1,720,992 research outputs found
The parkin gene is not a major susceptibility locus for typical late-onset Parkinson's disease
No full textPhysical dispersion and disappearance of bacteria in the Golfo di Palermo: the results of two surveys.
Full text linkThis paper reports on some results of two surveys at sea carried out in the surroundings of a urban wastewater discharge on the coast of the Golfo di Palermo, western Sicily (Italy). At the time of the surveys (year 2005) the stretch of water lying before the central part of the capital town received the untreated wastewater originating from about 200 000 inhabitants, which was discharged on-shore without any prior treatment by the free-surface outfall of “Porta Felice main sewer”.
This outfall has crucial importance in the water quality; indeed, the Municipality is steadily implementing a plan featuring an intercepting main sewer along the coast and some pumping stations to connect all the main sewers to the main wastewater treatment plant, located in the SE boundary area of the town. At the moment of the surveys, however, no mitigation measure had been applied yet and the quality of the Gulf was still largely affected by it.
Part of the Sanitation Plan was the characterization of the seawater; to this aim, in August and November, 2005, the Università degli Studi di Palermo - on behalf of the Municipality’s Ufficio del Centro Storico - carried out two survey cruises in which the most important seawater quality features were investigated. What will be reported on herein is the part dealing with microbiological indicators, taking the salinity field as background
GENERAZIONE DI SECONDA ARMONICA RETRO-PROPAGANTE IN NIOBATO DI LITIO CON POLING PERIODICO
No full textWe report on backward second-harmonic-generation in bulk periodically poled congruent lithium niobate with a 3.2 micron period. A tunable continuous-wave Ti:Sapphire laser allowed us exciting two resonant quasi-phase-matched orders. Resonances were also resolved by temperature tuning
Random quasi-phase-matched second-harmonic generation in periodically poled lithium tantalate
No full textWe observe second harmonic generation via random quasi-phase-matching in a 2.0 micron periodically poled, 1-cm-long, z-cut lithium tantalate. Away from resonance, the harmonic output profiles exhibit a characteristic pattern stemming from a stochastic domain distribution and a quadratic growth with the fundamental excitation, as well as a broadband spectral response. The results are in good agreement with a simple model and numerical simulations in the undepleted regime, assuming an anisotropic spread of the random nonlinear component. (C) 2010 Optical Society of Americ
Features of randomized electric-field assisted domain inversion in lithium tantalate
Full text linkWe report on bulk and guided-wave second-harmonic generation via random Quasi-Phase-Matching in Lithium Tantalate. By acquiring the far-field profiles at several wavelengths, we extract statistical information on the distribution of the quadratic nonlinearity as well as its average period, both at the surface and in the bulk of the sample. By investigating the distribution in the two regions we demonstrate a non-invasive approach to the study of poling dynamics
Studio della Nonlinearità Quadratica di Zincoblende per la Generazione di TeraHertz in Guida d'Onda: un Confronto di Cristalli Differenti
No full textDFG TeraHertz generation can approach the quantum efficiency limit with much lower peak powers than bulk experiments. We give details on the model and on the waveguide geometry
Surface periodic poling in congruent lithium tantalate RID C-6421-2011
No full textThe first demonstration of surface periodic poling of lithium tantalate at high voltages is reported. Periodic domain inversion with mark-to-space ratios close to the optimum 50:50 was successfully achieved down to micrometre periods with good uniformity and repeatability
Ultraviolet quasi-phase-matched second harmonic generation in surface periodically poled lithium niobate optical waveguides
No full textThe compatibility of low concentration (alpha-phase) proton exchange channel waveguides with electric field surface periodic poling of congruent lithium niobate (SPPLN) crystals has been experimentally demonstrated. With such waveguides, we obtained ultraviolet second harmonic generation (SHG) by first order quasi-phase-matching (QPM), a result made possible by the fabrication, on Z-cut LN crystals, of periodic structures with a pitch down to 750 nm. Nonlinear copropagating QPM-SHG measurements have been carried out on such structures. The pump source was a Ti:sapphire laser with a tunability range of 700-980 nm and a 40 GHz linewidth. We have measured UV continuous wave light at 390 nm by means of a lock-in amplifier and a photodiode with an enhanced response in the UV. The measured conversion efficiency was about 1% W(-1) cm(-2)
- …
