305,229 research outputs found
Reflection solitons supported by competing nonlinear gratings
No full textWe analytically investigate solitons counterpropagating in a longitudinally modulated Kerr medium by means of the Hirota bilinear approach. We show that Hirota solvability (partial integrability of the system) physically corresponds to the exact mutual cancellation of the effects of all the underlying nonlinear gratings. This cancellation is achieved in two different situation: either through a suitable choice of the field profile or by means of a peculiar tailoring of the nonlinear modulation. In the first situation we obtain both bright and dark one-soliton solutions whose intensity ratio between forward and backward propagating beams is set by the nonlinear modulation. In the second situation, we derive two-soliton solutions obtained by nonlinearly dressing two independent linear grating eigenmodes sharing the same propagation constant
Fiber-launched ultratight solitons integrating fast soliton-based beam manipulation circuitry
No full text
Caratterizzazione ampelografica e molecolare di vitigni minori del Lazio
No full textVengono riportati i risultati della caratterizzazione ampelografica, ampelometrica e molecolare di 36 accessioni appartenenti a 14 vitigni dell'Alto Lazi
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Stili di vita e aspettative degli anziani. Risulttai di un'indagine nelle Università della Terza Età di Bari
No full textStili di vita e aspettative degli anziani. Un'indagine condotta nelle Università della Terza Età di Bar
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Wiggling and bending-free micron-sized solitons in periodically biased photorefractives
No full textConsidering nonlinear optical propagation through photorefractive crystals in which the bias voltage is periodically modulated along the propagation direction, we are able to identify the conditions in which a beam forms a soliton in a straight line down to micron-sized widths. The effect, which is numerically investigated considering the full (3+1) D spatio-temporal light-matter dynamics, emerges when the period of modulation of the bias is smaller than the beam diffraction length. In conditions in which the two scales are comparable, the soliton follows a characteristic wiggling trajectory, oscillating in response to the oscillating bias. The finding indicates a method to achieve highly miniaturized soliton-based photonic applications that do not require specific off-axis alignment. (C) 2008 Optical Society of America
Light-induced dielectric structures and enhanced self-focusing in critical photorefractive ferroelectrics
No full textWe consider the nonlinear dynamics occurring when an optical beam couples to dielectric material polarization in an unbiased photorefractive crystal undergoing a ferroelectric phase transition. The polarization profile produced by the light-induced electric field is evaluated by means of the Landau-Ginzburg approach and is found to manifest new thermodynamical states with their own specific nonlinear optical effects. We show that a temperature T(C), lower than the critical one, exists such that ( a) if T>T(C) the optical beam experiences an increasing self-focusing for decreasing temperatures and (b) if T>T(C) the optical beam allows the existence of thermodynamically metastable states associated with an optical ultra-self-focusing effect. (C) 2009 Optical Society of Americ
Collision and fusion of counterpropagating micrometer-sized optical beams in periodically biased photorefractive crystals
No full textWe theoretically investigate collision of optical beams traveling in opposite directions through a centrosymmetric photorefractive crystal biased by a spatially periodic voltage. We analytically predict the fusion of counterpropagating solitons in conditions in which the applied voltage is rapidly modulated along the propagation axis, so that self-bending is suppressed by the "restoring symmetry" mechanism. Moreover, when the applied voltage is slowly modulated, we predict that the modified self-bending allows conditions in which the two beams fuse together, forming a curved light-channel splice. (C) 2009 Optical Society of Americ
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