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Romano P. | Romano R. | Romano J. D. | Romano Antonio Enea | Romano D. | Romano Joseph D. | Romano Donatella | Romano Raffaele | Romano Flavio | Romano A.

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Low-defectiveness exfoliation of MoS2 nanoparticles and their embedment in hybrid light-emitting polymer nanofibers

Portone Alberto, Romano Luigi, Fasano Vito, Di Corato Riccardo, Camposeo Andrea, Fabbri Filippo, Cardarelli Francesco, Pisignano Dario, Persano Luana
17 Nov 2018 cond-mat.mtrl-sci arxiv.org/abs/1811.07217

Molybdenum disulfide (MoS2) has been attracting extraordinary attention for its intriguing optical, electronic and mechanical properties. Here we demonstrate hybrid, organic-inorganic light-emitting nanofibers based on MoS2 nanoparticle dopants obtained through a simple and inexpensive sonication process in N-methyl-2-pyrrolidone and successfully encapsulated in polymer filaments. Defectiveness is found to be kept low, and stoichiometry preserved, by the implemented, gentle exfoliation method that allows the MoS2 nanoparticles to be produced. So-achieved hybrid fibers are smooth, uniform, flawless, and exhibit bright and continuous light emission. Moreover, they show significant capability of waveguiding self-emitted light along their longitudinal axis. These findings suggest the use of emissive MoS2 fibers enabled by gentle exfoliation methods as novel and highly promising optical material for building sensing surfaces and as components of photonic circuits.

Stacked electrospun polymer nanofiber heterostructures with tailored stimulated emission

Sznitko Lech, Romano Luigi, Wawrzynczyk Dominika, Cyprych Konrad, Mysliwiec Jaroslaw, Pisignano Dario
03 Jul 2018 cond-mat.mtrl-sci arxiv.org/abs/1807.01288

We present stacked organic lasing heterostructures made by different species of light-emitting electrospun fibers, each able to provide optical gain in a specific spectral region. A hierarchical architecture is obtained by conformable layers of fibers with disordered two-dimensional organization and three-dimensional compositional heterogeneity. Lasing polymer fibers are superimposed in layers, showing asymmetric optical behavior from the two sides of the organic heterostructure, and tailored and bichromatic stimulated emission depending on the excitation direction. A marginal role of energy acceptor molecules in determining quenching of high-energy donor species is evidenced by luminescence decay time measurements. These findings show that non-woven stacks of light-emitting electrospun fibers doped with different dyes exhibit critically-suppressed F\"orster resonance energy transfer, limited at joints between different fiber species. This leads to obtain hybrid materials with mostly physically-separated acceptors and donors, thus largely preventing donor quenching and making much easier to achieve simultaneous lasing from multiple spectral bands. Coherent backscattering experiments are also performed on the system, suggesting the onset of random lasing features. These new organic lasing systems might find application in microfluidic devices where flexible and bidirectional excitation sources are needed, optical sensors, and nanophotonics.

Interplay of Stimulated Emission and Fluorescence Resonance Energy Transfer in Electrospun Light-Emitting Fibers

Sznitko Lech, Romano Luigi, Camposeo Andrea, Wawrzynczyk Dominika, Cyprych Konrad, Mysliwiec Jaroslaw, Pisignano Dario
28 Dec 2017 cond-mat.mtrl-sci arxiv.org/abs/1712.09784

Concomitant amplified spontaneous emission (ASE) and F\"orster resonance energy transfer (FRET) are investigated in electrospun light-emitting fibers. Upon dye-doping with a proper FRET couple system, free-standing fibrous mats exhibit tunable FRET efficiency and, more importantly, tailorable threshold conditions for stimulated emission. In addition, effective scattering of light is found in the fibrous material by measuring the transport mean free path of photons by coherent backscattering experiments. The interplay of ASE and FRET leads to high control in designing optical properties from electrospun fibers, including the occurrence of simultaneous stimulated emission from both donor and acceptor components. All tunable-optical properties are highly interesting in view of applying electrospun light-emitting materials in lightening, display, and sensing technologies.

Big Data Analytics for QoS Prediction Through Probabilistic Model Checking

Cicotti Giuseppe, Coppolino Luigi, D'Antonio Salvatore, Romano Luigi
01 May 2014 cs.SE arxiv.org/abs/1405.0327

As competitiveness increases, being able to guaranting QoS of delivered services is key for business success. It is thus of paramount importance the ability to continuously monitor the workflow providing a service and to timely recognize breaches in the agreed QoS level. The ideal condition would be the possibility to anticipate, thus predict, a breach and operate to avoid it, or at least to mitigate its effects. In this paper we propose a model checking based approach to predict QoS of a formally described process. The continous model checking is enabled by the usage of a parametrized model of the monitored system, where the actual value of parameters is continuously evaluated and updated by means of big data tools. The paper also describes a prototype implementation of the approach and shows its usage in a case study.

A Hierarchical Approach for Dependability Analysis of a Commercial Cache-Based RAID Storage Architecture

Kaaniche Mohamed, Romano Luigi, Kalbarczyk Zbigniew, Iyer Ravishankar, Karcich Rick
06 Apr 2007 cs.PF arxiv.org/abs/0704.0879

We present a hierarchical simulation approach for the dependability analysis and evaluation of a highly available commercial cache-based RAID storage system. The archi-tecture is complex and includes several layers of overlap-ping error detection and recovery mechanisms. Three ab-straction levels have been developed to model the cache architecture, cache operations, and error detection and recovery mechanism. The impact of faults and errors oc-curring in the cache and in the disks is analyzed at each level of the hierarchy. A simulation submodel is associated with each abstraction level. The models have been devel-oped using DEPEND, a simulation-based environment for system-level dependability analysis, which provides facili-ties to inject faults into a functional behavior model, to simulate error detection and recovery mechanisms, and to evaluate quantitative measures. Several fault models are defined for each submodel to simulate cache component failures, disk failures, transmission errors, and data errors in the cache memory and in the disks. Some of the parame-ters characterizing fault injection in a given submodel cor-respond to probabilities evaluated from the simulation of the lower-level submodel. Based on the proposed method-ology, we evaluate and analyze 1) the system behavior un-der a real workload and high error rate (focusing on error bursts), 2) the coverage of the error detection mechanisms implemented in the system and the error latency distribu-tions, and 3) the accumulation of errors in the cache and in the disks.

On the Constraint Algebra of Degenerate Relativity

Romano Joseph D.
28 Jun 1993 gr-qc arxiv.org/abs/gr-qc/9306034

As shown by Ashtekar in the mid 80's, general relativity can be extended to incorporate degenerate metrics. This extension is not unique, however, as one can change the form of the hamiltonian constraints and obtain an {\it alternative} degenerate extension of general relativity that disagrees with Ashtekar's original theory when the triads vectors are degenerate. In this paper, the constraint algebra of a particular alternative theory is explicitly evaluated and compared with that of Ashtekar's original degenerate extension. A generic classification of the difference between the two theories is given in terms of the degeneracy and surface-forming properties of the triad vectors. (This classification is valid when the degeneracy and surface-forming properties of the triad vectors is the same everywhere in an open set about a point in space.) If the triad vectors are degenerate and surface-forming, then all the secondary constraints of the alternative degenerate extension are satisfied as a consequence of the primary constraints, and the constraints of this theory are weaker than those of Ashtekar's. If the degenerate triad vectors are not surface-forming, then the first secondary constraint of the alternative theory already implies equivalence with Ashtekar's degenerate extension. What happens when the degeneracy and surface-forming properties of the triad vectors change from point to point is an open question.

Nematogenic Lattice Models in One or Two Dimensions and with Long-Range Interactions

Angelescu N., Romano S., Zagrebnov V. A.
09 May 1994 cond-mat arxiv.org/abs/cond-mat/9405020

Extending previous rigorous results, we prove existence of an ordering transition at finite temperature for a class of nematogenic lattice models, where spins are associated with a one- or two-dimensional lattice, and interact via long-range potentials.

Nonclassical Light in Interferometric Measurements

Ansari N. A., Di Fiore L., Man'ko M. A., Man'ko V. I., Romano R., Solimeno S., Zaccaria F.
26 Jul 1994 hep-th arxiv.org/abs/hep-th/9407171

It is shown that the even and odd coherent light and other nonclassical states of light like superposition of coherent states with different phases may replace the squeezed light in interferometric gravitational wave detector to increase its sensitivity. (Contribution to the Second Workshop on Harmonic Oscillator, Cocoyoc, Mexico, March 1994)

Embedding initial data for black hole collisions

Romano Joseph D., Price Richard H.
21 Sep 1994 gr-qc arxiv.org/abs/gr-qc/9409047

We discuss isometric embedding diagrams for the visualization of initial data for the problem of the head-on collision of two black holes. The problem of constructing the embedding diagrams is explicitly presented for the best studied initial data, the Misner geometry. We present a partial solution of the embedding diagrams and discuss issues related to completing the solution.

On Long-Range Order in Low-Dimensional Lattice-Gas Models of Nematic Liquid Crystals

Angelescu N., Romano S., Zagrebnov V. A.
08 Nov 1994 cond-mat arxiv.org/abs/cond-mat/9411033

The problem of the orientational ordering transition for lattice-gas models of liquid crystals is discussed in the low-dimensional case $d=1,2$. For isotropic short-range interactions, orientational long-range order at finite temperature is excluded for any packing of molecules on the lattice $Z^d$; on the other hand, for reflection-positive long-range isotropic interactions, we prove existence of an orientational ordering transition for high packing ($\mu

\mu_0$) and low temperatures ($\beta > \beta_c(\mu)$).