1,720,963 research outputs found
Quantification of incorporation of [15N]ammonia into plasma amino acids and urea
No full textThe incorporation of 15N into individual plasma amino acids and urea was quantified in five human subjects who received 15NH4Cl either orally or intravenously for 6 h. After oral tracer administration, the highest enrichment was achieved by arginine, followed by urea and glutamine; distribution of 15N within glutamine was 55% amide and 45% amino N. Glutamine achieved the highest enrichment after the intravenous administration of tracer, with a distribution of 92% amide and 8% amino N. The relative distribution pattern of 15N incorporation was quantified from the rate at which 15N initially appeared in each plasma component. Amino acids (especially arginine, glutamine, and glutamate) accounted for greater than one-half (54%) of the orally administered tracer that was initially recovered in plasma components, compared with 46% initial appearance for urea; for the intravenous tracer, amino acids accounted for 78% of initial appearance of tracer compared with 22% for urea. Our results highlight the involvement of the splanchnic bed in the utilization of orally administered ammonia (preferential incorporation of oral tracer into arginine, urea, glutamate, and the amino N of glutamine) in contrast to the preferential incorporation of systemically administered ammonia into the amide N of glutamine and alanine
Measurement of 15N enrichment in multiple amino acids and urea in a single analysis by gas chromatography/mass spectrometry
No full textA precise and accurate procedure to measure the 15N isotopic enrichment of 18 common plasma amino acids and singly (15N1) and doubly (15N2) labeled urea in a single analysis by selected ion monitoring electron impact ionization gas chromatography/mass spectrometry analysis is presented. The choice of tert-butyldimethylsilyl derivatives allowed the enrichments in the amide and amino nitrogens of glutamine to be resolved. The ions monitored contained all the nitrogen atoms from the parent compounds except for arginine, which lost one guanidino nitrogen. Isotope ratios were determined with a coefficient of variation (within-assay precision) of 0.35% (range, 0.1-1.0%) on replicate measures averaged over all components; thus, the standard deviation associated with a nominal [m + 1]/[m + 0] isotope ratio of 0.2000 was 0.0007. The average error between measured and theoretical [m + 1]/[m + 0] isotope ratios was +0.0001 +/- 0.0086 for samples at natural abundance isotopic composition. The utility of the procedure is demonstrated by monitoring the incorporation of 15N into 18 plasma amino acids and urea during a 6 h oral administration of 15NH4Cl to a human volunteer. Highest levels of enrichment were achieved in arginine and urea, followed by glutamine. Approximately 80% of the label in glutamine was in the amino nitrogen. Excess 15N enrichment was observed in all plasma amino acids monitored with the exception of the essential amino acids phenylalanine, lysine and histidine. This method will facilitate the measurement of isotopic enrichment of multiple amino acids by a single analysis when it is necessary to monitor multiple stable-isotopically labeled amino acids in studies of amino acid and protein metabolic kinetics
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
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
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