1,720,967 research outputs found
Effect of iron intake and its relationship with a chelator (EDTA) on the growth and mineral composition of algae (Platimonas suecica) and rotifers (Brachionus plicatilis)
No full textAfin d'etudier l'incorporation des oligoelements dans la chaine trophique, les repercussions des variations de la composition en mineraux traces (Fe, Zn, Cu, Mn) du milieu de culture des algues unicellulaires sont suivies dans une chaine alimentaire artificielle constituee par des algues (Platymonas suecica) et des rotiferes (Brachionus plicatilis). Une forte teneur en chelateur diminue la production des algues et des rotiferes cultives en bloom; elle diminue l'incorporation des mineraux traces dans les algues mais cet effet ne se repercute notablement au 2e maillon de la chaine (chez les rotiferes); que pour l'incorporation du zinc. Une croissance optimale de Platymonas suecica est obtenue avec un milieu contenant 267μg de Fe/l et 4,97 mg/l d'EDTA. Ce milieu donne aussi les meilleures croissances des rotiferes. L'incorporation du fer dans les algues est directement correlee a la dose presente dans le milieu, les autres mineraux (Zn, Cu, Mn) ne sont pas clairement affectes par les differentes concentrations de fer. Par contre la teneur des rotiferes en mineraux est influencee par les doses de fer employees pour la lutte des algues, les fortes concentrations testees augmentent l'incorporation du fer diminuent celle du zinc, du cuivre et du manganese. Les interactions entre le fer et les autres mineraux ne sont pas donc semblables pour les algues et pour les rotiferes.In order to study the incorporation of trace elements into a trophic chain, the effects of the variations in the composition of trace minerals (Fe, Zn, Cu, Mn) of the algal culture medium are followed in an artificial food chain consisting of the unicellular alga Platymonas suecica and the rotifer Branchionus plicatilis cultivated in bloom. A high level of chelating agent decreases the production of algae and rotifers, it depresses the absorption of trace minerals into algae, but this effect is clearly reflected in the 2nd level of the food chain (in rotifers) only as far as zinc is concerned. An optimum growth of P.suecica is obtained when the medium contains 267 kg/l of Fe and 4,97mg/l of EDTA. This medium gives also the best growth of rotifers. In the algae, iron absorption is directly correlated with its concentration in the medium. The absorption of other minerals (Zn, Cu, Mn) is not dependent on iron concentrations. However the trace mineral contents of rotifers are (i.e. at the second step of the food chain) influenced by the iron levels in algal culture: high Fe concentrations increase its absorption and decrease that of zinc, copper and manganese. Therefore the interactions between iron and other minerals are not similar in rotifers and algae.Publishe
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
Study of hydrological parameters in the large of Kerkennah Islands waters.
No full textLes resultats obtenus au terme de cette etude montrent que les eaux orientales au large des iles Kerkennah sont homogenes, du point de vue hydrobiologique, et qu'elles ne sont soumises ni a l'influence d'apports eutrophisants d'origine endogene, ni aux effets nefastes lies a la propagation du phosphogypse, qui continue a enrichir la partie sud du golfe de Gabes en sulfates et phosphates, en particulier. Il en decoule, egalement, que la zone d'etude est l'abri de sources de pollution chronique, de nature a y entrainer des variations importantes des parametres hydrobiologiques. Enfin l'evolution bathymetrique de la chlorophylle a permis de deceler une activite photosynthetique maximale a 10m de profondeur, denotant ainsi la haute transparence de l'eau de la zone prospectee.This study concerning the hydrobiological parameters on the east area of Kerkennah islands, located in the north part of Gabes gulf, gives us the following results: -sea water collected samples are homogeneous in the hydrobiological field. The studied area is not moved by eutrophication and by dissemination of phosphogypsum, which increases, in particular, the sulphate and phosphate amounts in the south part of Gabes gulfs. The concerned sea environment is not subject to chronic pollution sources, which can generate great variations of hydrobiological factors. Finally, the discovery of maximum photosynthesis at at 10 m of depth means a good transparency of analysed sea water.Publishe
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
Study of heavy metals (Cd, Pb, Cu and Hg) ecosystem contamination in Kerkennah Islands.
No full textL'etude des metaux lourds (Cd, Pb, Hg et Cu) dans les sediments et quelques especes des poissons provenant de la zone orientale des iles de Kerkennah durant la periode du 4 au 7 Juin 1994, montre que, cette region presente une situation environnementale normale pour une zone non soumise a une pollution chronique, due a l'abondance des metaux lourds dans le milieu. Les concentrations des metaux dans les sediments et dans le muscle des especes etudiees sont faibles par rapport aux normes limites tolerables par l'Organisation Mondiale de la Sante(OMS).The subject of this work is to estimate the degree of pollution caused by the presence of heavy metals such Cd, Pb, Hg and Cu, in the samples of sediments and fish collected from the eastern side of the islands of Kerkennah, from 4 to 7 of June 1994. The mean results show that this area is not submissive to a chronic pollution caused by an important concentration of heavy metals. The recorded concentration of heavy metals in sediments and fish muscles are widely lower than the norms fixed by the World Health Organization.Publishe
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