1,720,957 research outputs found
The hilar region in Leucaena leucocephala Lam. (De Wit) seed: structure, histochemistry and the role of the lens in germination.
No full textStructural and histochemical changes in hypocotyl cortex of Prosopis species caused by salinity.
No full textSeed Coat Structure and Histochemistry of Abelmoschus esculentus. Chalazal Region and Water Entry
No full textThe seed coat structure and histochemistry of Abelmoschus esculentus were studied by bright-field, fluorescence and scanning electron microscopy. The seed coat was typical of species of the Malvaceae. The endotesta cells had inner tangential walls which were very thick and autofluorescent. The occurrence of phenolic substances at this level has been related to seed coat imposed dormancy. The palisade cells were composed of three differently shaped parts: an upper ‘prismatic part’, a medium ‘transition part’ and a lower ‘twisted part’. The former was rich in hydrophilic substances, the latter was lignified. The swelling of the ‘prismatic parts’ was related to seed coat cracks. The region controlling onset of water entry was thought to be the chalazal area. Thanks to the presence of a large amount of highly acidic polysaccharide, water was able to penetrate from the permeable maternal tissue, through the chalazal cap and plug as far as the boundary between the palisade and underlying mesophyll. During imbibition of water a kidney-shaped ‘blister’ was seen to rise, formed by separation of the palisade cells from an underlying single layer of subpalisade cells. The palisade layer forming the blister roof showed the same histochemical characteristic of other seed regions. The single layer of the blister floor showed an affinity with Toluidine Blue O and Alcian blue. Both blister roof and floor were strongly autofluorescent
Structural and histochemical investigation of the glandular trichomes of Salvia aurea L. leaves and chemical analysis of the essential oil
No full textAnatomical and histological investigations of the secretory hairs of Salvia aurea leaves, and identification of the main components of the essential oil were carried out. Two types of glandular trichome were found: peltate glands, characterized by a short stalk and a large six to eight-celled head, and capitate trichomes which were further subdivided into two kinds, the first with a short monocellular stalk and two-cellular head (type I), and the second with a multicellular stalk, a neck cell and a small globose unicellular head (type II). Whereas peltate glands and type I capitate trichomes were always present, type II capitate glands were not found in all leaf samples. The histochemical study suggested an 'endodermal' role for the stalk call (peltate and capitate type I) as well as for the neck cell (capitate type II), preventing the loss of essential oil. Histological reactions also revealed the complex nature of the material secreted by all types of S. aurea trichome, including polysaccharides, polyphenols and proteins, in addition to the essential oil. Qualitative and quantitative GC-MS analysis of the essential oil revealed camphor to be the main constituent. The findings are discussed in relation to studies of trichomes from other members of the Lamiaceae
Trichomes on vegetative and reproductive organs of Stevia rebaudiana (Asteraceae). Structure and secretory products
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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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