1,720,998 research outputs found
Quality control of Utermöhl based phytoplankton biovolume estimates: an easy task or a Gordian knot?
No full textQuality control of Utermöhl-based phytoplankton counting and biovolume estimates: an easy task or a Gordian knot?
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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
Calcification types of Oocardium stratum Nägeli and microhabitat conditions in springs of the Alps
No full textHabitat conditions and spring-associated limestones (SALs) formed by ambient precipitation with the biotic contribution of the desmid Oocardium stratum Nägeli 1843 (Zygnematophyceae) were studied in 5 springs along a north-south transect across the central Eastern European Alps. Spring waters were characterized by permanent flow and temporally almost stable physicochemical conditions, but variable relationships among major ions (especially HCO3-:SO42- and Ca2+:Mg 2+) among sites. In most cases, CO2 supersaturation (0.2-1.8 μM/L) caused in situ depression of pH from near equilibrium (8.3) to <8, with a minimum pH of 7.1. SAL areas dominated by Oocardium growth were greatest some distance downstream of the spring origin where degassing of excess CO2 had occurred and pH had risen to >8.1. The calcified segments of spring streams were limited to areas <300 m from the spring mouth. Within the uppermost segment of larger rheocrenes (CO2 supersaturated areas), extensive weakly calcified bryophyte crops (Eucladium verticillatum, Palustriella commutata) were replaced further downstream by Oocardium-spiked calcified coatings. The various morphologies of Oocardium cells (assessed with light microscopy [LM], scanning electron microscopy [SEM], and petrographic thin sections) revealed different types of calcification, from micritic (<1-4 μm) to sparitic calcites (>100-1000 μm) whose ultrastructural features were best seen with SEM. The distribution of SAL types within and among sites was evaluated in relation to water-chemistry and additional environmental variables. The findings were compared with earlier records from the Alps and other mountain areas of Europe (in particular, Croatia and UK) to facilitate recognition and delimitation of Oocardium niches in the environment and to foster protection of these rare habitats. © 2012 The Society for Freshwater Science
Long-term trends in species composition and diurnal migration of dinoflagellates in Lake Tovel (Trentino, Italy)
No full textEco- fingerprinting of Borghiella dodgei (Dinoflagellata): experimental evidence of a narrow environmental niche
Full text linkThe dinoflagellate Borghiella dodgei Moestrup, Hansen et Daugbjerg, was cultivated in the laboratory under different temperature, nutrients, and light conditions. Growth rates, cell biovolume, cyst formation, pigment content, and MAAs were determined. Experiments showed that this algae grew well at low temperatures, and grew slowly without organic supplements. While it was not able to grow in the dark, Borghiella survived for long periods without a light source.
In particular, Borghiella grew well at temperatures of <6 °C. Cell yields increased ten fold with organic supplements and increasing irradiance levels had a positive effect on growth.
Cell volume was not affected by light conditions but increased with an increase in temperature or a lack of nutrients. The formation of thick-walled resting cysts was enhanced by an increase in temperature while light conditions did not effect encystment. Chlorophyll a content per cell was inversely related to irradiance levels. Cultures with a high number of resting cysts were characterized by a red-brick colour and altered peridinin/chlorophyll contents. Even after several years of culturing, Borghiella was still capable of MAA synthesis.
The temporal spatial occurrence of this species in Lake Tovel was confronted with results from in vitro experiments. Borghiella’s growth requirements make it well suited to the unique habitat of Lake Tovel
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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