1,721,009 research outputs found
Vibrational spectra and structures of neutral Si6X clusters (X = Be, B, C, N, O)
Get PDFDieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Neutral silicon clusters doped with first row elements (Si6X) have been generated (X = B, C, N, O) and characterized by infrared–ultraviolet (IR–UV) two-photon resonance-enhanced ionization spectroscopy (X = C, O) and quantum chemical calculations (X = Be, B, C, N, O, Si). In the near threshold UV photoionization, the ion signal of specific cluster sizes can be significantly enhanced by resonant excitation with tunable IR light prior to UV irradiation, allowing for the measurement of the IR spectra of Si7, Si6C, and Si6O clusters. Structural assignments are achieved with the help of a global optimization procedure using density functional theory (DFT). The most stable calculated structures show the best agreement between predicted and measured spectra. The dopant atoms in the Si6X clusters have a negative net charge and the Si atoms act as electron donors within the clusters. Moreover, the overall structures of the Si6X clusters depend strongly on the nature of the dopant atom, i.e., its size and valency. While in some of the Si6X clusters one Si atom in Si7 is simply substituted by the dopant atom (X = Be, B, C), other cases exhibit a completely different geometry (X = N, O). As a general trend, doping of the Si7 cluster with first-row dopants is predicted to shift the optically allowed electronic transitions into the visible or even near-IR spectral range due to symmetry reduction or the radical character of the doped cluster.DFG, FOR 1282, Controlling the electronic structure of semiconductor nanoparticles by doping and hybrid formatio
Vibrational spectra and structures of SinC clusters (n=3-8)
Get PDFThe effects of doping bare silicon clusters with carbon on their physical properties are of fundamental interest for the chemistry of the interstellar medium and the development of novel nanostructures in materials science. Carbon-doped silicon clusters (SinC, n = 3-8) are characterized in the gas phase with infrared-ultraviolet two-color ionization (IR-UV2CI) spectroscopy, mass spectrometry, and quantum chemical calculations. Structural identification is achieved by comparing the measured and calculated vibrational absorption spectra of the low-energy SinC isomers identified by global optimization algorithms. Except for planar Si3C, the most stable SinC clusters have three-dimensional configurations. While the Si3C and Si6C structures are uniquely assigned, several stable isomers of Si4C, Si5C, Si7C, and Si8C may co-exist under the present experimental conditions. Interestingly, some of the structures observed here are different from the ground state structures predicted previously. For the small neutral clusters (n <= 5), structures similar to those reported previously for the anions are observed. The highly stable Si3C unit with a nearly linear Si-C-Si motif is identified as characteristic building block in several of the most stable SinC structures. In all identified structures, a large negative charge of almost -2e is located on the C atom, indicating its role as electron donor in the Si-n host moiety. The B3LYP/cc-pVTZ level proves reliable in finding the experimentally observed isomers.EC/FP7/226716/EU/European Light Sources Activities - Synchrotrons and Free Electron Lasers/ELISADFG, FOR 1282, Controlling the electronic structure of semiconductor nanoparticles by doping and hybrid formatio
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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