1,721,148 research outputs found
Efficiency of gratings in the conical diffraction mounting for an EUV time-compensated monochromatorProceedings of SPIE
No full textRecent measurements of the absolute diffraction efficiency of plane gratings in the conical diffraction mounting (in which the light approaches the grating in the plane parallel to the direction of the grooves) are presented. Three gratings have been tested at the beamline BEAR (Elettra Synchrotron, Trieste) in the 10-130 nm region, showing a peak efficiency as high as 70%. The aim of these measurements is the use of two gratings in the conical diffraction mounting for the realization of a high-throughput time-compensated monochromator for the spectral selection of high-order harmonic radiation produced by the interaction between an ultrashort laser pulse (less than 100 fs) and a gas jet. The monochromatic and ultrashort pulse at the monochromator exit can be used for the injection of a Free Electron Laser. The theory of the time-compensation with gratings will be briefly resumed, the design of the monochromator will be presented, and the results of the measurements at BEAR will be discussed
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
Publisher Correction: Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source
Full text linkIn the original version of this Article, the affiliation for Luca Poletto was incorrectly given as ‘European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Hamburg, Germany’, instead of the correct ‘CNR, Istituto di Fotonica e Nanotecnologie Padova, Via Trasea 7, 35131 Padova, Italy’. This has now been corrected in both the PDF and HTML versions of the Article
Attosecond pulses for the investigation of ultrafast electronic processes
No full textTo give a classical physics perspective a few tens of attoseconds corresponds roughly to the
time an electron spends on the first Bohr orbit in the hydrogen atom to complete its revolution
around the nucleus. In the same time interval the electric field of an optical pulse makes a small
fraction of its oscillation. The physics at such short time scales represents a great challenge both
for theory and experiment and can provide amazing results
Publisher Correction: Coherent diffractive imaging of single helium nanodroplets with a high harmonic generation source (Nature communications (2017) 8 1 (493))
Full text linkIn the original version of this Article, the affiliation for Luca Poletto was incorrectly given as 'European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Hamburg, Germany', instead of the correct 'CNR, Istituto di Fotonica e Nanotecnologie Padova, Via Trasea 7, 35131 Padova, Italy'. This has now been corrected in both the PDF and HTML versions of the Article
- …
