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Natural history of hepatitis B virus infection and disease
No full textThe natural history of hepatitis B virus (HBV) infection is complex and variable and is greatly influenced by the age at infection –the younger the age the higher the probability of chronicity– the level of HBV replication and host immune status. Chronic hepatitis B
is usually characterized by an early replicative phase with hepatitis B e antigen (HBeAg)positivity, high serum HBV-DNA levels (> 105 copies/ml) and normal serum alanine
aminotransferase (ALT) (HBeAg-positive chronic hepatitis in the “immunotolerant” phase) or raised serum ALT and active hepatitis (HBeAg-positive chronic hepatitis in the “immunoactive”
phase) and a late inactive phase with HBeAg seroconversion, low or undetectable serum HBV-DNA, and liver disease remission (inactive carrier state). Another form of chronic hepatitis B is characterized by HBeAg negativity, detectable serum HBV-DNA
levels (suggested threshold > 104 copies/ml) and active hepatitis due to HBV variants not expressing HBeAg (HBeAg-negative chronic hepatitis). HBeAg-negative chronic hepatitis
represents a late phase of chronic HBV infection and its prevalence is increasing throughout the world. Chronic hepatitis B is associated with serious complications, including cirrhosis, hepatic decompensation and hepatocellular carcinoma (HCC). The incidence of cirrhosis ranges from 0.5 per 100 person years in HBeAg-positive chronic hepatitis in the immunotolerant phase to 2 to 5 per 100 person years in HBeAg-positive chronic hepatitis
in the immunoactive phase, but may be as high as 8 to 10 in HBeAg-negative chronic hepatitis. The incidence of HCC appears to vary geographically and increases with the severity of liver disease (0.02 to 1.0 per 100 person years in carriers without cirrhosis at baseline to 2 to 3 per 100 person years in cirrhotic patients). The five-year mortality rate is about 15% for patients with compensated cirrhosis and 65% to 85% following decompensation. HCC and liver failure are the main causes of death. Viral-related factors (level and persistence of HBV replication, emergence of viral mutants, HBV genotype, viral
coinfections), host-related factors (sex, age at infection, age at diagnosis, stage of liver disease at presentation, recurrent hepatitis flares, sustained aminotransferase normalization),
and environmental factors (alcohol abuse, smoking and dietary carcinogens) may all be important determinants of the outcome of the diseas
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
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