1,720,972 research outputs found
Effect of cultivar on minor components in Tunisia olive fruits cultivated in microclimate
No full textThis paper evaluates the usefulness of three chemical parameters (composition of volatiles compounds, total phenols and fatty acids) as a tool to discriminate the olive oils obtained from three varieties (Oueslati, Chemlali and Chetoui). These varieties are included among the cultivars permitted by the disciplinary for the production of the ‘‘Kairouan olive oil’’, a Tunisian protected designation of origin (PDO) product. The olives were collected during the year crop 2009/2010 from the same orchard (calcareous soil), in order to eliminate geographical and climatic influences. Analysis of the effect of cultivar on the different analytical values, revealed statistically significant differences in some parameters, mainly in free fatty acid and phenol contents and oxidative stability. Furthermore, most of the quality indices and fatty acid composition showed significant variations among olive varieties. Oueslati variety had the highest values of oleic acid, whereas Chetoui was noteworthy for its high content of phenolic compounds. The major volatile component was the C6 aldehyde fraction whose content varied greatly between the different varieties: the (E)-2-hexenal content ranged from 20.9% in the oil obtained from the Oueslati variety to 7.7% in the case of Chemlali one; the amount of hexanal ranged from 10.2% in Oueslati to 3.7% in Chetoui. These results suggest that the genetic factor (cultivar) influences the volatiles formation
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
Chemical composition of virgin olive oils from the Chemlali cultivar with regard to the method of the olive tree propagation
Full text linkThis paper reports for the first time a discrimination study based on the antioxidant compounds, oxidative stability and volatile compounds of virgin olive oil samples obtained from fruits of the main Tunisian olive cultivar (Chemlali) using two methods of olive tree propagation (suckers and cuttings). There were significant differences between the oils from the two methods. Olive oil samples obtained from the fruits of trees from suckers had a higher content of oleic acid (63.8%), higher contents of chlorophyll and carotenoids (3.01 mg/kg and 1.9 mg/kg respectively), a higher content of (E)-2 hexenal (66.1%) and a higher content in total phenols (890 mg/kg).
Interestingly, more stable oil was obtained from the olives from suckers compared to the olives from cuttings. These results can be used to discriminate and to characterize the Chemlali olive oils from each origin of olive tre
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
Influence of olive storage period on volatile compounds and oil quality of two Tunisian cultivars of Olea europaea, Chemlali and Chetoui
No full textOlives (Olea europaea cv. Chemlali and Chetoui) used for oil production were stored, in plastic containers, at 5°C for four different periods (0–3 weeks) before oil extraction. After storage, the oils were extracted from the fruits, and the acidity, peroxide value, coefficients of specific extinction at 232 and 270 nm, stability, pigments, total phenols, fatty acids, and volatile compounds were determined. The results showed that storage of fruits produced losses in the olive oil quality. During storage, a marked decrease in total phenols content was observed. The cultivar richer in phenols (862.16 mg kg)1 in Che ́toui) had a lower loss (25%). On the contrary, in Chemlali olive oil, the starting value of 728.52 mg kg)1 decreased to 469.25 mg kg)1, with a loss of 35%. Che ́toui and Chemlali olive oils presented the highest oxidative stability before storage (58.76 and 47.05 h, respectively), while the lowest values were recorded using olives stored for 3 weeks (54.46 and 43.43 h, respectively). The changes in the volatile bouquet were determined using headspace solid phase microextraction (HS-SPME). Thirty compounds were characterised by GC–FID and GC–MS. Compounds belonging mainly to alcohols, esters, aldehydes, ketones and hydrocarbons chemical classes characterised the volatile profile
EFFECTS OF THE HALOPHYTES TECTICORNIA INDICA AND SUAEDA FRUTICOSA ON SOIL ENZYME ACTIVITIES IN A MEDITERRANEAN SABKHA
No full textSterolic composition and triacylglycerols of Oueslati virgin olive oil: comparison among different geographic areas
No full textThe main triglycerides (TG) identified in the Oueslati virgin olive oil were 1,2,3-trioleylglycerol (OOO), 2,3- dioleyl-1-palmitoylglycerol (POO) and 2,3-dioleyl-1-linoleylglycerol (LOO) representing more than 80% of the total area of peaks in the chromatogram. Other minor triacylglycerols were 2,3-dioleyl-1-stearoylglycerol (SOO), 2-oleyl-3-palmitoyl-1-stearoylglycerol (SOP), 1-linolenoyl-2-oleyl-3-palmitoylglycerol (LnOP), 1,2-dilinoleyl-3-palmitoylglycerol (LLP), 1, 3-dioleyl-2-linolenoylglycerol (OLnO), 1-linolenoyl-2-linoleyl-3-oleylglycerol (LnLO) and 1,2,3-trilinoleylglycerol (LLL). The sterol profile of Tunisian virgin olive oils produced from Oueslati cultivar was established by gas chromatography using a flame ionisation detector (GC-MS). More than 10 compounds were identified and characterised. As expected for virgin olive oil, the main sterols found in all Oueslati olive oils were b-sitosterol, D5-avenasterol, campesterol and stigmasterol. Cholesterol, 24-methylenecholesterol, clerosterol, campestanol, sitostanol, D7-stigmastenol, D5, 24-stigmastadienol and D7-avenasterol were also found in all samples, but in lower amounts. Most of these compounds are significantly affected by the geographical origin of the oil. Besides the sterol components, two triterpene dialcohols, erythrodiol and uvaol, were also detected
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
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