1,720,979 research outputs found
Granos de polen de angiospermas de la Formación Punta del Barco (Aptiano), provincia de Santa Cruz, Argentina
No full textSe reporta una nueva localidad fosilífera para la Formación Punta del Barco, y se describen los resultados preliminares del estudio palinológico de una asociación polínica con granos de polen de afinidad angiospérmica. El género mejor representado es Clavatipollenites, al que acompaña Monocolpopollenites, además de otros granos esporádicos con esa misma afinidad, todos ellos mencionados por primera vez para esta unidad litoestratigráfica. Este grupo polínico presenta una llamativa diversidad en los tipos aperturales para la edad de los sedimentos, acotada mediante métodos radimétricos.Fil: Llorens, Magdalena. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
New age of the base of the Chubut Group at the Cerro Solo uranium reservoir, Chubut Province
Get PDFEn este trabajo se analizan las características litológicas de la roca hospedante de la mineralización de uranio del yacimiento Cerro Solo, que corresponde al miembro inferior de la Formación Los Adobes, unidad basal del Grupo Chubut en su sector norte. Se analiza la asociación de polen angiospérmico de allí recuperada, y en base a ese análisis, se establece una edad albiana temprana para la asociación polínica, que determina una edad más joven que la considerada hasta el momento para el inicio de la depositación de las sedimentitas del Grupo Chubut en el depocentro del yacimiento Cerro Solo.This paper analyzes the lithological characteristics of the uranium mineralization host rocks from Cerro Solo reservoir, corresponding to the lower member of the Los Adobes Formation, basal unit of the Chubut Group in its northern sector. The angiosperm pollen association there recovered is analyzed. According with this analysis, an early Albian age for the pollen association is established, that determines a younger age than that considered until now for the beginning of deposition of the Chubut Group sediments at the Cerro Solo reservoir depocentre.Fil: Marveggio, Nilda. Comision Nacional de Energia Atomica. Regional Patagonia; ArgentinaFil: Llorens, Magdalena. Comision Nacional de Energia Atomica. Regional Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin
Field key for recognizing frequent herbs and shrubs of the monte Patagónico, Argentina
Get PDFLa presente clave proporciona una herramienta para el reconocimiento a campo de las especies más frecuentes del Monte Patagónico. Abarca108 especies del monte austral, que comprende las regiones del noreste de Chubut y el sudeste de Río Negro, y fue elaborada en base a las formas biológicas que presentan las plantas y los caracteres vegetativos y reproductivos de mayor relevancia.Permite reconocer 1 especie de gimnosperma, 3 especies de helechos, 86 especies de eudicotiledóneas (incluyendo 5 especies de cactus y 3 árboles) y 18 especies de monocotiledóneas.This key provides a tool for recognition field of the most common species of Patagonian Mont. It covers 108 species of the southern mountain, comprising the northeastern regions of Chubut and Southeast Black River, and was developed based on biological forms that present plants and vegetative and reproductive traits more relevant. We can recognize 1 species of gymnosperms, 3 species of ferns, 86 species of eudicotiledoneas (including 5 species of cactus and 3 species of trees) and 18 species of monocots.Fil: Llorens, Magdalena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "san Juan Bosco". Facultad de Cs.naturales - Sede Trelew. Departamento de Biología; ArgentinaFil: González, Cynthia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "san Juan Bosco". Facultad de Cs.naturales - Sede Trelew. Departamento de Biología; Argentin
Late Aptian angiosperm pollen grains from Patagonia: earliest steps in flowering plant evolution at middle latitudes in southern South America
Get PDFThe angiosperm pollen record from the Anfiteatro de Ticó and Punta del Barco formations (Baqueró Group) is reported. The relevance of these floras is that they are accurately dated as late Aptian, and one of the oldest floras southern South America with fossil angiosperms. Twelve samples were studied, showing Clavatipollenites and Retimonocolpites as dominant types. A new species, Jushingipollis ticoensis sp. nov., is proposed. A doubtful angiosperm pollen grain, Lethomasites sp., is also identified and described. A multivariate analysis of similarities between different Early Cretaceous angiosperm pollen assemblages suggests that the Baqueró Group assemblages have great similarities with other coeval units from Argentina, Australia and United States, which were located in a similar paleolatitude.Fil: Llorens, Magdalena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Trelew; ArgentinaFil: Perez Loinaze, Valeria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentin
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
First megafloristic record for the Chubut Group at Somuncurá Canadón Asfalto Basin: An angiosperm dominated flora from the Upper Cretaceous Puesto Manuel Arce Formation, Patagonia Argentina
Get PDFThe first association of fossil plantimpressionsin the Chubut Group at the Somuncurá-Cañadón Asfalto Basin is described herein. Themid-Cretaceous megafloral assemblage from Patagonia, Argentina was recovered from the Puesto Manuel Arce Formation.The taphocenosis consists mostly of leaves preserved as impressions, although a variety of cuticle remains are also present. Angiosperms are both quantitatively and qualitativelythe main component of the flora (at least 9 leaf morphotypes recognized). A few ferns and conifers complete the plant assemblage.The angiosperm leaves exhibit physiognomic heterogeneity with a variety of well-defined venation patterns.The myrtophyll morphotype (Myrtoidea sp.) and palmatilobed palinactinodromous leaves (Bamfordphyllum crassivena gen. et sp. nov.) are significant components of the assemblage. Flora characters are consistent with the Cenomanian - earliest Turonianage proposed for the Puesto Manuel Arce Formation. Comparisons were made with coeval Patagonian and extra-regional floras which suggest both local as well as long-distance gondwanan links.Fil: Passalia, Mauro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Llorens, Magdalena. Comision Nacional de Energia Atomica. Centro Atomico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Páez, Manuel Antonio. Comision Nacional de Energia Atomica. Centro Atomico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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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