1,721,056 research outputs found
Presentation and development of a physics experiment devised for didactic learning: The lambert-beer-bouguer law
No full textThe Lambert-Beer-Bouguer law refers to the decay of the intensity of a radiation travelling through a dissipative medium. Due to the simple phenomenology and to the easiness of the realization of an experimental apparatus for its verification and measure, such law represents, from a didactic point of view, a powerful tool to illustrate the basic features of the exponential decay behaviour to undergraduate students. This paper describes how such purpose can be reached by employing simple equipment and very accessible formalism
A recovered friend: The afocal system
No full textThe basic properties of a simple afocal optical system, namely a two-lens Keplerian telescope, are reviewed and compared with measurements that can be easily performed with instrumentation available in a university optical laboratory. The object-image conjugation, along with the Lagrangian invariant of the systems, are made clear by the comparison between theory and experiments, highlighting also the limits of the Gaussian approximation in the chosen experimental realization
Comparison of visual performance between a single and a dual-focus contact lens for the control of myopic progression
Full text linkMyopia is a globally widespread ametropia. This has motivated the
development of approaches to slow myopic progression, including the use of specific
dual-focus contact lenses for myopia control. In this study, the visual performance
of a dual focus contact lens (MiSightTM) and a single vision contact lens (Bausch
& Lomb Ultra) was compared. To this aim, 25 myopic subjects were recruited (Sp
from −0.50 D to −6.00 D, with max astigmatism of 1.00 CD). During the visit, the
monocular and binocular visual acuity without correction was recorded, and the total
topoaberrometry was performed. Subsequently, for each subject, monocular and
binocular low-contrast visual acuity and high-contrast visual acuity was addressed
with both type of lens. Visual quality was objectively evaluated by performing total
ocular aberrometry. The results allow evaluating the effect of dual focus contact
lens on vision
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
Design and test of a lens system for a high energy and high resolution electron spectrometer RID G-7348-2011
No full textWe describe the design and the laboratory test of an electrostatic input lens developed for high energy (> 5 keV) and high resolution photoelectron spectrometers. The lens is part of a hemispherical electron energy analyzer and is designed to optimize the overall accepted solid angle, taking into account the constraints due to the acceptance of the hemispherical dispersing element. In particular, the lens can be operated with two different polarization schemes enabling to obtain high and constant linear magnification (M-1 = 12 and M-1 = 20) in a large interval of retarding factor ranging from an acceleration of 5 to a retardation of 600 (dynamical range of 3000) by the same mechanical layout. These features make such an electrostatic input element a considerable improvement in the technical challenge to perform high quality experiments in high energy photoemission. (c) 2005 Elsevier B.V. All rights reserved
Ultrafast spectroscopy with spin polarization
No full textA project for the design and r.alization of an experimental station dedicated to ultrafast spin polarization dynamics allowing for spin polarization measurements of photoelectron yield as excited by free electron laser pulses is presented
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
Presentation and development of a Physics experiment devised for didactic learning: The Lambert-Beer-Bouguer law
No full textThe Lambert-Beer-Bouguer law refers to the decay of the intensity of a radiation travelling through a dissipative medium. Due to the simple phenomenology and to the easiness of the realization of an experimental apparatus for its verification and measure, such law represents, from a didactic point of view, a powerful tool to illustrate the basic features of the exponential decay behaviour to undergraduate students. This paper describes how such purpose can be reached by employing simple equipment and very accessible formalism
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
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