1,720,993 research outputs found
Direct Spectroscopic Evidence of the Mechanism behind the Phase Transition of [2,2]-Paracyclophane
No full text[2,2]-Paracyclophane undergoes phase transitions at 45 and 60K. Based on simultaneous Raman spectroscopy and inelastic neutron scattering experiments (12-70K), it was shown that a twisting motion of the ethylene bridge perpendicular to the plane of the aromatic rings drives the phase transition. The low-temperature (60K) conformers only differ by this twisting motion, which freezes out below 45K and is thermally averaged above 60K. Between 45 and 60K, the system gains energy until the phase transition is complete.DNRF; Villum Foundation; European Commission [283883, 283883-NMI3-II
In Situ Powder Diffraction Study of the Hydrothermal Synthesis of ZnO Nanoparticles
No full textZnO is one of the most widely applied nanomaterials, and the vast majority of ZnO nanoparticles are synthesized from aqueous solutions of inexpensive salts. Here we present the first in situ powder X-ray diffraction (PXRD) study of the formation of ZnO nanoparticles under hydrothermal conditions. An aqueous Zn(NO3)(2) and NaOH precursor gel was studied at three different temperatures (150, 200, and 250 degrees C) by in situ PXRD, and Rietveld refinements of the data were used to extract crystal structure and nanostructural information. Interesting trends in the evolution of crystallite size and twin faulting with temperature were established. The morphology of the synthesized crystallites depends on temperature and reaction time; at high temperatures and long reaction times almost isotropic crystallites are formed, while the anisotropy increases with shorter synthesis times and lower temperatures. Furthermore, the twin fault probability decreases with reaction time and increasing reaction temperature. Under the present synthesis conditions, a minimum ZnO crystallite size of around 14 nm in the a-direction and 22 nm in the c-direction is observed
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
Experimental determination of core electron deformation in diamond
No full textSynchrotron powder X-ray diffraction data are used to determine the core electron deformation of diamond. Core shell contraction inherently linked to covalent bond formation is observed in close correspondence with theoretical predictions. Accordingly, a precise and physically sound reconstruction of the electron density in diamond necessitates the use of an extended multipolar model, which abandons the assumption of an inert core. The present investigation is facilitated by negligible model bias in the extraction of structure factors, which is accomplished by simultaneous multipolar and Rietveld refinement accurately determining an atomic displacement parameter (ADP) of 0.00181 (1) Å2. The deconvolution of thermal motion is a critical step in experimental core electron polarization studies, and for diamond it is imperative to exploit the monatomic crystal structure by implementing Wilson plots in determination of the ADP. This empowers the electron-density analysis to precisely administer both the deconvolution of thermal motion and the employment of the extended multipolar model on an experimental basis
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
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