1,721,306 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
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
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
Virulence aspects of Staphylococcus epidermidis: biofilm formations and Poly-N-Acetyl-Glucosamine production
Get PDFTese Doutoramento em Engenharia Química e BiológicaStaphylococcus epidermidis and other Staphylococci are now well established as major nosocomial pathogens associated with infections of indwelling medical devices. The major virulence factor of these organisms is their ability to adhere to devices and form biofilms. Biofilms are complex microbial communities wherein bacteria acquire different characteristics from their planktonic counterparts, like enhanced resistance to antibiotics and host defenses. The work described in this thesis aimed at evaluating the ability of adhesion and biofilm formation of several clinical isolates of Staphylococci as well as the phenotypic alterations triggered by the sessile mode of growth. The determination of the role of Poly-N-Acetyl-Glucosamine (PNAG), a major constituent of the biofilm matrix, in S. epidermidis pathogenesis was also a goal of the described work. Some experimental approaches were developed or optimized in order to assess initial adhesion, biofilm formation and PNAG production with accurate and expedite methods. According to the results, initial adhesion and biofilm maturation are two distinct phenomena, and may influence virulence differently. Initial adhesion was found to be dependent on the surface composition, being hydrophobic surfaces more prone to bacterial adhesion. Biofilm formation was not so strongly affected by the substratum surface properties. It was also demonstrated that sub-inhibitory concentrations of antibiotics differently influence initial adhesion and biofilm formation abilities. Additionally, biofilms formed in the presence of sub-inhibitory concentrations of antibiotics exhibit alterations in their structures and matrix compositions and the biofilm cells acquire enhanced resistance to antibiotics. The results also revealed that S. epidermidis biofilm cells are more resistant to antibiotics that target cell wall synthesis but fairly susceptible to antibiotics that target RNA and protein synthesis, when compared to their equivalent planktonic populations. Biofilm cells proved to be more resistant to the lytic action of phage K than their exponentially grown planktonic counterparts, possibly due to the lower growth rate of biofilm bacteria. Furthermore, it was also demonstrated that biofilm cells are more resistant to phagocytosis (evaluated in vitro and in vivo), probably due to the high levels of PNAG expression, since PNAG is a known inhibitor of phagocytosis. The role of PNAG on Staphylococci virulence was also established by the direct relation between biofilm formation ability and level of PNAG expression. The molecular studies of PNAG production demonstrated that the icaB gene, present on the intercellular adhesion locus (ica), plays an important role in the virulence of Staphylococcus spp, mediating PNAG anchorage to the cell surface or release into the extracellular media, acting as a possible decoy to the immune system. This newly described mechanism highlighted the role of PNAG in biofilm resistance to the immune system. Finally, and focusing on the role of PNAG as a target to vaccine development, several pathogenic genera were screened for PNAG production. The fact that an immunological similar polysaccharide to the Staphylococcal PNAG was detected on the cell surface of several strains of E. coli, Yersinia spp. and Bordatela spp, opens the possibility for the development of a broad vaccine against some of the major human pathogens.A espécie Estafilococos epidermidis assim como outras espécies de Estafilococos é actualmente reconhecida com uma importante espécie nosocomial patogénica associada a um grande número de infecções relacionadas com a utilização de implantes médicos invasivos. A capacidade que esta espécie apresenta para aderir a superfícies e para formar biofilmes é considerada um dos factores de virulência preponderantes. Os biofilmes são estruturas complexas que conferem às células bacterianas resistência aos antibióticos e às defesas naturais do organismo. O trabalho descrito nesta dissertação teve como objectivo principal o estudo da capacidade de adesão e formação de biofilmes de várias estirpes clínicas de Estafilococos bem como a determinação das alterações fisiológicas induzidas pelo fenótipo de biofilme e a importância da segregação do polissacárido poli-N-acetilglucosamina (PNAG), um constituinte importante do biofilme. Os estudos conduzidos e aqui descritos pretendem explicar as implicações das características fenótipicas dos biofilmes de Estafilococos na virulência desta espécie. Foi necessário desenvolver um conjunto de metodologias que permitem de forma expedita e fidedigna estudar a capacidade de adesão, de formação de biofilme, bem como de quantificação de PNAG. Os resultados obtidos permitiram concluir que a capacidade de adesão é dissociada da capacidade de formação de biofilme pelo que adesão e formação de biofilme devem se considerados dois fenómenos distintos. Consequentemente demonstrou-se que a composição da superfície de adesão implica o fenómeno de adesão, sendo ele mais favorável a superfícies hidrofóbicas, afectando de forma não linear a formação de biofilme. Do mesmo modo demonstrou-se que concentrações sub-inibitórias de antibióticos afectam de forma diferente a adesão a superfícies e a formação de biofilme, e verificou-se também que os biofilmes formados na presença de concentrações sub-inibitórias de antibióticos apresentam alterações na composição e estrutura da matriz e aumento de resistência a certos antibióticos. Os estudos realizados permitiram ainda concluir que os biofilmes de Estafilococos são mais resistentes à acção de antibióticos do que as células suspensas, especialmente os que actuam ao nível da síntese da parede, tendo no entanto sido susceptíveis a antibióticos que afectam a replicação de RNA e a produção de proteínas. Os biofilmes de Estafilococos mostraram-se também mais resistentes à acção lítica do bacteriófago K, possivelmente devido à baixa taxa de crescimento das células no biofilme. Também se verificou que populações de bactérias crescidas em biofilmes apresentavam maior resistência à fagocitose (avaliada in vitro e in vivo), possivelmente devido à elevada quantidade de PNAG detectada na sua superfície celular e na matriz do biofilme, visto que PNAG é um conhecido inibidor da fagocitose. Esta molécula parece ser determinante na formação dos biofilmes uma vez que biofilmes mais espessos apresentam maior quantidade de PNAG. Os estudos moleculares realizados permitiram concluir que o gene icaB, presente no operão ica, desempenha um papel crucial na virulência de Estafilococos, mediando a fixação da PNAG na superfície celular ou a libertação para o meio externo, funcionado então como uma possível defesa contra o sistema imune do hospedeiro, sendo este um novo mecanismo descrito elucidando melhor a capacidade de resistência dos biofilmes de Estafilococos ao sistema imune. A PNAG parece ser ubíqua em espécies de importância clínica, uma vez que se detectou a presença de uma molécula imunologicamente semelhante à PNAG em estirpes clínicas de Escherichia coli, Yersinia spp. e Bordatela spp. Esta descoberta poderá abrir novas perspectivas no desenvolvimento de vacinas capazes de combater diferentes agentes patogénicos.Fundação para a Ciência e aTecnologia (FCT) - SFRH/BD/8676/200
Addressing the challenges with bacterial vaginosis pharmacotherapy
Get PDF[Excerpt] 1. Introduction: The healthy female vaginal environment is a dynamic ecosystem that is commonly colonized by several lactic acid-producing bacteria, most of the genus Lactobacillus [1]. It is believed that the normal human vaginal microbiota has an important role in maintaining health, with an impact on either baby delivery or increased risks in the acquisition of sexually transmitted infections [2]. The composition of the vaginal microbiota depends on ethnicity and can change over the menstrual cycle, during pregnancy, with age, and under external stresses, such as antimicrobial treatments [3]. For reasons not yet fully understood, the dominant healthy vagina lactic acid and hydrogen peroxide-producing lactobacilli can be replaced by a complex mixture of strictly and facultative anaerobic bacteria [4]. This significant shift in the composition of the vaginal microbiome is known as bacterial vaginosis (BV). Despite being the most common dysbiosis in women of childbearing age, BV etiology is not yet fully understood, with different controversial theories being raised over the years [3]. [...]info:eu-repo/semantics/publishedVersio
Understanding microbial interactions in infectious diseases to improve diagnostic and therapeutic success
Get PDFThe human microbiome project changed the fundamental understanding of how
microorganism interact with the human host, wherein synergistic and antagonistic
interactions can be observed. Classical biomedical research focused on understanding
how bacterial-host interactions could influence disease progression. Yet less explored,
bacterial-bacterial interactions can also contribute to disease progression and to
therapeutic failure. Examples of microbial interactions leading to disease include cystic
fibrosis, dental caries or bacterial vaginosis. While the first two are currently easily
diagnosed, bacterial vaginosis presents an increased challenge, mainly because its
etiology is yet fully understood. Bacterial vaginosis is the most frequent cause of vaginal
discomfort worldwide, and is also linked to serious medical conditions, including preterm
birth and increased risk of acquisition of HIV. The bacterial interactions occurring during
bacterial vaginosis are thought to be responsible for therapeutic failure, leading to very
high recurrence rates. Despite the worldwide prevalence and the significant economic
cost, researchers havent yet identified bacterial vaginosis etiology, but current consensus
is that a polymicrobial biofilm is involved.
During this talk, I will highlight two projects wherein my research group is aiming to (i)
provide a better picture of how these bacterial species interactions enhance protection
against current and/or potential novel antimicrobial agents or (ii) using the presence of
key bacterial interactions as a mean to develop robust molecular diagnosis methods.info:eu-repo/semantics/publishedVersio
The role of Gardnerella vaginalis in mixed species biofilms occurrence in bacterial vaginosis and its prevalence in Portugal
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