1,720,970 research outputs found
Evaluación del uso de líquenes epífitos como bioindicadores indirectos de la calidad del aire en una zona rural y urbana de la comuna de Freire
No full textTesis (Licenciado en Biología)La contaminación aérea es un problema patente en zonas urbanas, que trae
consigo problemas para la salud de sus habitantes, además de evidentes
impactos en los ecosistemas y sus distintos niveles tróficos. Si bien las
metodologías de medición directa son efectivas, su alto costo y mantención las
vuelve poco habituales, por lo que se han implementado técnicas
complementarias a través del uso de bioindicadores para obtener resultados
indirectos, o downstream, de la calidad del aire. Uno de los más reconocidos a
nivel internacional son los líquenes epífitos, debido a su metabolismo y condición
simbiótica, presentan perturbaciones que pueden ser medibles para realizar
estudios de la condición atmosférica de manera indirecta, con técnicas
estandarizadas para condiciones templadas, con foco en el continente europeo.
No obstante, el uso de esta técnica es limitada por el nivel de los conocimientos
que se tenga tanto de la sensibilidad como de la resistencia de los líquenes
presentes en cada localidad analizada. Por estos motivos es relevante que
existan estudios que utilicen líquenes como medio para el monitoreo de la calidad
del aire, como también que se replique esta metodología en regiones. De esta
forma podríamos tener un indicador válido, reconocible y cuantitativo del impacto
en organismos vulnerables de la contaminación en sus ecosistemas. Como la
Región de la Araucanía está dentro de las más contaminadas del país, fue
seleccionada para implementar un estudio con líquenes epifitos; dónde se evaluó
la diversidad de líquenes en zonas con poca intervención antropogénica en
contraste con zonas más urbanizadas en la comuna de Freire. Aplicando el índice
de pureza ambiental, valores de diversidad liquénica complementado con
estudios multivariados, se confirma que los líquenes epifitos encontrados en la
comuna de Freire presentan cambios significativos dependiente de la condición
del ambiente que los rodea.Air pollution is an evident problem in urban areas, bringing along health issues for
their residents, as well as clear impacts on ecosystems and their various trophic
levels. While direct measurement methodologies are effective, their high cost and
maintenance make them uncommon, leading to the implementation of
complementary techniques using bioindicators to obtain indirect, or downstream,
results regarding air quality. One of the most internationally recognized
bioindicators is epiphytic lichens. Due to their metabolism and symbiotic condition,
they exhibit measurable disturbances that can be used for indirect atmospheric
condition studies, using standardized techniques for temperate conditions, with a
focus on the European continent.
However, the use of this technique is limited by the extent of knowledge regarding
the sensitivity and resistance of lichens present in each analyzed locality. For
these reasons, it is relevant for studies to exist that employ lichens as a means
for monitoring air quality, and for this methodology to be replicated in different
regions. This way, we could have a valid, recognizable, and quantitative indicator
of the impact of pollution on vulnerable organisms in their ecosystems. As the
Araucanía Region is one of the most polluted in the country, it was selected to
implement a study with epiphytic lichens. The diversity of lichens was evaluated
in areas with minimal anthropogenic intervention, contrasting with more urbanized
areas in the Freire commune. By applying the air purity index (IAP), values of
lichen diversity, along with multivariate studies, it is confirmed that the epiphytic
lichens found in the Freire commune exhibit significant changes depending on the
surrounding environmental conditions
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
Polysporina simplex (Davies) Vézda (Acarosporaceae, Ascomycota) new to Chile
No full textPolysporina simplex (Davies) Vézda es citada por primera vez para la flora criptogámica chilena. El material utilizado fue recolectado en el sector Ocoa en el Parque Nacional La Campana, en la zona central de Chile. La morfología, anatomía y química fueron revisadas y se entrega una descripción del material encontrado, su hábitat y distribución
Polysporina simplex (Davies) V?zda (Acarosporaceae, Ascomycota), nueva especie para Chile
No full textPolysporina simplex (Davies) V?zda es citada por primera vez para la flora criptogámica chilena. El material utilizado fuerecolectado en el sector Ocoa en el Parque Nacional La Campana, en la zona central de Chile. La morfología, anatomía yquímica fueron revisadas y se entrega una descripción del material encontrado, su hábitat y distribución.Polysporina simplex (Davies) V?zda es citada por primera vez para la flora criptogámica chilena. El material utilizado fuerecolectado en el sector Ocoa en el Parque Nacional La Campana, en la zona central de Chile. La morfología, anatomía yquímica fueron revisadas y se entrega una descripción del material encontrado, su hábitat y distribución
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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