1,720,998 research outputs found
Heavy metals influence mineral nutrition of tree seedlings
No full textThe influence of Cd and Cu on growth, chlorophyll content and mineral nutrition of Pinus pinea L., Pinus pinaster Ait. and Fraxinus angustifolia Vahl. was investigated. Two-week old seedlings were grown for 4 weeks in a complete culture solution and range of metals were added as CuSO4 (0.012-5 μM) and CdSO4 (0.0-5 μM). The biomass of the Pinus species was significantly lower than that of controls only at the supply of 5 μM Cu, whereas in F. angustifolia both shoot and root biomass decreased in heavy metal treatments. Chlorophyll content decreased in all species with increasing Cd or Cu supply. Cd-treated leaves of F. angustifolia were chlorotic. The Mn and Zn content of roots decreased in all species at increasing Cu and Cd concentrations, whereas the Ca and Mg uptake and distribution differed among species
Metal pollution and forest decline
No full textThe chapter illustrates the primary sources of heavy metal pollution in forest ecosystems and discusses its influence on health and natural regenertaion of forest ecosystems. Strategies for the amelioration of heavy metal stress are also presented
The influence of pH on root morphology and mineral content of Pinus pinaster Ait. seedlings
No full textTwo-week old seedlings of Pinus pinaster Ait. were grown in nutrient solutions at pH values ranging from 3.5 to 6.5. Acidity exerted a different influence on the growth of the main and lateral roots, thus changing the morphology of the whole root system. Roots grown at 3.5 pH had the shortest length, but the highest biomass and were markedly thickened. The total number of 2nd order lateral roots per plant was not significantly influenced by pH, whereas their length and the development of 3rd roots were the highest at 3.5 pH and the lowest at 6.5 pH. Mineral nutrition was affected by the pH of the culture solution. The P and Fe concentrations in roots were higher in the 3.5 and 4.5 pH solutions than in 5.5 and 6.5 pH. In contrast, lower K, Ca, Mg and especially Mn contents were found in the roots grown at 3.5 pH. However, needle dry weight was unaffected by low pH and neither chlorosis nor critical levels of mineral elements were observed. These results suggest that the compensatory growth of lateral roots allows P. pinaster seedlings to mantain an adequate nutritional status in the shoot even at highly acidic conditions
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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