1,720,958 research outputs found
Essential oil composition and variability of Hypericum perforatum from wild populations of northern Turkey
No full textContext: Hypericum perforatum L. (Guttiferae) contains many bioactive secondary metabolites including hypericins, hyperforins, and essential oil.Objective: The present study was conducted to det. the variation in compn. of essential oil in H. perforatum accessions from Turkey.Material and methods: At full flowering, aerial parts of 30 plants were collected from 10 sites of northern Turkey and assayed for essential oil components by GC-FID and GC-MS.Results: The chem. anal. revealed that the main constituents of the all analyzed samples were hydrocarbon and oxygenated sesquiterpenes such as β-caryophyllene (4.08-5.93%), γ-muurolene (5.00-9.56%), β-selinene (5.08-19.63%), α-selinene (4.12-10.42%), d-cadinene (3.02-4.94%), spathulenol (2.34-5.14%), and caryophyllene oxide (6.01-12.18%). Monoterpenes, both hydrocarbon and oxygenated, were represented by scarce amts. of α- and β-pinene, myrcene, linalool, cis- and trans-linalool oxide, and α-terpineol. Principal component anal. was also carried out and, according to the results, the first nine principal components were found to represent 100% of the obsd. variation.Discussion: The chem. variation among the populations is discussed as the possible result of different genetic and environmental factors.Conclusions: The wild populations examd. here are potentially important sources for breeding and improvement of the cultivated varieties
Morphogenetic changes in essential oil composition of Hypericum perforatum during the course of ontogenesis
No full textContext: In the past few years, an increasing interest in the volatile secondary metabolites of Hypericum perforatum L.
(Guttiferae) has been arising.
Objective: The present study is a contribution to better understand the relationship between the morphological
variations and volatile composition during the phenological cycle.
Materials and methods: Leaves at the stages of vegetative, floral budding, flowering and green capsule, buds, full
opened flowers and green capsules were assayed for essential oil (EO) components by gas chromatography-flame
ionization detector (GC-FID) and GC-mass spectrometry (MS).
Results: Significant amounts of sesquiterpenes (oxygenated 26–50% and hydrocarbons 20–40%) and oxygenated
hydrocarbons (13–38%) characterized the all analyzed samples showing peculiar fluctuations during the seven
phenological stages. Although monoterpenes were present in much lower amounts (monoterpene hydrocarbons
0.4–6%; oxygenated monoterpenes 0.8–6%) they were considered also important discrimination for several stages.
The green capsules and the full opened flowers collected at flowering stage were clearly distinguished in terms of EO
compositions from the other samples.
Discussion: For the first time, the EO composition of Turkish wild Hypericum perforatum was monitored by the
hydrodistillation of different plant organs collected at different seven stages in order to point out the modification of
target volatiles related to each phenological step.
Conclusions: Based on the EO composition monitored during these seven morphological stages by GC-MS,
principal component analysis and cluster analysis, significant metabolite modifications were observed during the
phenological cycle which involved the levels of specific volatile target compounds belonging to the chemical classes
of hydrocarbons, monoterpenes and sesquiterpenes
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
Combination of resistance to Verticillium longisporum from zero erucic acid Brassica oleracea and oilseed Brassica rapa genotypes in resynthesized rapeseed (Brassica napus) lines
No full textResynthesized (RS) forms of rapeseed (Brassica napus L.; genome AACC, 2n = 38) generated from interspecific hybridization between suitable genotypes of its diploid progenitors Brassica rapa L. (syn. campestris; genome AA, 2n 20) and Brassica oleracea L. (CC, 2n 18) represent a potentially useful resource to introduce resistance against the fungal pathogen Verticillium longisporum into the gene pool of oilseed rape. Numerous cabbage (B. oleracea) accessions are known with resistance to V. longisporum; however, B. oleracea generally has high levels of erucic acid and glucosinolates in the seed, which reduces the suitability of resulting RS rapeseed lines for oilseed rape breeding. In this study resistance against V. longisporum was identified in the cabbage accession Kashirka 202 (B. oleracea convar. capitata), a zero erucic acid mutant, and RS rapeseed lines were generated by crossing the resistant genotype with two spring turnip rape accessions (B. rapa ssp. olerifera) with zero erucic acid. One of the resulting zero erucic acid RS rapeseed lines was found to have a high level of resistance to V. longisporum compared with both parental accessions and with B. napus controls. A number of other zero erucic acid RS lines showed resistance levels comparable to the parental accessions. In the most resistant RS lines the resistance and zero erucic acid traits were combined with variable seed glucosinolate contents. Erucic acid-free RS rapeseed with moderate seed glucosinolate content represents an ideal basic material for introgression of quantitative V. longisporum resistance derived from B. oleracea and B. rapa into elite oilseed rape breeding lines
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
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