1,721,105 research outputs found
Photoluminescence of GaSe(Cu) Doped by Ion Implantation
No full textPhotoluminescence spectra of GaSe doped with Cu atoms by the ion implantation technique are reported. They are similar to spectra of GaSe doped by chemical methods. The analysis of spectra of crystals doped with different Cu concentrations confirms the defect level structure of GaSe(Cu) and also provides further evidence supporting the recombination kinetic model which explains the excitation intensity and temperature dependence of indirect excitonic lines
Photoluminescence Properties of Cu-doped GaSe
No full textPhotoluminescence spectra of undoped and Cu-doped crystals of the layered semiconductor GaSe have been measured in the temperature range from 80K to room temperature. The main modification of the spectra in doped crystals with respect to those of undoped samples is the appearance of two new bands and the enhancement of light emission. A detailed analysis of spectra, by varying excitation intensity and temperature, enabled the authors to analyse the defect levels involved in the transitions. A simple kinetic model for indirect free and bound excitonic transitions in doped samples is proposed
Anomalous Dips in Extinction Spectra of Disordered Carbon Grains
No full textUltraviolet extinction spectra of spongy agglomerates of amorphous carbon grains have been measured in the spectral range 100-300 nm. These spectra present two dips which can be explained in terms of harmonic resonant modes of electromagnetic waves in a disordered medium. This effect is due to the random fluctuations of the refraction index of our samples which have a disordered granular structure
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
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