1,720,981 research outputs found
Chemical Composition and Antioxidant Activity of Essential Oils in Origanum vulgare subsp. gracile at different Phenological Stages and Plant Parts
No full textOriganum vulgare, a popular flavoring herb, is valued for several biological properties. The present study focused on the chemical composition and antioxidant activity of the essential oils of Origanum vulgare subsp. gracile in different plant parts and at different phenological stages. Qualitative and quantitative analyses of the essential oil identified 41 constituents that varied with plant age and organ. The phenolic monoterpenoid carvacrol (18.1–79.2%) was predominant in all the essential oil samples. Other major constituents were p-cymene (3.9–18.0%), γ-terpinene (0.9–15.8%), carvacrol methyl ether (0.8–9.9%), and (Z)-α-bisabolene (0.5–8.7%). Among the different plant parts and phenological growth stages, the highest levels of carvacrol were identified in the essential oils from flowers (79.2%), roots (70%), and the early vegetative growth (67.34%). All the essential oils exhibited high radical-scavenging properties as shown in the DPPH* assay. The essential oils from flowers, however, exhibited the highest antioxidant activity and could be used as a preservative agent on an industrial scale
Chemical Characterization of the Essential Oil Compositions from Iranian Populations of Hypericum perforatum L.
No full textHypericum perforatum L. (St. Johns’ wort) is the most commercially important species of the genusHypericum and contains a wide range of components including naphthodianthrones, phloroglucinols,tannins, xanthones, phenolic acids and essential oil. In the present study, for the first time the varia-tion of the essential oil compositions among 10 wild populations of H. perforatum growing in Iran wasassessed. According to the GC-FID and GC–MS analyses, a total of forty-six components were identifiedin 10 H. perforatum populations with relatively high variation in their composition. Among chemicals,2,6-dimethyl-heptane (6.25–36.07%), ̨-pinene (5.56–26.03%), ı-cadinene (0.0–22.58%) and -cadinene(0.0–16.9%) were found as the most abundant compounds in their essential oils. The higher amounts ofthis components were identified in the oil of Azadshahr, Kharw, Nor and Mashhad populations, respec-tively. Cluster analysis grouped the studied populations into four different chemotypes: chemotype I(ı-cadinene/ ̨-humulene), chemotype II ( ̨-pinene), chemotype III (-cadinene) and chemotype IV (2,6-dimethyl-heptane/ ̨-pinene). In fact, local abiotic factors such as moisture, temperature, topography,edaphic and/or biotic selective factors (associated fauna and flora) act on loci of the terpene-biosynthesispathways and contribute to the emergence of different chemical oil profiles. Intraspecific variation in thechemical profile of the Iranian populations provided possibility of selection of those with specific aromasor chemical profiles accompanied with biological document, being of interest at industrial level. Obtainedresults provided new insight for Iranian H. perforatum germplasm to be used in breeding programs anddevelopment of effective conservation strategies
Sumac (Rhus coriaria L.) fruit: essential oil variability in Iranian populations
No full textSumac (Rhus coriaria L.), recognized in Iran and other areas of the Middle East as a very popular flavoring spice, contains a wide range of medicinally active components including organic acids, phenolic acids, flavonoids, anthocyanins, hydrolyzable tannins and terpenoids. In the present study, for the first time the variation of the essential oil compositions in R. coriaria fruits, collected from fourteen different locations in Iran, was assessed. A significant variability in the essential oil content was observed among the investigated populations (ranging from 0.04 to 0.19% (v/w)). GC-FID and GC–MS analyses of the essential oils identified a total of fifty-seven components. (E)-Caryophyllene (5.9–50.3%), n-nonanal (1.8–23.3%), cembrene (1.9–21.7%), α-pinene (0.0–19.7%), (2E,4E)-decadienal (2.4–16.5%) and nonanoic acid (0.0–15.8%) were identified as the main constituents of the essential oils, depending on the populations. The highest amounts of the mentioned components were identified in the essential oil of Tovrivar, Torbat jam, Qom, Kashmar, Torbat jam and Yazd populations, respectively. According to principal component (PCA) and cluster analyses (CA) the studied populations grouped into five different chemotypes: i.e., chemotype I ((E)-caryophyllene), chemotype II ((E)-caryophyllene/α-pinene), chemotype III ((E)-caryophyllene/cembrene), chemotype IV (nonanoic acid/cembrene), chemotype V (n-nonanal/(2E,4E)-decadienal). Such variability in essential oil compositions of Iranian sumac provides possibility to select populations with specific aroma profiles for domestication, breeding and industrial applications and suggests the effective in situ and ex situ conservation strategies for all populations and chemotypes of R. coriaria
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
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