1,720,968 research outputs found
Cocconeis intermedia Héribaud & Peragallo: nouvelles informations sur la morphologie et l’écologie d’une espèce de diatomée peu connue
No full textL’espèce Cocconeis intermedia a été décrite et illustrée en 1893 par Héribaud & Peragallo. Elle a été trouvée comme diatomée fossile dans des échantillons prélevés dans des dépôts situés à Randanne, Ponteix et Verneuge en Auvergne (département du Puy de Dôme, Massif central, France). La forme minor de l’espèce, également décrite par Héribaud & Peragallo dans la même région (dépôts à Randanne), ne diffère selon les auteurs que par sa taille plus petite. Cocconeis intermedia a ensuite été mentionnée comme étant une variété de Cocconeis placentula (Cocconeis placentula var. intermedia Héribaud & Peragallo) dans certains livres floristiques classiques et ce taxon a été rarement cité dans la littérature. Certaines études ont signalé sa présence dans les diatomites du district de Terrebonne en Oregon (USA) et, plus récemment, comme forme vivante dans les eaux peu profondes des écosystèmes de la mer Noire et de la mer d'Azov et dans les sources thermales et minérales du Pamir en Tadjikistan. À ce jour, les détails morphologiques et les préférences écologiques de cette espèce n’ont pas été documentés. Cocconeis intermedia a été récemment observée dans une petite source thermo-minérale appartenant aux eaux thermales de San Saturnino (Sardaigne, Italie), connues depuis l’époque romaine sous le nom de Aquae Laesitanae. Elle était présente dans six échantillons prélevés sur différents substrats en été 2016 et en hiver 2017 et elle était surtout abondante dans l’épiphyton en été (abondance relative = 13,3%) et dans l’épilithon en hiver (abondance relative = 10,6%). Nous présentons des détails morphologiques supplémentaires de l’espèce avec des images en microscopie optique et en microscopie électronique à balayage et de nouvelles informations sur son écologie et sa distribution spatiale et saisonnière en Sardaigne
Composition, structure, and distribution of diatom assemblages in Mediterranean thermal spring ecotones affected by natural and human disturbances
No full textSprings are unique aquatic environments that significantly contribute to regional and global biodiversity but are also susceptible to disturbances because of their small size. Mediterranean thermal springs remain poorly studied, and little is known about how different environmental and disturbance factors affect their aquatic communities. In this study, we analyzed diatom assemblages from six thermal springs of Sardinia (Italy), both isolated and connected to river systems, their relationship with environmental variables, ecotonal properties (i.e., transition of springs with terrestrial and/or river environments) and primary sources of disturbance. A total of 196 species (65 genera) were found from two substrates (cobbles and surface sediments). Overall, low discharge and ecotonal properties, influenced by natural and human disturbances (temporary flooding, water abstraction and recreational activities), contribute to form heterogeneous diatom assemblages composed of aquatic-aerial, aerial and planktonic species. Springs connected to rivers and that are more disturbed showed a higher presence of planktonic and habitat generalist species and a higher species richness, diversity and evenness than more isolated springs. By contrast, the latter seems to harbor smaller pools of taxa with crenophilous species and species with a preference for less disturbed habitats or with more restricted geographical distribution. Water temperature, “river influence,” discharge, orthophosphates and dissolved inorganic nitrogen played a major role in shaping diatom assemblages. Our results indicate that diatoms can provide helpful information about the ecological functioning of thermal springs and can be an effective tool to track their environmental changes related to the increasing natural and human pressures in the Mediterranean area
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
Epiphytic and epilithic diatom assemblages in Mediterranean karst springs: a case study from Sardinia (Italy)
No full textCocconeis intermedia peragallo & héribaud (Bacillariophyta): New information on morphology, distribution and ecology of a poorly known diatom species
No full textCocconeis intermedia was originally described by Peragallo & Héribaud in Héribaud (1893) as a fossil diatom species from samples collected in the Puy-de-Dôme department, Auvergne-Rhône-Alpes region (France). After the first brief description, the species was mostly mentioned as C. placentula var. intermedia in classic floristic books and, over time, it was reported living in a wide variety of aquatic environments. Despite this, the morphological features of C. intermedia remained poorly known: detailed information and micrographs are not available in the literature and the fine structure was never investigated. A Cocconeis species found in the thermomineral spring San Saturnino in Sardinia (Italy) was identified as Cocconeis intermedia Peragallo & Héribaud after an extensive literature search and a comparison with specimens from slides of Tempère & Peragallo collection housed in the Natural History Museum (London, United Kingdom). In this study we provide an amended description of the species with new morphological details as observed in light and scanning electron microscopy. We also provide additional information on the seasonal distribution and occurrence of the species on a variety of substrata in its habitat in Sardinia
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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