1,721,032 research outputs found
Atomic Oxygen on Graphite: Chemical Characterization and Thermal Reduction
No full textThe chemisorption of O atoms on graphite and
the thermal reduction of the oxidized surface were studied by
means of high energy resolution photoelectron spectroscopy
with synchrotron radiation. The C 1s and O 1s core levels and
the valence band spectra were used to identify the different
oxidizing surface species and to evaluate the extension of the
sp2 conjugation as a function of oxidation time and annealing
temperature. We found that epoxy groups are the dominant
species only at the low oxidation stage, and ethers and
semiquinones form as oxidation proceeds. The evolution of
the ether/epoxy ratio with increasing oxygen coverage provides evidence for the occurrence of C−C bond unzipping. Epoxy
groups are the functionalities with the lowest thermal stability and start to desorb around 370 K, strongly affecting the desorption
temperature of other functional groups. The ratio between ethers and epoxy groups determines the balance between epoxy−
epoxy and epoxy−ether reactions, the latter promoting the removal of C atoms from the C backbone. Adsorbate spectroscopy
during thermal annealing definitely proves the catalytic effect of the basal plane oxygen atoms on the desorption reactions
Epitaxial Growth of Hexagonal Boron Nitride on Ir(111)
No full textThe formation of a hexagonal boron nitride (h-BN) layer through dissociation of borazine (B3N3H6) molecules on Ir(111) has been investigated by a combination of X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, temperature-programmed desorption, and lowenergy electron diffraction
Fundamental Role of the H-Bond Interaction in the Dissociation of NH_{3} on Si(001)-(2×1)
No full textFurther insight into the dissociative adsorption of NH3 on Si(001) has been obtained using a combined computational and experimental approach. A novel route leading to the dissociation of the chemisorbed NH3 is proposed, based on H-bonding interactions between the gas phase and the chemisorbed NH3 molecules. Our model, complemented by synchrotron radiation photoelectron spectroscopy measurements, demonstrates that the low temperature dissociation of molecular chemisorbed NH3 is driven by the continuous flux of ammonia molecules from the gas phase
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
Transfer-Free Electrical Insulation of Epitaxial Graphene from its Metal Substrate
No full textHigh-quality, large-area epitaxial graphene can be grown on metal surfaces, but its transport properties cannot be exploited because the electrical conduction is dominated by the substrate. Here we insulate epitaxial graphene on Ru(0001) by a stepwise intercalation of silicon and oxygen, and the eventual formation of a SiO2 layer between the graphene and the metal. We follow the reaction steps by X-ray photoemission spectroscopy and demonstrate the electrical insulation using a nanoscale multipoint probe technique
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