1,720,956 research outputs found
Compositional homeostasis of the dinoflagellate Protoceratium reticulatum grown at three different pCO2
No full textIn the CO2-richer world that awaits us, the impact of elevated pCO2 on the allocation of resources in
phytoplankton may have profound repercussions on the physiology of the microalgae and on the
ecology of the ecosystems of which they are part. We studied the overall physiology and cell
composition of the potentially toxic dinoflagellate Protoceratium reticulatum subjected to a mediumterm
increase of CO2.
The physiological responses investigated were growth rates, cell size, photosynthetic and respiratory
rates, and key enzyme activities. Cell composition was assessed by conventional analytical methods and
FTIR spectroscopy.
After 3 generations of incubation at current atmospheric, high and very high pCO2 (380, 1000,
5000ppm CO2), growth, photosynthesis, and dark respiration rates increased significantly, but the
internal composition was only slightly affected.
We propose the homeostasis of cell composition as a strategy that organisms can use to tackle
environmental perturbations, especially when they are of relatively short duratio
Effect of prolonged dark incubation on pigments and photosynthesis of the cave-dwelling cyanobacterium Phormidium autumnale (Oscillatoriales, Cyanobacteria).
No full textThe effect of prolonged darkness on the photosynthetic apparatus of the cyanobacterium Phormidium autumnale was investigated under nonheterotrophic conditions. The purpose of this study was to better understand the processes that allow this organism to rapidly resume growth after prolonged exposure to darkness, as it is often the case in show caves, where periods of darkness are applied to reduce algal proliferation. Phormidium autumnale was subjected to 4 weeks in the dark; this treatment elicited a large decrease in the cells' photosynthetic capacity (Pmax), while the photosynthetic affinity for photons (α) was affected to a smaller degree. Chlorophyll a and carotenoid contents were approximately constant over the 4 weeks of dark incubation, whereas the amount of phycobilins (phycocyanin, allophycocyanin and phycoerythrin) per cell decreased by 50% between the first and the last week of incubation. The relative abundance of the three phycobilins did not vary throughout the treatment, suggesting that the decrease in the number of phycobilisomes was not paralleled by changes in their relative composition. Upon re-exposure to light, cells promptly resumed photosynthesis and were able to cope with high irradiance up to 1600 μmol photons m−2 s−1. The resilience of the photosynthetic apparatus of P. autumnale in the dark may be one of the features that determine the prevalence of this organism in the cave flora at the expenses of more dark-sensitive photolithotrophs (i.e. organisms whose photosynthetic apparatus is substantially reduced or disassembled in the dark)
Homeostasis of cell composition during prolonged darkness.
No full textThe chemical composition of organisms in relation to their
environmental resource availability is an area of intense
research activity. We studied the changes in cell composition
of the cyanobacterium
Phormidium autumnale
in
response to prolonged darkness. Cells allocated their
internal resources in a homeostatic manner, oxidizing all
the three major cellular constituents in a proportional way.
This resulted in constant C/N and carbohydrates, lipids and
proteins ratios that remained unaltered throughout the
whole incubation period. We propose the maintenance of
balanced cell composition (homeostasis) as an evolutionary
strategy related to environmental transitory changes
Ricerche ed attività di monitoraggio ambientale nella Grotta Grande del Vento a Frasassi (Ancona)
No full textl'articolo riferisce sui dati ambientali della Grotat Grande del Vento e riporta i dati delle ricerche biologiche e geologiche condotte. Particolare attenzione è posta alla questione della proliferazione algale (lampen-flora
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
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