analysis and the stereoselective synthesis of Vi antigen sulfated-analogue fragments
Role for irrigation and debridement in periprosthetic infections
No full textIrrigation and debridement (I&D) has been described as a possible option to eradicate early postoperative periprosthetic hip and knee infections, as well as late, acute, and hematogenous ones. Still, the literature fails to uniquely assess the effectiveness of this procedure and often provides conflicting evidence. To reconcile this difference, a systematic review of the available literature from 1970 to 2013 was undertaken. Fifteen articles, for a total of 796 patients, met the inclusion criteria; the average success rate was 44.9 and 52% after a single or repeated I&D procedures, respectively, at an average of 4 years follow-up. Despite the methodological differences and the heterogeneity of the material reviewed, this study demonstrates that this procedure only attains a relatively low success rate of infection eradication, depending on when patients are selected for surgical intervention according to the timeframe of their symptoms
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
- …
