Optimal frequency conversion in the nonlinear stage of modulation instability

We investigate multi-wave mixing associated with the strongly pump depleted regime of induced modulation instability (MI) in optical fibers. For a complete transfer of pump power into the sideband modes, we theoretically and experimentally demonstrate that it is necessary to use a much lower seeding modulation frequency than the peak MI gain value. Our analysis shows that a record 95 % of the input pump power is frequency converted into the comb of sidebands, in good quantitative agreement with analytical predictions based on the simplest exact breather solution of the nonlinear Schr\"odinger equation

Phytochemical and biological characterization of dry outer scales extract from Tropea red onion (Allium cepa L. var. Tropea)–A promising inhibitor of pancreatic lipase

Background: Allium cepa L. var. Tropea is typically cultivated in Calabria (Italy) and it is certified as “Cipolla Rossa di Tropea Calabria-PGI” (Tropea red onion). The use of clinically available anti-obesity drugs such as Orlistat is being gradually dismissed due to their side-effects and this has encouraged the search for alternative inhibitors of intestinal lipases such as phytochemicals showing less side-effects. In this study we aimed to evaluate for the first time the anti-obesity potential of the hydroalcoholic extract from the dry outer scales of Tropea red onion by the assesment of its capacity to inhibit pancreatic lipase. Its possible mechanism of action was also studied with planar lipid membranes (PLMs) surrogate of intestinal membranes. Methods: Specialized metabolites in the extract were determined by GC–MS, HPLC-DAD, HPLC-UV-DAD and HPLC-HRMS analyses. Inhibition of pancreatic lipase was studied in vitro against crude lipase Type II from porcine pancreas. PLMs used in the electrophysiology measurements were made up of DOPS:DOPE:POPC. Results: The extract contained quercetin-4′-O-glucoside, quercetin and quercetin-3,4′-O-diglucoside as the most abundant phenolics. Among apolar constituents, γ-sitosterol, linoleic and stearic acids were dominant. The lipase inhibitory effect of the extract had an IC50 value equal to 0.77±0.03 mg/mL (positive control, IC50 = 0.018 mg/mL). The electrophysiological study demonstrated that the extract is able to incorporate into PLMs and to form transient channel-like events Conclusions: Taken altogether, the results allow us to suggest that the hydroalcoholic extract from the dry outer scales of Tropea red onion could prevent lipid ester hydrolysis and it has a protective effect against phospholipase as found for interfacially active compounds

Polarization modulation instability in a Manakov fiber system

The Manakov model is the simplest multicomponent model of nonlinear wave theory: It describes elementary stable soliton propagation and multisoliton solutions, and it applies to nonlinear optics, hydrodynamics, and Bose-Einstein condensates. It is also of fundamental interest as an asymptotic model in the context of the widely used wavelength-division-multiplexed optical fiber transmission systems. However, although its physical relevance was confirmed by the experimental observation of Manakov (vector) solitons in a planar waveguide in 1996, there have in fact been no quantitative experiments confirming its validity for nonlinear dynamics other than soliton formation. Here, we report experiments in optical fiber that provide evidence of passband and baseband polarization modulation instabilities in a defocusing Manakov system. In the spontaneous regime, we also reveal a unique saturation effect as the pump power increases. We anticipate that such observations may impact the application of this minimal model to describe and understand more complicated phenomena in nature, such as the formation of extreme waves in multicomponent systems

The Agile Alert System For Gamma-Ray Transients

In recent years, a new generation of space missions offered great opportunities of discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) onboard the AGILE space mission. The AGILE-GRID, sensitive in the energy range of 30 MeV-30 GeV, has detected many gamma-ray transients of galactic and extragalactic origins. This work presents the AGILE innovative approach to fast gamma-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe: (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for gamma-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, e-mails, and push notifications of an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in gamma-ray astrophysics.Comment: 34 pages, 9 figures, 5 table

Graphical Encoding of a Spatial Logic for the pi-Calculus

This paper extends our graph-based approach to the verification of spatial properties of π-calculus specifications. The mechanism is based on an encoding for mobile calculi where each process is mapped into a graph (with interfaces) such that the denotation is fully abstract with respect to the usual structural congruence, i.e., two processes are equivalent exactly when the corresponding encodings yield isomorphic graphs. Behavioral and structural properties of π-calculus processes expressed in a spatial logic can then be verified on the graphical encoding of a process rather than on its textual representation. In this paper we introduce a modal logic for graphs and define a translation of spatial formulae such that a process verifies a spatial formula exactly when its graphical representation verifies the translated modal graph formula