1,720,980 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
Summarizing probe intensities of Affymetrix GeneChip 3' expression arrays taking into account day-to-day variability
No full textVariations 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
Biochemical bases of the interaction of the human basic fibroblast growth factor with glycosaminoglycans: new insights from trypsin digestion studies
No full textHeparins from bovine mucosa and lung, and chemically modified
heparins were assayed for their capacity to: (i) protect human
recombinant basic fibroblast growth factor (bFGF) from tryptic
cleavage; (ii) prevent 1251-bFGF binding to heparan sulphate
proteoglycans present in the extracellular matrix and on the cell
surface of fetal bovine aortic endothelial GM 7373 cell cultures;
(iii) affect 1251-bFGF binding to high-affinity tyrosine kinase
FGF receptors present on the cell membrane of GM 7373 cells;
(iv) inhibit the mitogenic activity exerted by bFGF in the same
cells. The results demonstrate thatthe potency shown by mucosal
heparins in the different assays is a direct function of size, verylow-
molecular-mass heparin (2.0 kDa) being significantly less
effective on a molar basis than unfractionated heparin (13.6 kDa).
Increased flexibility of the backbone structure, as observed in
reduced/oxidized heparins of different size, does not affect the
capacity of the polysaccharide to interact with bFGF. In contrast,
selective 2-O-desulphation, but not 6-O-desulphation, drastically
reduced the capacity of heparin to protect bFGF from proteolytic
cleavage, to affect its interaction with low- and high-affinity sites,
and to inhibit its mitogenic activity. Two preparations of bovine
lung heparin, differing in molecular mass, were as effective as
mucosal heparin in the bFGF-tryptic-digestion assay and the
endothelial-cell proteoglycan-binding assay, but they were highly
inefficient at inhibiting the capacity of bFGF to interact with its
tyrosine kinase receptors. Bovine lung heparins were also less
effective than mucosal heparin as bFGF antagonists in GM
7373-cell-proliferation assays. N-Desulphated/N-acetylated
bovine lung heparin retained only a significant capacity to
protect bFGF from tryptic cleavage. The results demonstrate
that different chemical features of the heparin molecule, including
decrease in molecular mass, selective desulphation, disaccharide
composition and clustering, affect differently the capacity of the
glycosaminoglycan to interact with bFGF and to influence its
biological behaviour in different assays in vitro and in endothelial
cell cultures. Our findings should aid the design of synthetic
oligosaccharides aimed at improving the. bioavailability of bFGF
when administered in vivo as a therapeutic agent
A six-amino acid deletion in basic fibroblast growth factor dissociates its mitogenic activity from its plasminogen activator-inducing capacity.
No full textA recombinant deletion mutant of the 155-amino acid form of human basic fibroblast growth factor (bFGF), lacking amino acid residues 27-32 (Lys-Asp-Pro-Lys-Arg-Leu), was expressed in Escherichia coli and purified to homogeneity by heparin-Sepharose affinity chromatography. When maintained in the presence of an equimolar concentration of soluble heparin, the bFGF mutant (M1-bFGF) is as potent as bFGF in stimulating cell proliferation in normal and transformed fetal bovine aortic endothelial cells, in adult bovine aortic endothelial cells, and in NIH 3T3 fibroblasts. However, under the same experimental conditions, M1-bFGF is at least 100 times less efficient than bFGF in stimulating plasminogen activator (PA) production in endothelial cells, as assayed by chromogenic PA assay, SDS/PAGE zymography, and Northern blot analysis of urokinase-type PA mRNA. In the presence of heparin, M1-bFGF binds to bFGF plasma membrane receptors present on endothelial cells in a manner undistinguishable from bFGF. It also induces the same tyrosine phosphorylation pattern when added to NIH 3T3 cells. The data suggest that the PA-inducing activity of bFGF may depend upon a functional domain that differs from those involved in the mitogenic activity of the growth factor and that the binding of bFGF to its plasma membrane receptor may not be sufficient to induce urokinase-type PA production in endothelial cells
Non-parametric MANOVA methods for detecting differentially expressed genes in RT-PCR experiments
No full textRT-PCR is a quantitative technique of molecular biology used to amplify DNA sequences starting from a sample of mRNA. RT-PCR is typically used to explore gene expression variation across groups of treatment.
Because of the non-normal distribution of data, various authors have proposed nonparametric methods based on the MANOVA approach to deal with this problem. These methods, based on the use of distances (Anderson et al.) and of the use of the medians instead of means (Xu et al.) allow to explore patterns of differential gene expression via global F-ratio test obtained through permutations and subsequent analysis of contrasts.
A non-parametric test for multiple univariate comparisons is then used to evaluate which genes are likely to be differentially expressed across groups.
Results of a study involving 30 mice assigned to one control group and to 4 different treatments are presented. An effect of treatment on gene expression is detected by both methods, with good agreement also with respect to the pre-selected multiple comparisons.
These results are potentially useful to draw out new biological hypothesis to be verified in following designed studies.
Future research will be focused on comparison of such methods with classical strategies for analysing RT-PCR data, to better evaluate their advantages and drawbacks; moreover, work will also concentrate on extending such methods to doubly multivariate design, a context often arising in biological data
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