1,720,967 research outputs found
CARATTERIZZAZIONE CHIMICA E GEOCHIMICA DEI BIOINDICATORI VEGETALI
No full textQuesto studio si è posto l’obiettivo di valutare per mezzo di bioindicatori vegetali lo stato di contaminazione derivante dalla deposizione atmosferica di elementi potenzialmente tossici (EPT) nel territorio urbano e periurbano di Ravenna. A tal fine sono stati presi in considerazione un’area di interesse naturalistico, un’area a verde pubblico e un’area coltivata, scelti per la loro collocazione geografica secondo un gradiente di esposizione all’impatto antropico. La ricerca ha preso in esame 22 macro e microelementi valutati sia nel tessuto fogliare di piante vascolari che in muschi indigeni e la chimica degli isotopi radiogenici dello stronzio (Sr: 87Sr/86Sr) e del neodimio (Nd: 143Nd/144Nd) nei muschi. La caratterizzazione chimica di piante sempreverdi e decidue, eseguita in più campionamenti nell’arco di un anno, indica un andamento stagionale variabile dipendente dalla specie vegetale e dall’elemento indagato, se pur un accumulo di EPT si osservi specialmente in autunno. A differenza della concentrazione attuale che si riscontra nelle foglie, i muschi permettono di ricavare stime di possibili arricchimenti avvenuti nel corso degli anni. I fattori di arricchimento nei muschi indicano per diversi metalli, in particolare Cd, Cu, Sn e Zn, il superamento della soglia di contaminazione da severa a estrema, in diversi stazioni delle aree indagate. Si osserva una correlazione tra piante esposte ad intenso traffico veicolare e rilascio di Pt, sebbene la quota intercettata e ritenuta dalle lamine fogliari risulti non assorbita, rivelando la scarsa biodisponibilità di questo elemento. L’impiego dei muschi quali bioindicatori per definire le sorgenti naturali e antropiche del particolato atmosferico ha evidenziato che l’applicazione degli isotopi dello Sr e del Nd permette di ottenere importanti informazioni sui processi di inquinamento dell’aria dall’uso congiunto delle due sistematiche isotopiche.This study has been aimed at evaluating by means of plant bioindicators pollution resulting from atmospheric deposition of potentially toxic elements (PTE) in the urban and suburban areas of Ravenna. Therefore, three different areas were taken into account: an area of natural interest, a public green area and a cultivated area, chosen for their particular locations relative co anthropogenic impact. The research has determined 22 macro- and micro elements, both in the leaves of vascular plants
and native mosses, and the isotopic compositions of strontium (Sr: 87Sr/86Sr) and neodymium (Nd: 143Nd/144Nd) in mosses. The chemical characterization of evergreen and deciduous trees over a year time and their temporal trends indicate a seasonal pattern which depends on the plant species and the element investigated, although accumulation of PTE has been especially observed in the fall. Unlike concentrations measured in the leaves, mosses provide estimates of possible enrichment occurred over the years. For several metals, especially Cd, Cu, Sn and Zn, their enrichment factors in mosses show that the contamination threshold ranges from severe to extreme in several stations of the investigated areas. A correlation exists between the plants exposed to high vehicular traffic and the release of Pt, although the amount of Pt intercepted and retained by leaf blades results not to be absorbed, supporting the low bioavailability of this element. The use of mosses as bioindicators to define the natural and anthropogenic sourccs of the atmospheric particulate has shown that the joint application of Sr and Nd isotopes can provide important information on the air pollution processes
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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