1,721,225 research outputs found
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
Evolution of Auger peaks in GaP(110) with hydrogen chemisorption
No full textAuger spectroscopy flanked by energy loss spectroscopy was used to investigate the evolution of GaP(110) surface electronic structure upon hydrogen exposure. The paper is focussed on the modification of PL(2,3)VV Auger line shape as a function of hydrogen exposure in the exposure range between zero and Ga3d surface exciton quenching. The discussion is concentrated on the Auger emission region about 9 eV below the emission from valence band top. The line shape change can be explained on the basis of present knowledge of electronic structure of H:GaP(110) surface and ascribed to the birth of a hydrogen-induced state (H-4) at similar to 4.4 eV below valence band top. Moreover the surface stoichiometry was monitored by Auger spectroscopy through the PL(2,3)VV to GaM(2,3)M(4,5)M(4,5) peak-to-peak ratio which was found to be extremely affected at high hydrogen exposures
Geo-mechanical characterization of carbonate rock masses by means of laser scanner technique
No full textKnowledge of the geometrical and structural setting of rock masses is crucial to
evaluate the stability and to design the most suitable stabilization works. In this work we use
the Terrestrial Laser Scanning (TLS) at the site of the Grave of the Castellana Caves, a famous
show cave in southern Italy. The Grave is the natural access to the cave system, produced by
collapse of the vault, due to upward progression of instabilities in the carbonate rock masses. It
is about 55-m high, bell-shaped, with maximum width of 120 m. Aim of the work is the
characterization of carbonate rock masses from the structural and geo-mechanical standpoints
through the use of innovative survey techniques. TLS survey provides a product consisting of
millions of geo-referenced points, to be managed in space, to become a suitable database for
the morphological and geological-structural analysis. Studying by means of TLS a rock face,
partly inaccessible or located in very complex environments, allows to investigate slopes in
their overall areal extent, thus offering advantages both as regards safety of the workers and
time needed for the survey. In addition to TLS, the traditional approach was also followed by
performing scanlines surveys along the rims of the Grave, following the ISRM
recommendations for characterization of discontinuity in rock masses. A quantitative
comparison among the data obtained by TLS technique and those deriving from the classical
geo-mechanical survey is eventually presented, to discuss potentiality of drawbacks of the
different techniques used for surveying the rock masses
Performing geo-mechanical characterization of carbonate rock masses in underground caves through Laser Scanner Technique
Full text linkTerrestrial Laser Scanning (TLS) survey provides a product consisting of millions of geo-referenced points, to be
managed in space, to become a suitable database for morphological and geological-structural analyses. Studying
by means of TLS a rock face, partly inaccessible or located in very complex environments, allows to investigate
slopes in their overall areal extent, thus offering advantages both as regards safety of the workers and time needed
for the survey. In karst environments, with particular regard to underground caves, the use of laser scanners might
become a very crucial tool to have the opportunity to cover logistically difficult sites. At the same time, TLS
alone cannot be used for a complete geo-mechanical characterization, but it needs to be integrated by specific
elaborations, addressed toward the identification and measurement of the main discontinuity sets in the rock mass,
and their interactions with the rock walls, depending upon the orientation of these latter.
In this contribution we describe the activities carried out at the site of the Grave of the Castellana Caves, a famous
show cave in Apulia, southern Italy. The Grave is the natural access to the cave system, produced by collapse of
the vault, due to upward progression of instabilities in the carbonate rock mass. It is about 55-m high, bell-shaped,
with maximum width of 120 m. Given the morphology of the wide bell-shaped cavern, and the overhanging walls
at several locations, there are some potential instability problems which needs to be carefully evaluated, since the
site is visited by a high number of tourists.
Through the use of the innovative TLS survey techniques, and detailed elaborations and analyses of the point
cloud, we were able to characterize the carbonate rock masses from the structural and geo-mechanical standpoints.
This work was further integrated and checked by the collection of field data through the classical approach, by
performing geological and structural surveys on rope and at the base of the cavern. The comparison among the
data obtained from different technique showed a good agreement, thus confirming the validity of the outcomes
from the TLS technique.
The final part of the contribution deals with the potential use of TLS technique in karst and underground
environments
The evolution of hydrogen induced defects and the restoration of π-plasmon as a monitor of the thermal reduction of graphene oxide
No full textIn this article, we study the modification of the optical, chemical and electronic properties of graphene oxide (GO) during thermal reduction in ultra-high-vacuum by combining the results of several electron spectroscopies. We find that the fraction of oxygen moieties on the surface, as deduced from the evolution of C 1s core level in photoemission, is progressively reduced upon increasing the annealing temperature from 150 to 650 °C. The intensity of the CH stretching mode, associated with CH defects on GO surface and measured in the low energy region of electron energy loss spectra (EELS), decreases as a function of the annealing temperature. The removal or the reduction of such hydrogen or oxygen defects induces a restoration of sp2 carbon hybridization. The presence of such hybridization is confirmed by the capability to excite π-plasmon as observed in the EELS spectra. In particular we find a critical annealing temperature (Tann = 300 °C) at which π-plasmon excitation via electron scattering is accessible suggesting the formation of graphene-like domains with size comparable with the plasmon wavelength (λp~5 nm). The linear dispersion of π-band close to Fermi level, as measured in UPS, confirms the formation of graphene-like domains
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
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