1,720,965 research outputs found
Evaluation of the efficiency of an assay procedure for gangliosides in human serum
No full textAn efficiency assessment of a ganglioside assay procedure was carried out on human serum gangliosides from healthy subjects of different sex and age. The analysis of the gangliosides, extracted with chloroform/methanol and purified by lipid partitioning, ion exchange column chromatographic separation and desalting procedures as described by Senn et al. (1989) Eur J Biochem 181: 657-62, was performed by HPTLC followed by densitometric quantification. The yield of the procedure, expressed as radioactivity recovery, was determined by adding GM3 ganglioside, tritium labelled at the sialic acid acetyl group and at the C3 position of sphingosine, to the lyophilized serum or by associating it with the serum lipoproteins. Tn spite of the fact that the extraction and purification procedures were performed exactly as described we found the radioactivity recovery to be variable (25-50%) and much lower than that proposed. Much of the radioactivity was found in the organic phase after lipid partitioning, whilst all the ganglioside purification steps led to some further loss. After the introduction of some modifications to the procedure the recovery improved, reaching 67-79%. The analyses on 33 samples of 5 ml showed a human serum ganglioside content of about 10 nmol ml(-1) (as corrected for the recovery), and confined that GM3 ganglioside is the main component of the total serum ganglioside mixture
Activity of 3-ketosphinganine synthase during differentiation and aging of neuronal cells in culture
No full textChanges in the enzyme 3-ketosphinganine synthase activity in rat cerebellar granule cells in culture were studied during differentiation and aging. The enzyme activity with palmitoyl-CoA and stearoyl-CoA, precursors of, respectively, C18-sphinganine and C20-sphinganine, was studied on the total cell homogenate using radioactive serine. The enzyme assay was performed by thin-layer chromatography (TLC) separation of the enzyme reaction mixture, and the resultant radioactive 3-ketosphinganine was identified by chromatographic comparison with a chemically synthesized 3-ketosphinganine, and quantified by determination of the TLC radioactivity distribution on the basis of the radioactivity content of cell lipid extract that was determined by scintillation counting. Using palmitoyl-CoA, the enzyme activity progressively increased from 40 to 54 pmol of 3-ketosphinganine/mg cell DNA per min in the first 8 days and then progressively decreased, and was 39 pmol of C18-(3-ketosphinganine)/mg cell DNA per mill at day 22 in culture. For stearoyl-Coh the enzyme activity was very low at day one and then increased to a constant value of about 15 pmol of C20-(3-ketosphinganine) /mg cell DNA per min. These results are in good agreement with the finding that the ganglioside species that contain C18-sphingosine increase during cell differentiation and remain constant during cell aging, while the ganglioside species that contain C20-sphingosine continuously increase during both cell differentiation and aging
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
