1,720,957 research outputs found
Net CO2 exchange of in vitro plum cultures during growth evolution at different photosynthetic photon flux density
No full textCO2 concentration was monitored during three 15-day subculturing cycles in vessels containing actively proliferating plum cultures of Prunus cerasifera, clone Mr.S. 2/5. The effects of two photosynthetic photon flux density regimes: 50 ± 5 μmol m-2 s-1 and 210 ± 5 μmol m-2 s-1 were compared. Three distinct phases in the CO2 trend were distinguished during each culturing cycle of both light treatments. In the first, occurring at the beginning of the culture cycle, the amount of CO2 emitted by the cultures during dark periods was greater than that assimilated during the light periods. In the second phase, the opposite trend was detected, while in the third, the range of CO2 day-night fluctuations increased or remained stable according to the number of explants per vessel. The treatment with 210 ± 5 μmol m-2 s-1 did not modify the CO2 phase trend but induced more pronounced fluctuations in day-night CO2 concentration. Under this light treatment, cultures reached CO2 compensation point for a period as long as 48% of the total number of light hours, while under 50 ± 5 μmol m-2 s-1, it was only 8%. The different range in CO2 day-night fluctuations monitored throughout a subculturing cycle, appeared to be mainly induced by changes in culture growth dynamics
CO2 dynamics and growth in photoautotrophic and photomixotrhopich apple cultures
No full texthe daily dynamics of CO2 concentration in the culture vessels and the photoautotrophic or photomixotrophic growth capacity of apple (Malus pumila hybrid MM 106 paradisiaca x Northern Spy) cultures were studied. The photoautotrophic cultures were grown on a sugar-free growth medium and submitted (0S+CO2) or not (0S-CO2) to periodic injections of exogenous CO2. The photomixotrophic cultures were grown in the presence of 30 g dm-3 sucrose, with (30S+CO2) or without (30S-CO2) CO2 enrichment. The photosynthetic photon flux density applied was of 210 ± 5 μmol m-2s-1. In the 0S-CO2 treatment, CO2 showed rather uniform and narrow light-dark fluctuations throughout the culturing cycle. In the 30S-CO2 treatment, the daily ratio between CO2 produced during the dark period and that uptaken during the following light period, was almost always above 1 with the only exception of a few days (from the 5 th to the 9th day) when the amount of photosynthesised CO2 was equal to or higher than that produced during dark respiration. The 0S+CO2 cultures needed to be enriched all days with exogenous CO2 to avoid periods of gas deficiency while in 30S+CO 2 the CO2 injected the first culturing day was uptaken over 5 d, thereafter, daily injections were necessary. Culture fresh and dry mass, number of newly formed shoots and number of nodes per shoot in 0S+CO 2 treatment did not statistically differ from the values obtained with 30S-CO2. The highest growth was observed in 30S+CO2 treatment. The increase in culture fresh mass due to 1 μmol of CO 2 added to the culture vessels was 1.54 and 1.36 mg for 30S and 0S respectively, while in terms of dry mass the increase was about 2.5 times higher in the sugar-enriched treatment. CO2 enrichment accounted for 77.3 % and 21.2 % of the final fresh mass in 0S+CO2 and 30S+CO 2, respectively
A new diploid species of Leucanthemum (Asteraceae, Anthemideae) from Liguria (northwestern Italy)
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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
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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