1,720,959 research outputs found
DISTRIBUTION OF ELEMENTS IN ICE CORE SAMPLES OF THE LAST 30000 YEARS
No full textThe concentrations of several elements ( Na, Mg, Al, Si, P, S, Cl, K, Ca Ti, Cr, Mg, Fe, Co, Ni, Cu, Zn) were measured in the insoluble fraction of ice samples from an Anctartic ice core of about 700 m depth. The insoluble particles were collected by filtration from melted samples. The element concentrations were determined by PIXE (Particle Induced X-ray Emission) with measurement errors generally lower than 10%. The concentration trends were related to temperature profile, obtained from the behavior of D (that dated about 30000 years over the core), to compare the climate variability with the precipitation composition
TRACE ELEMENTS IN SPRING WATER FROM NORTHERN APENNINES (ITALY)
No full textChemical/physical parameters and trace element concentration measured in spring water from Northern Apennines (Italy) are presented
Elemental and mineral characterisation of coastal antarctic aerosols in snow using PIXE and SEM-EDAX
No full textThe chemical constituents of snow from a 3 m pit sampled at a coastal Antarctic site were characterised by means of PIXE and SEM-EDAX. Oxygen isotope dating revealed that the pit spanned an 8-year period. from 1986 to 1994. Concentrations measured by PIXE ranged from less than 1 ng g(-1) of H2O for Cu, and Zn to several tens of ng g(-1) for Si, S and Cl. The major elements found were Si, S, Al, and Na, which contributed more than 75% of the element loading. Snow layers with elevated Cl concentration were regularly found along the pit. The mineralogy of the insoluble particles determined by SEM-EDAX analyses showed that quartz, plagioclase and clays were the prevalent minerals. The proportion of each element in the insoluble phase was comparable with that previously found in similar studies. (C) 1999 Elsevier Science B.V. All rights reserved
DEVELOPMENTS IN ENVIRONMENTAL RESEARCH OF FISAMB MO PIXE GROUP
No full textTHE DEVELOPMENTS IN ENVIRONMENTAL RESEARCH ACTIVITY AT LNL OF FISAMB MO PIXE GROUP ARE PRESENTE
PIXE ANALYSIS OF MAJOR AND TRACE ELEMENTS IN ANTARCTIC ICE SAMPLES FROM EPICA
No full textMAJOR AND TRACE ELEMENTS HAVE BEEN DETERMINED BY PIXE IN ANTARCTIC ICE SAMPLES FROM EPICA ICE CORE
ELEMENTAL COMPOSITION DETERMINED BY PIXE ANALYSIS OF THE INSOLUBLE AEROSOL PARTICLES IN EPICA-DOME C ICE CORE SAMPLES REPRESENTING THE LAST 27000 YEARS
Full text link107 samples from the first 581 m of the EPICA ice core, Dome C, East Antarctica, representing a 27000 year record, were analysed by the PIXE technique. The concentrations of several elements (Na, Mg, Al, Si, S, Cl, K, Ca, Ti, Mn, Fe) were determined in the insoluble particles, collected by filtration from the melted ice samples. The average elemental ratios for Holocene and LGM are in agreement with continental crust values. The element depositional fluxes, evaluated from PIXE concentration data by means of the EPICA ice accumulation rate, are smaller in the Holocene than during Glacial times, confirming the differences in dust loads in the atmosphere during the contrasting climatic conditions. In Holocene, the fraction of the insoluble particle mass (estimated as the sum of the measured element oxides) agrees well with the total dust mass as determined from Coulter Counter measurements, but during the LGM the particle counting shows a larger dust mass
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
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