1,721,802 research outputs found
Vertical migration mitigates UV effects on zooplankton community composition
No full textSeveral zooplankton species are susceptible to ultraviolet radiation (UV), suggesting that UV may shape zooplankton community composition. Little is known, however, about the quantitative effects of long-term UV exposure in relation to biological processes. Therefore, we studied effects of UV on behaviour, population dynamics and reproduction of several zooplankton taxa. We identified different strategies regarding daytime vertical distribution: a strong response to UV threat, illustrated by Daphnia; a weak, albeit significant response, such as in copepods; and lastly, a stationary position in a depth refuge, as in Chydorus and Eurycercus. The relative abundances of the different zooplankton species were similar and only Daphnia and copepod nauplii displayed a slight decrease in relative abundance in response to UV treatment. Daphnia also reacted to the UV threat by increasing resting egg production, whereas long-term population dynamics for all studied species were surprisingly similar between treatments, despite considerable differences in UV exposure for several months. We conclude that zooplankton communities at temperate latitudes are able to survive increased UV levels due to efficient defences, suggesting that future potential increases in UV radiation may result in only moderate impacts on zooplankton population dynamics and community composition
Vardagen för personer med psykisk funktionsnedsättning : livskvalitet, behov av vård och stöd, socialt nätverk och vardagslivet
No full textLow concentrations, potential ecological consequences: Synthetic estrogens alter life-history and demographic structures of aquatic invertebrates.
No full textContraceptive drugs are nowadays found in aquatic environments around the globe. Particularly, 17α-ethinylestradiol (EE2) may act even at low concentrations, such as those recorded in natural ecosystems. We evaluated the physiological effects of EE2 on cyclopoids and calanoids, common copepods in both marine and freshwater communities. We used three EE2 concentrations and assessed its impact on activity of different physiological endpoints: Acetylcholinesterase (neurotransmission), Glutathione S-transferase (detoxifying system), and Caspase-3 (apoptosis). While EE2 exerts, distinctive effect on detoxifying and apoptotic systems, no effect on AChE was observed at environmental doses. Our results show that EE2 exposure affects differently copepod physiology endpoints, altering moulting process, adult recruitment in calanoids and calanoid to cyclopoid ratio. The ecological consequences of this underlying physiological process may affect since life history to population and community structures, and this represent a new aspects of this xenobiotic in natural systems.Fil: Souza, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Hallgren, Per. Lund University; SueciaFil: Balseiro, Esteban Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Hansson, Lars Anders. Lund University; Sueci
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
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