1,720,969 research outputs found
Procedure for separating Fe from geological matrices to carry out isotopic analyses
No full textWe propose a simple procedure for separating and purifying Fe (and other metals) from geological matrices without the use of ionic exchange chromatography. This technique, in fact, may yield isotopic fractionation of the sample (Johnson and Beard, 1999; Schoenberg and von Blanckenburg, 2005). The sample is dissolved with HNO3 1.5 N to obtain a solution of pH between 2.5 and 3. Then, let H2S bubble through the solution for about 1 h, thus metal sulfides can precipitate completely under stationary conditions. After the solution is filtered and sul- fides are rinsed, they are dissolved with HCl 6 N. The different metals can be precipitated selectively by adding NH4OH and adjusting properly the pH. Lastly, the precipitates are filtered, rinsed and treated for carrying out TIMS analysis. To test effectiveness of the described procedure, the J–M iron standard was repeatedly analyzed. The isotopic results are shown in Table 1. It is evident that the analytical data obtained are of good quality, being particularly comparable with those carried out by Johnson and Beard (1999)
Sr isotopes and U series radionuclides in the Sangemini area (Central Italy): Hydrogeology implications
No full textThe strontium isotopic ratio (expressed as 87Sr/86Sr) of groundwater represents a useful method for studying and understanding the
groundwater circulations, also, the U and Ra isotopic compositions can vary as function of the groundwater residence time.
This paper reports an evaluation of the probable recharge area of the Sangemini mineral water springs (Terni-Umbria Central Italy)
and an estimate of the residence time of the aquifer by coupling Sr and U series isotopic systematics. For this study have been analyzed
four water sample for the isotope ratio of 87Sr/86Sr, and eleven samples, shallow waters and groundwaters, for U and Ra, furthermore
were determined the values of isotopic ratio for sample of typical rocks of the area. The results of this study allow to identify: a
recharge area in a restricted sector of the Meso-Cenozoic carbonates a longer and more effective water/rock interaction in the
Quaternary series. U and Ra recoil models allow to estimate a groundwater residence
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
Is Cyprideis agrigentina Decima a good paleosalinometer for the Messinian salinity crisis? Morphometrical and geochemical analyses from the Eraclea Minoa section (Sicily)
Full text link© 2014 Elsevier B.V. The living euryhaline species Cyprideis torosa (Jones) undergoes morphometric variations in size, noding and sieve-pore shape linked to the environmental salinity. In particular it is known that salinity values around 8-9 psu represent the osmoregulation threshold and also the turning point between smaller and greater valve dimensions and prevailingly noded against un-noded valves. The variation of the percentage of round-, elongate- and irregular-shaped sieve-pores on the valves has shown an empiric logarithmic correlation with the water salinity from 0 to 100 psu. Due to this ecologically cued polymorphism, C. torosa represents an invaluable paleosalinometer for the Quaternary brackish basins. In this paperwe attempt to verifywhether the ecophenotypical behavior of the post-evaporiticMessinian species Cyprideis agrigentina Decima was comparablewith that of Cyprideis torosa. To reach this goal, threemorphometric characters have been analyzed: 1) size variability; 2) noding and ornamentation; and 3) variability of the percentage of the sieve-pore shapes. The paleoenvironmental interpretation was made using synecological and geochemical approaches [stable isotopes, trace elements, Sr-isotopes and natural radioactivity (NRD)]. For this study, the 250 m-thick Messinian Lago-Mare succession of Eraclea Minoa (Agrigento, Sicily) was chosen for the presence ofmonotypic assemblagesmade only by C. agrigentina for around 70mof thickness. The results of the morphometric analyses showed that: 1) size variations are not related to the salinity changes recognized both from synecological and geochemical analyses; 2) no noded specimens have been recovered along the Section; 3) the salinities calculated on the basis of the percentage of the sieve-pore shape are not correlated with the salinities inferred from the synecological and geochemical analyses. Thus, in this paper we conclude that Cyprideis agrigentina cannot be considered a paleosalinometer for the Messinian Salinity Crisis. There is a correlation of the δ13C with the percentages of sieve-pore shapes, linking them to the behavior of the dissolved inorganic carbon (DIC) and to the oxygen availability at the bottom of the basin.The research of F.G. and E.G. has been founded by the Italian National Research Project PRIN 2009–2010. P.A. work is supported by Project CGL2011-23438.Peer Reviewe
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
The geological model of Celano town area for seismic microzonation activities
No full textIn this paper are presented the results of integrated investigations aimed at building a reference geological model for the seismic microzonation of Celano municipality (Central Italy). The study area is located along the northern rim of the Fucino basin, which is an intermontane half-graben filled by thick Plio-Quaternary alluvial and lacustrine deposits and is surrounded by Meso-Cenozoic limestone and Neogene sandstone relieves, with mean elevation around 1500m a.s.l., that also represent the bedrock units of the basin itself. Evidences of recent tectonic activity within the Fucino basin have been pointed out by several paleoseismological studies recently performed to better frame the effects of the seismogenic structures responsible for the Ms 7.0, 1915 Avezzano earthquake and other historical and prehistoric seismic events occurred in the area. On the basis of integrated site and laboratory investigations, such as surface geological surveys, borehole logging, isotope geochemical analyses based on Th-230/U-234 dating method, geotechnical investigation and hydrogeological prospecting, the geological model of the area was built. The identification of such model was fundamental in view of correct planning and development of further investigations and analyses, mainly based on geophysical methods and seismic response modelling, carried out by other research teams cooperating within the Celano seismic microzonation project. (C) 2008 Elsevier Ltd. All rights reserved
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