1,720,990 research outputs found
Molecular identification of root fungal associates in Orchis pauciflora Tenore
No full textThe terrestrial orchid, Orchis pauciflora Ten., growing in poor grassland and garrigue of Central Mediterranean region, is
local and rare and has been included in the red lists of several Italian regions. We investigated the diversity of fungal
associates in O. pauciflora adult plants collected in two protected areas of Tuscany (Central Italy). Genomic DNA was
extracted from mycorrhizal roots of 12 orchid plants and the fungal ITS were amplified and sequenced. Several fungal
associates, belonging to different taxa of basidiomycetes (Tulasnellaceae) and ascomycetes such as Leptodontidium, Exophiala
and Phialophora species, were recovered. The trophic role of these fungi and their impact on O. pauciflora growth and
conservation are discussed
Theoretical study of building blocks for molecular switches based on electrically induced conformational changes
No full textWe present an investigation of building blocks for molecular torsional switches made up of two distinct aromatic moieties, possibly bonded through one or more acetynil groups. The mechanism of operation is based on the action of a static electric field perpendicular to the ring-ring bond, which can modulate the torsional angle and, as a consequence, the inter-ring conjugation. The action of the perpendicular electric field on the dihedral angle is shown to increase, as a result of the inclusion of suitable substituents on the aromatic rings. By computing the response of the electron density of a molecule, with an excess electron, to a longitudinal electric field, we show that the intramolecular electron transfer is sensitive to the torsional angle. This feature can be conveniently rationalized in terms of a potential barrier which is created along the molecule as the dihedral angle varies from the co-planar to the perpendicular position
Conductance modulation in molecular devices via field-induced conformational change
No full textWe present a new class of possible molecular torsional switches tuned by an external electric field. We have performed a theoretical investigation of the action of a transverse electric field on the ring-to-ring charge transfer for a class of molecules made up of two distinct aromatic moieties, bonded through an acetylene group
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
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