1,720,965 research outputs found
The postcranial of the deer Hoplitorneryx (Pliocene; Italy): another example of adaptive radiation on Eastern Mediterranean islands
Get PDFDurant el Pliocè, a l'illa de Gargano (costa sudest d'Itàlia) va evolucionar una fauna vertebrada altament endèmica. Aquesta fauna comprenia, entre d'altres, el eriçó gegant Deinogalerix, l'òliba gegant Tyto gigantea; el hàmster gegant Hattomys, i el cèrvol Hoplitomeryx amb cinc banyes i canins superiors en forma de sabre (tipus mòsquid). Els materials esquelètics d'HoplitomelYx formen un grup heterogeni, amb quatre classes de talla; dintre de les classes de talla poden estar presents diferents morfotipus. Totes les classes de talla comparteixen els mateixos trets típics d' Hoplitomeryx. Aquests són: una banya nasal central i un parell de banyes orbitals en punxa, canines sortints, fusió completa del navicocuboide amb el metatarsià, acanaladura metatarsiana distalment tancada, astràgal sense costats paral-lels, i una ròtula allargada. Les dife-rents classes de talla es troben repartides de forma igual a les fissures excavades, i a llavors no es poden considerar cronotipus. La hipòtesi d'un arxipèlag consistent en diferents illes on a cada una d'elles hi hagués un morfotipus no s'ha pogut confirmar, La situació de diferents morfotipus coexistint a una illa té un paral-lel amb Candiaceruus (Pleistocè, Creta, Gràcia). Les opinions sobre la seva taxonomia són diverses, i actualment prevaleixen dos models: un gènere per a vuit morfotipus o, alternativament, dos gèneres per a cinc espècies. El segon model només es basa en les proporcions dels membres, però aquestes són característiques taxonòmiques invàlides per als endemismes insulars, ja que canvien sota la influència de factors ambientals diferents dels continentals. També a Hoplitomeryx els morfotipus difereixen en les proporcions dels membres, però en aquest cas resulta improbable que provinguin de diferents ancestres, ja que en aquest cas els ancestres haurien d'haver compartit els trets hoplitomeríciids tipics. La morfoesfera d'Hoplitomeryx és massa coherent com per suposar dos a més ancestres, i indica un origen monofilètic de tots els morfotipus. En lloc d'això, la gran variació s'explica com a un exemple de radiació adaptativa, que va començar quan l'ancestre miocènic va colonitzar l'illa. Lespectre de ninxols buits degué promoure la seva radiació en diferents tipus tròfics, conduint a una diferenciació d' Hoplitomeryx. La manca compartida de mamifers depredadors grans i l'oferta limitada d'aliment a tots els ninxols degué promoure el desenvolupament de trets derivats secundaris a totes les classes de talla.During the Pliocene a highly endemic vertebrate fauna evolved on Gargano Island (south-east coast of Italy), comprising amongst others the giant hedgehog Deinogalerix, the giant barn owl Tyto gigantea, the giant hamster Hattomys, and the prongdeer Hoplitomeryx with five horns and sabrelike ('moschid' type) upper canines. The Hoplitomeryx skeletal material forms a he-terogenous group, containing four size groups; within the size groups different morphotypes may be present. All size groups share the same typical Hoplitomeryx features. These me: one central nasal horn and a pair of pronged orbital horns, protruding canines, complete fusion of the navicocuboid with the metatarsal, distally closed metatarsal gully, a nonparallel- sided astragalus, and an elongated patella. The different size groups are equally distributed over the excavated fissures, and are therefore not to be considered chronotypes. The hypothesis of an archipelago consisting of different islands each with its own morphotype cannot be confirmed. The situation with several co-existing morpho types on an island is paralleled by Candiacervus (Pleistocene, Crete, Greece). Opinions about its taxonomy differ, and at present two models prevail: one genus for eight morphotypes, or alternatively, two genera for five species. The second model is based upon limb proportions only, but these are invalid taxonomic features for island endemics, as they change under influence of environmental factors that differ from the mainland. Also in Hoplitomeryx the morphotypes differ in limb proportions, but here different ancestors are unlikely, because in that case they all ancestors must have shared the typical hoplitornerycid features. The morphosphere of Hoplitorneryx is too coherent to assume two or more different ancestors, and indicates a monophyletic origin of all morphotypes. The large variation is instead explained as an example of adaptive radiation, starting when the Miocene ancestor colonized the island. The range of empty niches promoted its radiation into several trophic types, yielding a differentiation in Hoplitomeryx. The shared lack of large mammalian predators and the limited amount of food in all niches promoted the development of secondary features in all size groups (apomorphies)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
