1,720,975 research outputs found
Variabilità morfologica e molecolare in un popolamento misto di Quercus suber L. e Quercus cerris L.
No full textMonitoring of air pollutants in Florence (Italy) with erbaceous and woody bioindicators
No full textAn integrated biomonitoring activity was carried out during 1996 in Florence. Ten fully equipped stands of bioindicators were set up in the city; observations were performed between May and October 1996. Ozone was monitored with the sensitive cultivar Nicotiana tabacum Bel W3, by means of the usual Leaf Injury Index (LII). The unsensitive cultivar Nicotiana tabacum Bel B was used as a control. Heavy metals (Pb, Cd, Cr, Cu, Fe, Ni), chlorine and sulphur were detected with the bioaccumulator Lolium multiflorum L., harvesting and analyzing micro-cultivations of this species once a month. Further, some potted plants of Pinus halepensis Mill, were placed in five of these stands in order to test their sensitivity to ozone and verify their possible use as bioindicators. Results show that the LII of the sensitive tobacco cultivar increases as one moves from the centre towards the peripheral and suburban areas of Florence; this finding correlates perfectly with the air ozone concentrations measured using traditional automatic methods. Heavy metals, on the contrary, show an opposite trend, with concentrations decreasing as one moves from the centre to the suburbs. No trends were detected for chlorine and sulphur. As far as Pinus halepensis is concerned the characteristic chlorotic mottles, described in the literature as ozone-like symptoms, were observed on the needles. These symptoms were detected in areas with high ozone concentration, but not in the control stand. Despite its sensitivity to ozone, the use of Pinus halepensis as a biomonitor appears doubtful because no proportionality was observed between injury and ozone concentration
Anatomical and ultrastructural alterations in Pinus pinea L. needles treted with simulated sea aerosols
No full textThe effects of sea pollution by surfactants on coastal vegetation have been studied for several decades now in a number of European and non European regions. The damage is normally attributed to an excessive absorption of salts as a result of the action of the surfactants which lower the surface tension of the droplets of aerosol and make it easier for them to penetrate the stomata. Yet researchers have also discussed the possibility that surfactants may have a direct phytotoxic effect. This paper illustrates an anatomical and ultrastructural study of Pinus pinea L. needles treated with simulated sea aerosol for brief exposure periods. The results of this study confirm that anionic and non-ionic surfactants are directly toxic and affect mainly the stomatal apparatus, including both the epistomatal network and the guard cells and substomatal cells
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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