1,721,002 research outputs found
First record of the invasive algae Didymosphenia geminata in the Lake Nahuel Huapi: Argentina, Patagonia
Get PDFThe benthic diatom Didymosphenia geminata (L yngbye) M. Schmidt is a ver y aggressive invasive species found in riversand streams in different parts of the world. It has become a major concern for its tendency to form conspicuous blooms in oligotrophic aquatic systems with potential for detrimental impacts on recreational fi shing. Given its explosive development and the notable appearance in Lake Nahuel Huapi during the austral summer of 2013, our aim was to document the fi rst record for a large (557 km 2 ) lentic waterbody in the Andean Patagonia region.Fil: Beamud, Sara Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Baffico, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Pedrozo, Fernando Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; ArgentinaFil: Diaz, Monica Mabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentin
The Trophic state of Patagonian Argentinean lakes and its relationship with depth distribution in sediment Phosphorus
Get PDFThe parameters used to determine the trophic state of a water body are: total phosphorus (TP), transparency (Secchi disk depth) and chlorophyll a. However, these parameters show strong seasonal fluctuations which may hinder the estimation of trophic state. Some authors have proposed that sediments be used as an additional tool to evaluate the trophic state of a water body. The aim of this study was to determine the depth distribution of sediment TP in relation with the lake trophic state. Nine sediment corers from water bodies located in Patagonian Region (Argentina) were studied. The nutrient concentrations in pore water and in sediments were analyzed. The results obtained showed that there is a relationship between the depth distribution of sediment TP and the trophic state for all studied environments. Two exceptions were noted to this general pattern (Lakes Caviahue and Lácar). Our findings indicate that both pore water and sediments could be considered as the best parameters to estimate the tropic state of a water body compared to the water column.Fil: Temporetti, Pedro Felix. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; ArgentinaFil: Beamud, Sara Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; ArgentinaFil: Pedrozo, Fernando Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; 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
Sediment characteristics of the East Bay of Lake Lácar affected by sewage discharge
Get PDFVarios parámetros, físicos y químicos de la columna de agua, son usados para determinar el estado trófico de los ambientes acuáticos. Sin embargo, estos parámetros presentan fluctuaciones estacionales que podrían dificultar la clasificación trófica de un cuerpo de agua. La determinación de los componentes químicos de los sedimentos, complementada con los métodos de fraccionamiento del P, constituyen una herramienta con valor predictivo del estado trófico de los ambientes acuáticos. El objetivo de este trabajo fue evaluar el aporte de las aguas residuales (principalmente fósforo) sobre la calidad de los sedimentos de un lago oligotrófico patagónico (Lago Lácar, San Martín de los Andes, Neuquén), y determinar la influencia sobre la distribución del P en relación con los elementos que controlan su disponibilidad. Los resultados de la química y experiencias de fijación/liberación de P realizadas indican la existencia de una liberación de P desde los sedimentos hacia la columna de agua, fundamentalmente en la zona central de la bahía, lo que origina una carga interna.Several physical and chemical parameters of water column are used to determine the trophic status of aquatic environments. However, these parameters show strong seasonal fluctuations that might hinder the trophic classification of a water body. The determination of the chemical components of sediments, supplemented with P fractionation methods could provide a tool with predictive value of trophic status of aquatic environments. The aim of this study was to evaluate the effect of wastewater (phosphorus primarily) on the quality of the sediments of a Patagonian oligotrophic lake (Lake Lácar, San Martin de Los Andes, Neuquén), and determine the influence on the distribution of P in relation to the elements that control its availability. The chemical results and fixation/release experiences of P performed indicate the existence of P release from the sediments into the water column, mainly in the central area of the bay, causing an internal load.Fil: Temporetti, Pedro Felix. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; ArgentinaFil: Antonuk, Lidia. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; ArgentinaFil: Pedrozo, Fernando Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; 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
Lithological and hydrological controls on water composition: evaporite dissolution and glacial weathering in the south central Andes of Argentina (33-34° S)
Get PDFLithological and hydrological influence on fluvial physical and chemical erosion was studied in a glacierized sedimentary basin with high evaporite presence. Suspended particulate matter (SPM), total dissolved solids (TDS) and major ion concentrations were analyzed for two years of different hydrologic condition: i) 2009-2010, Q = 100% average; and ii) 2010-2011, Q = 60% average. Annual hydrograph was simple regime ? type with one peak in summer related to snow melting. The intra-annual SPM and TDS variations were directly and inversely associated to Q, respectively. Snow chemistry showed continental influence (Na+/Ca2+=0.17) and atmospheric input of TDS was <1% of the total exported flux. River water was highly concentrated in Ca2+ and SO42- (~4 mmol L-1) and in Na+ and Cl- (~3 mmol L-1). Ca2+/SO42- and Na+/Cl-¬ molar ratios were ~1 and related to Q; directly and inversely, respectively. Major ion relationships suggest that river chemistry is controlled by evaporite (gypsum and halite) dissolution having a summer input from sulphide oxidation and carbonate dissolution, and a winter input from subsurface flow loaded with silicate weathering products. This variation pattern resulted in nearly chemostatic behavior for Ca+, Mg2+ and SO42- while Na+, Cl- and SiO2 concentrations showed to be controlled by dilution/concentration processes. During 2009-2010 hydrological year the fluxes of water, SPM and TDS registered in the snow melting ? high Q season were, respectively, 71%, 92% and 67% of the annual total; while for equal period in 2010-2011, 56% of water, 86% of SPM and 54% of TDS annual fluxes were registered. The SPM fluxes for 2009-2010 and 2010-2011 were 1.19 106 t y-1 and 0.79 106 t y-1; while TDS fluxes were 0.68 106 t y-1 and 0.55 106 t y-1, respectively. Export rates for 2009-2010 were 484 t km2 y-1 for SPM and 275 t km2 y-1 for TDS. These rates are higher than those observed in glacierized granite basins and in non-glacierized evaporite basins, suggesting a synergistic effect of lithology and glaciers on physical and chemical erosion.Fil: León, José Gabriel. Provincia de Mendoza. Departamento General de Irrigación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pedrozo, Fernando Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Estudio en Calidad de Aguas y Recursos Hídricos; Argentin
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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