1,721,010 research outputs found
Ion and electron beam nanofabrication of the which-way double-slit experiment in a transmission electron microscope
No full textWe have realized a which-way experiment closely resembling the original Feynman’s proposal exploiting focused ion beam milling to prepare two nano-slits and electron beam induced deposition to grow, selectively over one of them, electron transparent layers of low atomic number amorphous material to realize a which way detector for high energy electrons. By carrying out the experiment in an electron microscope equipped with an energy filter, we show that the inelastic scattering of electron transmitted through amorphous layers of different thicknesses provides the control of the dissipative interaction process responsible for the localization phenomena which cancels out the interference effects
Multiple beam interference and diffraction with FIB fabricated nano-slits
No full textThe recent advances in nanotechnology and electron microscopy are making today possible the realization of experiments of diffraction and interference at multiple slits which formerly were carried out with extremely skilled specimen preparation techniques and dedicated electron optical apparatus [1]. Recently we have used the focused ion beam (FIB) to fabricate two slits on a commercial silicon nitride membrane (500 nm thick) suspended on a 100x100m2 silicon frame 200m thick. In that case the Fraunhofer image was observed in a conventional TEM-JEOL 2010 [2].Here we adopt a less expensive support for nano-slits fabrication, consisting of a commercial continuous carbon film on a standard copper grid, which was subsequently coated with a gold layer about 120 nm in thickness. The slits (nominally 80nm wide, 420 nm spaced) were fabricated with a 9 pA, 30keV, Ga+ beam of a FEI Strata235M Dual Beam. The quality of the slits is very good, as shown in Fig. 1(a) and Fig.1(b), that display two and three slits, respectively. An additional advantage of these samples with respect to the previous ones, is that they can be inserted in almost all FEG-TEM specimen holders. The diffraction and interference experiments were carried out with a JEM-2200FS electron microscope. Owing to the larger coherence of the FEG with respect to the thermionic source, it has been possible to record interference and diffraction images with exposure times of few seconds.The three-slit case is illustrated in Fig. 2 where the in focus image (a), and the images taken at a nominal defocus of -10 mm (b), -20 mm (c) and -40 mm (d), are reported. This sequence shows the transition from the nearly separated Fresnel diffraction images of the single slits, (b), to their subsequent overlapping as the defocus increases, displaying interference phenomena, (c), and finally to a nearly Fraunhofer image, (d).Fig. 3 displays the true Fraunhofer image, taken at a nominal defocus of -53 mm, which clearly shows the secondary minima between the more intense maxima. In the same figure the single slit Fraunhofer images corresponding to the longer side of the slits can also be observed
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
Irreversible weak limits of dynamical systems
No full textDottorato di ricerca in fisica. A.a. 1998-99.Relatore Giorgio Velo. Coordinatore Giulio Pozzi. Correlatore Giovanni MorchioConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
Observation of an anomalous semileptonic decays of heavy flavor quarks in pp interactions at 1.8 TeV
No full textDottorato di ricerca in fisica. 12. ciclo. A.a. 1998-99. Coordinatore Giulio Pozzi. Tutore Antonio RossiConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
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
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