1,720,976 research outputs found
Diversity of epiphytic diatom flora on Mediterranean seagrasses: morphological aspects and ecological role
No full textDIVERSITY OF EPIPHYTIC DIATOM FLORA ON MEDITERRANEAN SEAGRASSES: MORPHOLOGICAL ASPECTS AND ECOLOGICAL ROLE
M. DE STEFANO (1,2), D.Marino (2), L. Mazzella (1)
Stazione Zoologica di Napoli.
(1) Laboratorio di Ecologia del Benthos, 80077 Ischia (NA),
(2) Laboratorio di Botanica Marina, Villa Comunale, 80100 Napoli
The aim of the present work was to characterize the epiphytic diatom flora on seagrass leaves and to assess their role in such important ecosystems.
Of the different mediterranean seagrasses, such as Posidonia oceanica, Cymodocea nodosa and Zostera noltii, highest diatom species richness and diversity was recorded on P. oceanica, due to the greater surface area for colonization and the complexity of microhabitats. The most frequently encountered diatoms were the genera Cocconeis, Gomphonemopsis, Fragilaria,. Mastogloia and Navicula, belonging to different “growth forms”. In Cymodocea and Zostera the diatom flora was meanly characterized by the Cocconeis group.
Diatom abundances reached densities as high as 3000 cells/mm2 in Posidonia and 8000 in Cymodocea; in Zostera diatoms were at times the only recorded flora with concentrations up to 2500 cells/mm2. The biomass of the Cocconeis group, dominant in all seagrasses, was highest in P. oceanica (1,3 mgC/sh-1), due to the large leaf canopy.
Due to its diversity and abundance, the epiphytic diatom flora largely contribute to the production of the seegrass systems and to the grazing activity of mesoherbivores living in the meadows
Ultrastruttura di tre diatomee appartenenti al genere Cocconeis Ehr. epifite di Posidonia Oceanica (L.) Delile
No full textLe specie del genere Cocconeis Ehr. rappresentano la componente maggioritaria della comunità epifitica a diatomee presente sulle fanerogame marine.
Tale componente, che presenta una variabilità specifica piuttosto bassa, risulta costituita da un film di cellule fittamente appressate e distribuite su buona parte della superfice fogliare (Mazzella et al. 1995). Nell’ambito di uno studio sulla distribuzione e successione della comunità epifita su Posidonia oceanica (L.) Delile presente nelle acque dell’isola di Ischia, abbiamo condotto delle osservazioni sull’ultrastruttura di alcune specie. Le specie studiate, C. britannica Näegeli in Kützing, C. maxima (Grunow) Peragallo et Peragallo, C. pseudomarginata Gregory , pur essendo costantemente presenti non dominano la comunità, presentano dimensioni relativamente grandi, habitus solitario e, frequentemente, sono epibionti sulle altre specie congeneri più piccole che costituiscono la gran parte del film epifita.
L’analisi ultrastrutturale, condotta con l’ausilio del microscopio elettronico a scansione e a trasmissione, ci ha mostrato una morfologia delle valve per molti dettagli contrastante con le descrizioni al microscopio ottico, le uniche finora disponibili per queste specie. Ciò è in parte dovuto alla non risolvibilità a basso ingrandimento di alcuni di questi dettagli ma anche alla sovrapposizione in luce trasmessa di elementi strutturali presenti esclusivamente o nella faccia esterna o in quella interna delle valve.
É stato possibile, inoltre, interpretare in un ottica morfo-funzionale alcuni degli elementi strutturali osservati. In particolare il sistema di aggancio delle due valve presente in due delle tre diatomee osservate, che risulta mediato dal preciso incastro di elementi diversi ma visibilmente complementari presenti sulle due valvocopulae.
L. Mazzella, M.C. Buia and L. Spinoccia 1995: Biodiversity of epiphytic diatom community on leaves of Posidonia oceanica. - In: D. Marino & M. Montresor (Eds.) Proceedings of the 13th International Diatom Symposium. Biopress; Bristol. 241-25
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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