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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
ONE-DIMENSIONAL RANDOM POTENTIALS ALLOWING FOR EXTENDED STATES
No full textThe authors present a class of random potentials that allow for extended states at selected energies. These potentials can be obtained by starting from an underlying nondisordered potential and inserting in it in a random way particular potential profiles defined on a finite length. By making a suitable choice of the potentials to be inserted the energies of the extended states can be fixed arbitrarily
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
Absorption Spectra of GaAs/AlGaAs Random Superlattices at 2 K
No full textTransmission spectra of ordered and disordered GaAs/Al0.3Ga0.7As superlattices (SL) were measured at 2 K. The experimental results are compared with numerical simulations obtained by means of a transfer matrix method. The numerical results indicate that a multiple-quantum-well model accounts for the main features of random SL, and that a disorder-induced fine structure is present. The agreement between the measured spectra and the numerical calculations supports the predicted features
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