1,721,009 research outputs found
Isolation of European pear S-haplotypes using S-homozygotes derived from bud-selfing
No full textGametophytic self-incompatibility is a mechanism that prevents self-fertilization through a specific pollen-pistil recognition, genetically controlled by the single S locus. In the Pyrinae the S locus has a quite complex structure including a single female (pistil-expressed) gene, the S-RNase, and a number of male (pollen-expressed) F-box genes that act coordinately in a non-self-recognition system. While each Shaplotype segregates as a single unit, gene duplication and genetic exchange seem to play an essential role in the evolution of pollen S-specificities; as a result, extant Shaplotypes differ for the number, position and arrangement of F-box genes. So far, the genomic characterization of some S-haplotypes has been achieved using genomic libraries; the use of S-homozygotes can be an alternative source of information to characterize the pool of F-box genes belonging to a single haplotype. To overcome the self-incompatibility barrier, selfing can be forced by manually pollinating pistils of immature flowers ("bud-selfing"): As the concentration of S-RNases in the early stages of the pistil development is not yet fully effective, a portion of self-pollen tubes can escape the inhibition. The progeny obtained show a mendelian (1:2:1) segregation for the two parent S haplotypes, allowing the isolation of S-homozygotes in half the seedlings; since a low vigor is expected as a consequence of the increase in homozygosity, these genotypes are maintained and multiplied in vitro. This material will be useful for the identification and characterization of F-box genes in different Shaplotypes, as a first step for investigating their roles in the determination of S specificities as well as their evolutionary dynamics
Mela Rosa Romana: valorizzazione e recupero del germoplasma frutticolo dell’Appenino Tosco-Emiliano
No full text
Shoot organogenesis from apricot meristematic bulks
No full textRegeneration from apricot mature tissues, previously attempted as a tool to transform susceptible cultivars with PPV resistance genes, turned out to be a very challenging goal. An alternative approach, called 'meristematic bulk' that was reported to be successfully applied to the genetic transformation of peach and other fruit species, was attempted. In this approach shoot organogenesis was achieved by obtaining, through cytokinin treatments, a highly morphogenic stem tissue from the proximal part of micropropagated shoots. Three apricot cultivars ('Boreale', 'San Castrese', and 'Vitillo'), known as recalcitrant to tissue culture, are being tested for regeneration using this method. In addition to cytokinins, other phytoregulators, as well as ethylene inhibitors, seem to play an important role first in the production of meristematic bulks, then in the adventitious shoot formation subsequent to bulk cutting. In view of the possible recovery of transgenic shoots from future transformation experiments, methods are pursued promoting a short proliferation callus phase and a delayed shoot differentiation, instead of the prompt development of preformed buds. Very promising results have been obtained from all the cultured genotypes
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
Agricoltura resiliente: innovazioni nella gestione dei sistemi frutticoli per mitigare i cambiamenti climatici
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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