1,721,057 research outputs found
Possible fluctuation origin of the anomalies in the C-axis magnetoresistance observed in bi2sr2cacu2o8+x above the critical-temperature
No full textAn expression for the transverse magnetoresistance above T-c has been derived from the theory of fluctuation contribution to the c-axis conductivity of layered superconductors under an external magnetic field,, which was recently developed by Dorin et al. The suppression of fluctuations due to the magnetic field leads to a decrease of the negative fluctuation contribution to the conductance, and therefore to a negative transverse magnetoresistance at temperatures not too close to T-c. The formula derived from the theory has been compared with the available experimental data of the magnetoresistance of BSCCO single crystals obtained by Ong et al. at temperatures 10-20 K above T-c. The quadratic increase of the relative magnetoresistance with the field and its temperature dependence are explained clearly. A quantitative fit to the experimental data shows a remarkable agreement of the theory with experiment, and allows to extract the values of several physical parameters
On the character of the fluctuating diamagnetism above the superconducting transition in La1.9Sr0.1CuO4
No full textIsothermal magnetization curves above the transition temperature T-c in a single crystal of superconducting underdoped cuprate La1.9Sr0.1CuO4 are reported. In the low-field range, H <= 1 kOe, and for T within Tc + 2 K, evidence is given of a fluctuating diamagnetism different from the one expected from the Ginzburg-Landau theory infinite fields. The experimental findings are related to phase fluctuations of order parameter in "droplets" having local Tc(loc) higher than the bulk resistive Tc, a general phenomenon in cuprates and intrinsic consequence of charge inhomogeneities at mesoscopic level. The temperature dependence of the droplets size suggests a percolative character of the transition
Superconducting fluctuations and anomalous diamagnetism in underdoped YBa2Cu3O6+x from magnetization and Cu-63 NMR-NQR relaxation measurements
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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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