1,721,076 research outputs found
A Raman and FIR spectroscopic study of the solid solution (N(CH3)4)2ZnCl4-xBrx
Full text linkPolarized Raman and far-infrared spectra (10-350 cm-1) of the solid solution (N(CH3)4)2ZnCl4-xBrx are presented for several compositions (x = 0, 1, 2, 2.9 and 4) in the high- (300 K) and low- (60 K) temperature phases of the crystals. Apart from the internal modes of the ZnCl42- and ZnBr42- ions, several new active internal modes are found in the spectra, originating from the mixed (ZnCl4-nBrn)2- ions (n = 1, 2, 3 and 4). The spectra are in fair agreement with a simple 'free' ion model for the vibrational modes of the (ZnCl4-nBrn)2- ions. From the intensities of the tetrahedral ν1 modes, the relative concentrations of the various (ZnCl4-nBrn)2- ions in the crystals are estimated. Using these relative concentrations the value of x in the crystals is calculated, and found to be in good agreement with the stoichiometries of the crystal growth solutions. A pronounced low-frequency mode is observed in the spectra which scales with the average moment of inertia of the (ZnCl4-nBrn)2- ions, and is therefore assigned to a librational mode of these ions.
Dynamical and electronic properties of incommensurate and fullerene crystals
Full text linkContains fulltext :
mmubn000001_160101158.pdf (Publisher’s version ) (Open Access)Promotores : A. Janner, H. van Kempen en G. Meijer133 p
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
Identification of gaseous oxygen and nitrogen in bubble inclusions in Bi4(GeO4)3 (BGO) crystals by means of Raman spectroscopy
Full text linkBubble inclusions in BGO crystals have been studied by means of Raman spectroscopy. Since the crystals were grown under ambient atmospheric conditions, we focused our attention on oxygen and nitrogen. Both species are diatomic homonuclear molecules which are vibrationally and rotationally Raman active. Concerning the vibrational part of the O2 and N2 Raman spectra, no evidence was found for the presence of both gases. However, in the spectrum below the lowest 64 cm-1 energy mode of BGO three faint peaks were found which show the characteristic features of the rotational spectra of O2 and N2. It was found that the composition of the inclusion atmosphere was enriched by oxygen compared to the composition of the air.
Exciton dynamics in molecular aggregates
No full textThe fundamental aspects of exciton dynamics in double-wall cylindrical aggregates of cyanine dyes are studied by means of frequency resolved femtosecond pump-probe spectroscopy. The collective excitations of the aggregates, resulting from intermolecular dipole-dipole interactions have the characteristic property – the localization of the lowest lying exciton states. The experimentally observed outer-to-inner tubule excitonic energy transfer dynamics and the internal energy relaxation at low temperatures reveal a non-equilibrium population of the excitonic subsystem. The analysis of measured dynamics reveals very fast picosecond timescale energy relaxation to the optically active energy states.
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
- …
