1,721,252 research outputs found
Discrimination between organic and conventional flour using compound-specific amino acid δ15N analysis
No full textThe application of nitrogen stable isotope ratio 15N/14N analysis to discriminate between organic and conventional cultivation is based on the fact that the different types of fertilizer used on the soil influence the nitrogen isotopic composition of crops. The δ15N value of plants grown with the use of fertilizers of animal origin and vegetable compost is statistically higher than for those grown using mineral fertilizers. δ15N values can therefore be used as an indicator of organic or conventional management systems. Traditional techniques rely on measurement of bulk samples, but emerging methods using individual chemical compounds provide a means of obtaining a more in-depth understanding.
In this work we present a study of compound-specific nitrogen isotope analysis of amino acids to discriminate between organically and conventionally grown plants. Amino acids are indeed the dominant nitrogen-bearing biomolecules in plants and the pattern of isotopic fractionation during synthesis of these compounds records a range of information about the growth environment, such as the form of assimilable N available in the soil.
Our investigation was based on flour samples grown with synthetic nitrogen fertilizer animal manure and green manure from atmospheric nitrogen fixing legumes. The measurement of amino acid δ15N values after protein hydrolysis and N-acetylisopropyl derivatization was carried out using gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS).
Our results demonstrate that the molecular amino acid δ15N isotope profile is different in samples, depending on the relative source of nitrogen
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
Photorespiratory NH4+ production in leaves of wild-type and glutamine synthetase 2 antisense oilseed rape
No full textExposure of oilseed rape (Brassica napus) plants to increasing leaf temperatures between 15 degreesC and 25 degreesC increased photorespiratory NH(4)(+) production from 0.7 to 3.5 mumol m(-2) s(-1). Despite the 5-fold increase in the rate of NH(4)(+) production, the NH(4)(+) concentration in root and leaf tissue water and xylem sap dropped significantly, whereas that in the leaf apoplastic fluid remained constant. The in vitro activity of glutamine synthetase (GS) in both leaves and roots also increased with temperature and in all cases substantially exceeded the observed rates of photorespiratory NH(4)(+) production. The surplus of GS in oilseed rape plants was confirmed using GS2 antisense plants with 50% to 75% lower in vitro leaf GS activity than in the wild type. Despite the substantial reduction in GS activity, there was no tendency for antisense plants to have higher tissue NH(4)(+) concentrations than wild-type plants and no overall correlation between GS activity and tissue NH(4)(+) concentration was observed. Antisense plants exposed to leaf temperatures increasing from 14 degreesC to 27 degreesC or to a trifold increase in the O(2) to CO(2) ratio did not show any change in steady-state leaf tissue NH(4)(+) concentration or in NH(3) emission to the atmosphere. The antisense plants also had similar leaf tissue concentrations of glutamine, glycine, and serine as the wild type, whereas glutamate increased by 38%. It is concluded that photorespiration does not control tissue or apoplastic levels of NH(4)(+) in oilseed rape leaves and, as a consequence, that photorespiration does not exert a direct control on leaf atmosphere NH(3) fluxes
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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