1,721,102 research outputs found
Purification and properties of the Mycobacterium smegmatis mc2155 β-lactamase
No full textThe β-lactamase of Mycobacterium smegmatis mc2155 has been purified to protein homogeneity. Its N-terminal sequence and catalytic properties are similar to those of the β-lactamase produced by Mycobacterium fortuitum D316 and establish this new enzyme as a member of molecular class A
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
Mycobacterium tuberculosis
No full textTese de mestrado em Biologia Molecular e Genética apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2007The Beijing/W family of Mycobacterium tuberculosis represents a global threat in tuberculosis control. It has been frequently associated with drug resistance and its wide distribution suggests that these strains may have selective advantages over others. On the present study a collection of Beijing/W strains isolated in different countries was analyzed under the genetic markers: Large Sequence Polymorphisms (LSPs) and Single Nucleotide Polymorphisms (SNPs). Through a Multiplex-PCR isolates were tested for the presence or absence of the LSPs, described by a previous study for the Beijing/W family (RD105, RD181, RD150, RD142). The analysis of these regions proved to be very useful for defining and broadly subdivide the Beijing/W family in four groups. Furthermore, it provided a support for selection of representative isolates for the further study of other markers like SNPs in recently identified polymorphic DNA repair, recombination and replication (3R) genes. Selected 3R genes were sequenced for representative Beijing/W isolates to search for variations and comparative analysis with M.tuberculosis H37Rv identified SNPs for all genes. Almost half corresponded to not previously described SNPs and a large proportion seemed specific to Beijing/W strains. SNPs were much more informative than LSPs distinguishing twenty-four groups for which a hypothetic phylogenetic network was constructed. Phylogenetic relations originated by SNPs were found to be congruent with the ones originated by LSPs and also with previous studies on mutT2, muT4 and ogt putative DNA repair genes. Analysis according to geographic origin of isolates suggested that the collection used might be representative of the Beijing/W family. Certain genes were found to be more polymorphic than others with the accumulation of several non-synonymous SNPs (nsSNPs) that may potentially affect the function of the protein. Altered function in proteins involved in such important mechanisms in genome dynamics and stability might be associated with mutator phenotypes strains having high mutation rates in Beijing/W strains, as previously suggested. This might explain their higher adaptability and frequent association with resistance to antibiotics. Overall, this study provided useful information that, although may need to be validated using a larger set of isolates, it could be the start point for several future studies. It may contribute to clarify the role of the Beijing/W family in the tuberculosis pandemic.Resumo alargado disponível em portuguê
Mycobacterium tuberculosis
No full textTese de mestrado em Biologia Molecular e Genética apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2007The Beijing/W family of Mycobacterium tuberculosis represents a global threat in tuberculosis control. It has been frequently associated with drug resistance and its wide distribution suggests that these strains may have selective advantages over others. On the present study a collection of Beijing/W strains isolated in different countries was analyzed under the genetic markers: Large Sequence Polymorphisms (LSPs) and Single Nucleotide Polymorphisms (SNPs). Through a Multiplex-PCR isolates were tested for the presence or absence of the LSPs, described by a previous study for the Beijing/W family (RD105, RD181, RD150, RD142). The analysis of these regions proved to be very useful for defining and broadly subdivide the Beijing/W family in four groups. Furthermore, it provided a support for selection of representative isolates for the further study of other markers like SNPs in recently identified polymorphic DNA repair, recombination and replication (3R) genes. Selected 3R genes were sequenced for representative Beijing/W isolates to search for variations and comparative analysis with M.tuberculosis H37Rv identified SNPs for all genes. Almost half corresponded to not previously described SNPs and a large proportion seemed specific to Beijing/W strains. SNPs were much more informative than LSPs distinguishing twenty-four groups for which a hypothetic phylogenetic network was constructed. Phylogenetic relations originated by SNPs were found to be congruent with the ones originated by LSPs and also with previous studies on mutT2, muT4 and ogt putative DNA repair genes. Analysis according to geographic origin of isolates suggested that the collection used might be representative of the Beijing/W family. Certain genes were found to be more polymorphic than others with the accumulation of several non-synonymous SNPs (nsSNPs) that may potentially affect the function of the protein. Altered function in proteins involved in such important mechanisms in genome dynamics and stability might be associated with mutator phenotypes strains having high mutation rates in Beijing/W strains, as previously suggested. This might explain their higher adaptability and frequent association with resistance to antibiotics. Overall, this study provided useful information that, although may need to be validated using a larger set of isolates, it could be the start point for several future studies. It may contribute to clarify the role of the Beijing/W family in the tuberculosis pandemic.Resumo alargado disponível em portuguê
Mycobacterium tuberculosis
No full textTese de mestrado em Biologia Molecular e Genética apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2007The Beijing/W family of Mycobacterium tuberculosis represents a global threat in tuberculosis control. It has been frequently associated with drug resistance and its wide distribution suggests that these strains may have selective advantages over others. On the present study a collection of Beijing/W strains isolated in different countries was analyzed under the genetic markers: Large Sequence Polymorphisms (LSPs) and Single Nucleotide Polymorphisms (SNPs). Through a Multiplex-PCR isolates were tested for the presence or absence of the LSPs, described by a previous study for the Beijing/W family (RD105, RD181, RD150, RD142). The analysis of these regions proved to be very useful for defining and broadly subdivide the Beijing/W family in four groups. Furthermore, it provided a support for selection of representative isolates for the further study of other markers like SNPs in recently identified polymorphic DNA repair, recombination and replication (3R) genes. Selected 3R genes were sequenced for representative Beijing/W isolates to search for variations and comparative analysis with M.tuberculosis H37Rv identified SNPs for all genes. Almost half corresponded to not previously described SNPs and a large proportion seemed specific to Beijing/W strains. SNPs were much more informative than LSPs distinguishing twenty-four groups for which a hypothetic phylogenetic network was constructed. Phylogenetic relations originated by SNPs were found to be congruent with the ones originated by LSPs and also with previous studies on mutT2, muT4 and ogt putative DNA repair genes. Analysis according to geographic origin of isolates suggested that the collection used might be representative of the Beijing/W family. Certain genes were found to be more polymorphic than others with the accumulation of several non-synonymous SNPs (nsSNPs) that may potentially affect the function of the protein. Altered function in proteins involved in such important mechanisms in genome dynamics and stability might be associated with mutator phenotypes strains having high mutation rates in Beijing/W strains, as previously suggested. This might explain their higher adaptability and frequent association with resistance to antibiotics. Overall, this study provided useful information that, although may need to be validated using a larger set of isolates, it could be the start point for several future studies. It may contribute to clarify the role of the Beijing/W family in the tuberculosis pandemic.Resumo alargado disponível em portuguê
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
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