1,721,057 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
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
Mechanisms of Persister Cell Formation in Salmonella enterica subsp. enterica serovar Typhimurium
Full text linkPersister cells are drug-tolerant bacteria that can survive lethal antibiotic exposure despite lacking genetic resistance mechanisms. Various pathways are involved in the formation of persisters, including the energy balance of the bacteria.To test the involvement of ATP in the formation of persister cells after treatment with antibiotics, the ATP-synthase was deleted in Salmonella Typhimurium. However, the resulting reduced ATP concentration did not increase the tolerance of the mutant, on the contrary, treatment with ciprofloxacin, a fluoroquinolone, resulted in fewer persistent cells compared to the corresponding wild type.
Furthermore, the involvement of prophages in terms of persister cell formation of Salmonella Typhimurium was investigated. Deletion of the endogenous prophages, designated Gifsy-1, Gifsy-2, Gifsy-3, and ST63B, resulted in slowed initial killing and increased formation of persistent cells after the bacteria were exposed to ciprofloxacin. In particular, Gifsy-1 and the prophage-mediated lysis process were largely responsible for the reduced formation of persister cells in the prophage-carrying wild type.Persisterzellen sind Antibiotika-tolerante Bakterien, die eine Behandlung mit Antibiotika, trotz fehlender Resistenzmechanismen, überleben. Verschiedene Mechanismen wurden bis heute beschrieben, wie Persisterzellen sich der tödlichen Wirkung von Antibakteriziden wieder setzen können. Unter anderen spielen die Oxidative Stress-, SOS-, und stringente Antwort eine wichtige Rolle sowie der Energiehaushalt der Bakterien zum Zeitpunkt der Behandlung mit Antibiotika. Um die Wichtigkeit von ATP bezüglich der Persisterzellbildung zu untersuchen, wurde in den Gramm-negativen Bakterium Salmonella Typhimurium, die ATP-Synthase deletiert, die signifikant zur Bildung von ATP beiträgt. Die Deletion des atp Operons führt zur einer verringerten ATP-Konzentration, jedoch nicht, wie zuvor berichtet, zur mehr Persisterzellen nach Behandlung mit dem Fluoroquinolon Ciprofloxacin. Weitere Untersuchungen zeigten, dass die Deletion der ATP-Synthase zur einer erhöhten Menge an NADH führt. Das wiederrum stimuliert die respiratorische Aktivität und führt zur einer erhöhten Bildung von reaktiven Sauerstoffradikalen, die die Empfindlichkeit der Mutante gegenüber Ciprofloxacin verstärkt.
Ein weiterer Bestandteil dieses Projektes war, die Beteiligung von endogenen Prophagen bezüglich der Persisterzellbildung zu untersuchen. Salmonella Typhimurium verfügt über ein diverses Repertoir an Prophagen, das unter anderem Fels-1, Fels-2, Gifsy-1, Gifsy-2, Gifsy-3 und ST64B einschließt. Um den Effekt der Prophagen zu studieren, wurden Gifsy-1, Gifsy-2, Gifsy-3 und ST64B aus dem Chromosomen deletiert. Die anschließende Behandlung mit Ciprofloxacin führte zu einer verlangsamten Abtötung des phagenfreien Stammes sowie zur mehr Persisterzellen. Weitere Untersuchungen zeigten, dass vor allem Gifsy-1 durch Ciprofloxacin induziert wird und zur Lyse des Wirtes führt. Die Antibiotika-induzierte Lyse durch die Prophagen reduziert daher die Persisterzellbildung in dem Wildtyp und macht ihm empfindlicher gegenüber DNA-schädigten Antibakteriziden
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
The Role of Salmonella Pathogenicity Island-2 (SPI-2) in the Course of Neonatal Non-typhoidal Salmonella Infections
Full text linkAs a major cause of infectious diarrheal diseases, non-typhoidal Salmonella (NTS), such as S. enterica subsp. enterica serovar Typhimurium, are of global health concern for both human and veterinary medicine. Besides causing usually self-limiting gastroenteritis in immunocompetent adult individuals, infection of neonates with this pathogen can induce invasive and potentially life-threatening conditions. Invasive infection caused by NTS are predominantly observed in developing countries with poor hygiene standards, where the pathogen is frequently isolated from cases of neonatal sepsis and meningitis. The pathogenicity of Salmonella is conferred by certain virulence factors encoded on chromosomal regions acquired by horizontal gene transfer, called Salmonella pathogenicity islands (SPIs). Delivery of effector proteins of SPI-1 and SPI-2 into the host cell is enabled via own type three secretion systems (T3SSs). The role of SPI effectors in host-pathogen interactions has been extensively studied in vitro and it is widely accepted that SPI-2 is crucial for the establishment of an intracellular compartment, the Salmonella-containing vacuole (SCV), which allows the bacteria to survive and replicate inside the host cell. Besides this, the translocated effector proteins allow the pathogen to modulate and manipulate the host cell system in various respects. Knowledge about effector contribution and their distinct role in pathogenesis of invasive NTS infections in vivo is rather scant. Therefore, we applied the neonate mouse model, which, in contrast to the commonly used streptomycin adult mouse infection model, allows the formation of SCVs inside infected enterocytes, followed by mucosal barrier penetration and subsequent bacterial dissemination without previous antibiotic depletion of the resident gut microbiota. In this study, we used this infection model to extend our knowledge on the role of individual SPI-2 effector proteins in establishment and progression of systemic Salmonella infections in the neonate host. Oral infection of neonates with wildtype and ΔSPI-2 Salmonella resulted in similar bacterial loads of the gastrointestinal tract, but re-isolation rates of SPI-2-deficient mutants from systemic organs, such as liver and spleen, and expression of pro-inflammatory cytokines were significantly decreased. Interestingly, in contrast to the general understanding of SPI-2 as prerequisite for SCV formation in vitro, mutants were able to establish and maintain SCVs in neonatal intestinal enterocytes. In fact, SPI-2-deficient bacteria grow to high numbers inside SCVs, nonetheless, like in the adult host, are attenuated in virulence and hampered in disease progression. The establishment of an SCV is not only feasible in the absence of the SPI-2 effector protein subset, but also without the host adaptor protein myeloid differentiation primary response 88 (MYD88). The observation of enlarged SCV formation in the absence of SPI-2, however, is strictly limited to the neonatal period. This is due to the immature intestinal tract constituting a unique environment with pending epithelial renewal on the one hand, whereas constant nutrient supply is ensured by fusion of the bacterial vacuole with transport vesicles on the other hand. By evaluating isogenic single SPI-2 effector protein mutants, we detected that SPI-2 effectors enabling interaction with the host cell microtubule network and positioning of the SCV inside the host cell partly phenocopy the SPI-2 dependent phenotype in vivo. Results achieved in this study suggest that depletion of SPI-2 effectors involved in the interaction with the host cell transport machinery still allows bacterial replication in the neonate intestine. However, the absence of these effectors prevents SCV transmigration from the apical to the basolateral side of the enterocytes. Mutants are therefore “stuck” inside their SCVs, which ultimately diminishes systemic spread to liver and spleen and complete pathogenesis of Salmonella in vivo. Thereby, SPI-2 effector proteins are needless in terms of early steps in NTS pathogenesis in the neonate host, but become urgent for the pathogen in order to overcome the epithelial barrier and achieve systemic dissemination
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
