1,721,140 research outputs found
Novel Determination of Elemental Mercury in Silicate Rock by Thermal Desorption
No full textMuch importance has been given in the recent literature to the determination and speciation of mercury in contaminated mine waste and soil. Among mercury species, the concentration of elemental mercury is a key parameter for risk assessment. However, at present, a validated analytical method for the quantitation of Hg(0) in solid matrices does not exist. In the present study, the reliability of a thermal desorption technique in quantifying elemental mercury in Hg(0) amended silica glass, a reference shelf standard, and in a Hg(0)-bearing mineralized silicate rock, considered representative of mine tailings, has been addressed. Mercury release has been measured at variable temperature using a thermo-desorption method combined with a mercury vapor analyzer. The results allowed the peak temperature for the emission of free and matrix-bound Hg(0) components to be identified, suggesting that 100 degrees C represents a suitable temperature for Hg(0) isothermal release. Experiments with the shelf standard exposed to a specific sorbent keeping the temperature constant at 100 degrees C provided 90% and 98% Hg(0) recovery after 2 and 24 h, respectively. Experiments with the mineralized rock demonstrated that free elemental mercury was recovered after 6 h, while 60 h were required for the free and matrix bound Hg(0) release. The limits of detection and quantification of the method were 1.3 ng and 3.0 ng, respectively. This approach allows elemental mercury in solid matrices to be determined, allowing the quantification of Hg(0) in contaminated mine tailings and soil
Thallium Contamination in the Raibl Mine Site Stream Drainage System (Eastern Alps, Italy)
No full textThe Raibl mine (Cave del Predil village,
northern Italy) belongs to the Pb–Zn minerogenetic district
in the southeastern Alps, hosted in Middle Triassic carbonates.
The drainage water quality reflects the high acidbuffering
capacity of the carbonate rocks, which controls
the mobility of most metals. In particular, Fe is non-detectable
in solution, having formed hydrous-oxides precipitates.
Molybdenum, Ni, Zn, Cd, Pb, and Tl are present,
and the Pb, Tl, and Zn concentrations sometimes exceed
the Italian regulatory thresholds. Thallium concentrations
substantially exceed the 2 lg/L limit at some sampling
stations, ranging between 12 and 30 lg/L in the mine
drainage, and reaching 5 lg/L downstream of the mine
site, despite strong dilution. The data indicate that Tl behaves
almost conservatively and is not significantly scavenged
by the Fe precipitates. The elevated Tl represents a
potential risk for the stream ecosystem. Although Tl is not
regulated in drinking water in Italy or the European
Community, its distribution in natural waters may help to
determine if health actions should be taken
Analisi di elementi maggiori, minori e tracce in rocce e minerali mediante spettrometria sequenziale con Plasma ad Accoppiamento Induttivo
No full textdescrizione di una metodologia analitica per rocce e mineral
La sistematica isotopica dello Sr come tracciante dei circuiti idrologici: il bacino del Flumendosa (Sardegna meridionale, Italia)
No full textThe distribution of paramagnetic centers in glass and lavas from eruptive activity at Mt. Etna: implications for magmatic processes during basaltic eruptions
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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