1,720,973 research outputs found
Conductance fluctuations in Si nanowires studied from first-principles
No full textWe study how the variability of the conductance associated with single-dopant configurations affects the overall conductivity of long, realistic ultrathin Si nanowires (NW). We calculate the resistance associated with each single-dopant configuration from density-functional theory (DFT) calculations and we sum them up classically to obtain the resistance of the long wire. This allows to identify limiting factors for the performance of Si NWs based devices
Structural and electronic properties of Si1-xGex alloy nanowires
No full textWe present first-principles density-functional calculations of Si1-xGex alloy nanowires. We show that given the composition of the alloy, the structural properties of the nanowires can be predicted with great accuracy by means of Vegard’s law, linearly interpolating the values of a pure Si and a pure Ge nanowire of the same diameter. The same holds, to some extent, also for electronic properties such as the band-gap. We also assess to what extend the band-gap varies as a function of disorder, i.e., how it changes for different random realization of a given concentration. These results make possible to tailor the desired properties of SiGe alloy nanowires starting directly from the
data relative to the pristine wires
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
THEORETICAL STUDIES OF ABSORPTION, EMISSION AND GAIN IN SILICON NANOSTRUCTURES
No full textDensity-functional and many body perturbation theory calculations have been carried out in order to study the structural, electronic, and opti- cal properties both in ground and excited state configuration, of silicon nanocrystals in different conditions of surface passivation and doping. Starting from hydrogenated clusters, we have considered different Si/O bonding geometries at the interface. We provide strong evidences that not only the quantum confinement effect but also the chemistry at the interface has to be taken into account in order to understand the phys- ical properties of these systems. In particular we show that only the presence of a surface Si-O-Si bridge bond induce an excitonic peak in the emission-related spectra, redshifted with respect to the absorption onset, able to provide an explanation for both the observed Stokes shift and the near-visible photoluminescence (PL) experimentally observed in Si-nc. For the silicon nanocrystals embedded in a SiO2 matrix, the electronic and optical properties are discussed in detail. The strong in- terplay between the nanocrystal and the surrounding host environment and the active role of the interface region between them is pointed out, in very good agreement with the experimental results. Finally, concerning doping, we will show that, thanks to electronic transitions between donor and acceptor states present at the band edges and considering also the effect of quantum confinement it is possible to engineer the absorp- tion and emission spectra of Si nanocrystals. For each considered system optical gain calculations have been carried out giving some insights on the system characteristics necessary to optimize the gain performance of Si-nc
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
