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ESTUDIO TAXONOMICO DE LOS GENEROS NEOGONIOLITHON, SPONGITES Y PNEOPHYLLUM (CORALLINALES, RHODOPHYTA) EN LA COSTA DEL ATLANTICO DE MEXICO
No full textEstudio taxonómico de los géneros Neogoniolithon, Spongites y Pneophyllum (Corallinales, Rhodophyta) en la costa del Atlántico de México
Get PDFSISTEMATICA MOLECULAR DEL GENERO SARGASSUM (FUCALES, PHAEOPHYCEAE) EN COSTAS DEL ATLANTICO MEXICANO
Get PDFTaxonomía y distribución del género Hydrolithon (Foslie) Foslie (Corallinales, Rhodophyta) en México
No full textSe analizan y describen los caracteres utilizados en la descripción de las especies del género Hydrolithon (Corallinales, Rhodophyta) lo que evidencia la diferencia e inconstancia de su uso a largo de las investigaciones que publican los registros para nuestro país desde 1960. Con la información obtenida se reevalúan estos caracteres y se establecen los que se definen como importantes para separar las especies, entre las cuales se encuentran: hábito, superficie y construcción del talo, simetría, capas del epitalo e hipotalo, organización del hipotalo, presencia y disposición de los tricocitos, forma y disposición de las células de la región dorsal, células meristemáticas iniciales, forma y disposición de los conceptáculos, forma de las cámaras de los conceptáculos esporangiales, forma y disposición de las células del poro del conceptáculo, y la presencia de columela. Estos caracteres permiten establecer la presencia de 8 especies de Hydrolithon en México: H. boergesenii, H. farinosum, H. onkodes, H. pachydermum, H. reinboldii, H. rupestre, H. samoifnse e H. superficiale. De ellas, H. farinosum es la que se distribuye ampliamente en ambas costas, en contraste, las especies de distribución más restringida son: H. pachydermum e H. boergesenii, ambos en la región Sur del Golfo de México. Por otro lado, sólo fueron localizados en la costa Pacífica de México, H. rupestre, H. samoense e H. superficiale. Se proporciona la descripción detallada de cada especie, con fotografías y mapas de distribución. Esta información se complementa con una clave, notas de hábitat y comentarios taxonómicos.Characters previously used in the description of the species from the genus Hydrolithon (Corallinales, Rhodophyta) were analyzed and described using Mexican specimens from Atlantic and Pacific coasts. Results showed differences and inconstancies of their use throughout the published records from Mexico since 1960. In this paper sorne characters are defined as important to segregate species, among them are: habit, surface and construction of the thallus, symmetry, layers number in hypothallus and epithallus, organization of the hypothallus, trichocytes presence and arrangement, shape and arrangement of cells in the dorsal region, initial meristematic cells, shape and arrangement of conceptacles, chambers shape in sporangial conceptacles, cells shape and arrangement in the pore conceptacle, presence of columnella. The characters so evaluated allow to establish the presence of 8 species in Mexico: H. boergesenii, H. farinosum, H. onkodes, H. pachydermum, H. reinboldii, H. rupestre, H. somoense and H. superficiale. Hydrolithon farinosum is the one widely distributed on both coasts; in contrast, H. pachydermum and H. boergesenii are restricted to Southern Gulf of Mexico. 0n the other hand, H. rupestre and H. samoense were only located on the Pacific coast of Mexico. Detailed descriptions of each species, with photographs and distribution maps, are provided. This information is supplemented with a key and notes on habitat as well as taxonomic comments
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
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