1,720,982 research outputs found
Determination of As concentration in earthworm coelomic fluid extracts by total-reflection X-ray fluorescence spectrometry
No full textEarthworms are often used as sentinel organisms to study As bioavailability in polluted soils. Arsenic in earthworms is mainly sequestrated in the coelomic fluids whose As content can therefore be used to asses As bioavalability. In this work, a method for determining As concentration in coelomic fluid extracts using total-reflection X-ray fluorescence spectrometry (TXRF) is presented. For this purpose coelomic fluid extracts from earthworms living in three polluted soils and one non-polluted (control) soil have been collected and analysed. A very simple sample preparation was implemented, consisting of a dilution of the extracts with polyvinyl alcohol (PVA) using a 1:8 ratio and dropwise deposition of the sample on the reflector. A detection limit of 0.2 μg/l and quantification limit of 0.6 μg/l was obtained in the diluted samples, corresponding to 2 μg/l and 6 μg/l in the coelomic fluid extracts, respectively. This allowed to quantify As concentration in coelomic fluids extracted from earthworms living in soils polluted with As at concentrations higher than 20 mg/kg (considered as a pollution threshold for agricultural soils). The TXRF method has been validated by comparison with As concentrations in standards and by analysing the same samples by ICP-MS, after acid digestion of the sample. The low limit of detection, the proven reliability of the method and the little sample preparation make TXRF a suitable, cost-efficient and “green” technique for the analysis of As in earthworm coelomic fluid extracts for bioavailability studies
Effects of chromium yeast supplementation on growth performances and meat quality in rabbits
No full textThe aim of the trial was to estimate the effect of dietary Cr-yeast addition to growing rabbit diet on growth performance, meat composition, muscle fatty acid profile and Cr content of meat and edible organs. Ninety-six male rabbits were weaned at 35 days and divided into 4 groups (T1, T2, T3 and T4) of 24 each. The animals were fed ad libitum for the whole trial (44 days) with pelletted diets differing in the presence of yeast (Saccharomyces cerevisiae), grown or not on Cr-enriched medium. The control diet (T1) did not contain yeast, the T2 diet was supplemented with non-enriched yeast, while the T3 and T4 diets were supplemented with Cr(III)-enriched yeast to increase the concentration of Cr by 0.400 mg/kg and 0.800 mg/kg, respectively. Control diet (T1) contained 0.830 mg/kg Cr due to the presence of the trace element in raw materials. The dietary treatment did not affect either the mortality, or the growing and slaughtering performance, or the incidence of kidneys, scapular and perirenal fat on carcass weight. A reduction in the liver incidence on the carcass was observed in the T3 group compared to the T4 (4.36% vs 5.67%; P<0.01). Hind leg proportion on carcass weight and its muscle to bone ratio, as well as chemical, physical and organoleptic characteristics of meat did not differ among groups. The presence of Cr(III) in the feed did not alter the fatty acid profile of muscular fat or the chemical composition, pH and colour of the meat. The Cr concentration in meat and edible organs (liver and kidneys) was not affected by treatment. In conclusion, Cr-yeast supplementation had no positive effects on the rabbit growth performance and carcass and meat quality and did not increase the Cr(III) content of meat for human consumption.[...
Provenance discrimination of Sorrento lemon with Protected Geographical indication (PGI) by multi-elemental fingerprinting
No full textMultielement analysis and chemometric methods were proposed to discriminate the Sorrento lemon (PGI) juices according to geographical origin. In 2018 and 2019, 169 fruits from three farms in PGI area and two in not-PGI area were collected and analysed for essential and not-essential elements by ICP-MS. The PCA of multielement fingerprinting grouped lemon juices from PGI farms revealing a strong differentiation at small geographical scale. The S-LDA discriminated lemon juices for Mo, Ba, Rb, Mg, Co, Ca, Fe, Sr on the two production years, giving 97.7% correct classification, 98.5% accuracy and 93.8% external validation. The good correlation lemon juice vs cultivation soil and the soil discrimination by not-essential elements suggested the use of these elements as reliable indicators of lemon juice provenances. Despite lowering the number of variables, constituted by not-essential elements Ba, Rb, Ti, Co, the use of S-QDA discriminated the lemons juices with 87.5% accuracy and 83.9% validation
Determination of rare earth elements in tomato plants by inductively coupled plasma mass spectrometry techniques.
No full textGoing 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
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