1,721,040 research outputs found
Impact of cadmium on young plants of Populus euphratica and P. × canescens, two poplar species that differ in stress tolerance
No full textPopulus euphratica is a salt tolerant species, and Populus × canescens is a salt sensitive species. Because stress tolerance is mediated by an array of overlapping defense mechanisms, we hypothesized that P. euphratica would confer co-tolerance to heavy metal stress. To test this hypothesis, both poplar species were exposed to 50 μM Cd for 24 h in hydroponic solutions. For the analyses of stress symptoms in roots and leaves, we used nutrient element concentrations and transcriptional responses of 28 stress- and defense-related genes. The roots showed strong Cd accumulation, but less in P. euphratica than in P. × canescens. In contrast, the leaves of P. euphratica accumulated 10-times more Cd than those of P. × canescens. Cd-stressed leaves of P. euphratica displayed water loss and wilting. Both species revealed contrasting transcriptional responses of defense genes to Cd stress. In P. euphratica, glutathione reductase, dehydroascorbate reductase and glutathione S-transferases of the theta and tau classes showed increases in transcript levels in response to Cd, pointing to oxidative stress and a strong activation of detoxification mechanisms. In contrast, in P. × canescens transcript levels of genes involved in signaling, activation of, and protection from drought stress were significantly increased including glutathione S-transferases of the phi class (early response to dehydration). Our data show that P. euphratica salt tolerance does not confer Cd tolerance and suggest that failure to activate early protection contributed to higher Cd sensitivity in P. euphratica than in P. × canescens
pH influence on root growth and nutrient uptake of Pinus pinaster seedlings
No full textTwo-week old Pinus pinaster seedlings were grown at four pH values ranging from 3.5 to 6.5. Root elongation rate progressively decreased with the duration of treatment at 3.5 and 6.5 pH. After 4 weeks 3.5 pH grown roots showed the lowest length and the highest biomass because of their marked thickening. The pH of the culture solution did not influence lateral root initiation, whereas it affected their length, that was highest at 3.5 pH and lowest at 6.5 pH. Mineral nutrition was affected by the pH of the culture solution. The P, Fe and Al concentration in roots was higher in the 3.5 and 4.5 pH solutions. On the contrary, a lower K, Ca, Mg and especially Mn content of roots was measured in the 3.5 pH grown seedlings. These results suggest that P. pinaster is able to grow on a wide range of acidic soils changing the morphology of the root system in relation to soil 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
JWS online: a web-based tool for curation, review, sotrage and analysis of kinetic models.
No full textDispelling 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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