Results for "Armanda Ottaviano Quintavalle"

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Two-tier blockchain timestamped notarization with incremental securityFeb 08 2019Digital notarization is one of the most promising services offered by modern blockchain-based solutions. We present a digital notary design with incremental security and cost reduced with respect to current solutions. A client of the service receives ... More
Fast Compressed Tries through Path DecompositionsNov 22 2011Dec 03 2011Tries are popular data structures for storing a set of strings, where common prefixes are represented by common root-to-node paths. Over fifty years of usage have produced many variants and implementations to overcome some of their limitations. We explore ... More
Dimensional dependence of naked singularity formation in spherical gravitational collapseJul 11 2007Jun 05 2008The complete spectrum of the endstates - naked singularities, or blackholes - of gravitational collapse is analyzed for a wide class of $N$-dimensional spacetimes in spherical symmetry, which includes and generalizes the dust solutions and the case of ... More
Epidemics on networks with heterogeneous population and stochastic infection ratesFeb 03 2016Jul 21 2016In this paper we study the diffusion of an SIS-type epidemics on a network under the presence of a random environment, that enters in the definition of the infection rates of the nodes. Accordingly, we model the infection rates in the form of independent ... More
The Wavelet Trie: Maintaining an Indexed Sequence of Strings in Compressed SpaceApr 16 2012An indexed sequence of strings is a data structure for storing a string sequence that supports random access, searching, range counting and analytics operations, both for exact matches and prefix search. String sequences lie at the core of column-oriented ... More
Fast Scalable Construction of (Minimal Perfect Hash) FunctionsMar 14 2016Mar 22 2016Recent advances in random linear systems on finite fields have paved the way for the construction of constant-time data structures representing static functions and minimal perfect hash functions using less space with respect to existing techniques. The ... More
A Comparison of Maps Application Programming InterfacesMay 15 2013The development of web applications that manipulate geo-referenced information is often supported by Application Programming Interfaces (APIs), al-lowing a fast development cycle for high quality applications. APIs can be used by programmers with different ... More
Epidemic Outbreaks in Networks with Equitable or Almost-Equitable PartitionsDec 12 2014Nov 13 2015We study the diffusion of epidemics on networks that are partitioned into local communities. The gross structure of hierarchical networks of this kind can be described by a quotient graph. The rationale of this approach is that individuals infect those ... More
UV-photoelectric effect for augmented contrast and resolution in electron microscopyApr 04 2016A new tool providing material contrast control in scanning electron microscopy (SEM) is demonstrated. The approach is based on deep-UV illumination during SEM imaging and delivers a novel material based contrast as well as higher resolution due to the ... More
Dilaton Interactions and the Anomalous Breaking of Scale Invariance of the Standard ModelJun 04 2012Apr 24 2013We discuss the main features of dilaton interactions for fundamental and effective dilaton fields. In particular, we elaborate on the various ways in which dilatons can couple to the Standard Model and on the role played by the conformal anomaly as a ... More
Kirchhoff's metasurfacesMay 12 2018Thermo-optical properties of the nanodisc and metal hole array plasmonic perfect absorber (PPA) metasurfaces were designed and characterised at midinfrared wavelengths. Both, light emitter and detector systems are highly thought after for the future sensor ... More
Fiber Bragg Grating Based ThermometryMar 24 2016In recent years there has been considerable interest in developing photonic temperature sensors such as the Fiber Bragg gratings (FBG) as an alternative to resistance thermometry. In this study we examine the thermal response of FBGs over the temperature ... More
Multipurpose High Frequency Electron Spin Resonance Spectrometer for Condensed Matter ResearchOct 29 2009We describe a quasi-optical multifrequency ESR spectrometer operating in the 75-225 GHz range and optimized at 210 GHz for general use in condensed matter physics, chemistry and biology. The quasi-optical bridge detects the change of mm wave polarization ... More
Heterogeneous SIS model for directed networks and optimal curing policyFeb 15 2016Jul 21 2016We investigate the influence of the contact network structure on the spread of epidemics over an heterogeneous population. In our model, the epidemic process spreads over a directed weighted graph. A continuous-time individual-based susceptible-infected-susceptible ... More
Cache-Oblivious Peeling of Random HypergraphsDec 02 2013The computation of a peeling order in a randomly generated hypergraph is the most time-consuming step in a number of constructions, such as perfect hashing schemes, random $r$-SAT solvers, error-correcting codes, and approximate set encodings. While there ... More
AlGaAs-On-Insulator Nonlinear PhotonicsSep 11 2015The combination of nonlinear and integrated photonics has recently seen a surge with Kerr frequency comb generation in micro-resonators as the most significant achievement. Efficient nonlinear photonic chips have myriad applications including high speed ... More
Micro-thermocouple on nano-membrane: thermometer for nanoscale measurementsApr 08 2018A thermocouple of Au-Ni with only 2.5-micrometers-wide electrodes on a 30-nm-thick Si3N4 membrane was fabricated by a simple low-resolution electron beam lithography and lift off procedure. The thermocouple is shown to be sensitive to heat generated by ... More
Au-Ag-Cu nano-alloys: tailoring of permittivityApr 11 2016Precious metal alloys enables new possibilities to tailor materials for specific optical functions. Here we present a systematic study of the effects of a nanoscale alloying on the permittivity of Au-Ag-Cu metals at 38 different atomic mixing ratios. ... More
Mg5C60: A stable two dimensional conducting polymerJan 25 2008We present a study on the structural, spectroscopic, conducting and magnetic properties of Mg5C60, a two dimensional (2D) fulleride polymer. The polymer phase is stable up to the exceptionally high temperature of 823 K. Infrared and Raman studies suggest ... More
Developing Microwave Photonic Temperature SensorsAug 06 2015In recent years there has been considerable interest in exploiting the temperature dependence of sapphire whispering gallery mode frequency to develop a mechanically stable, high accuracy temperature sensor. Disk-resonator-based devices have been demonstrated ... More
Enhanced thermal stability and spin-lattice relaxation rate of N@C60 inside carbon nanotubesJan 30 2008We studied the temperature stability of the endohedral fullerene molecule, N@C60, inside single-wall carbon nanotubes using electron spin resonance spectroscopy. We found that the nitrogen escapes at higher temperatures in the encapsulated material as ... More
Mechanism of formation of a 2D binary alloyMar 27 2001Direct comparison of scanning tunneling microscopy and high resolution core level photo-emission experiments provides a rationale for the mechanism of formation of a two dimensional (2D) binary alloy (1/3 mono-layer (ML) Sn(1- x)Six/Si(111)-\sqrt3X\sqrt3R30). ... More
Threshold Characteristics of Slow-Light Photonic Crystal LasersAug 21 2015The threshold properties of photonic crystal quantum dot lasers operating in the slow-light regime are investigated experimentally and theoretically. Measurements show that, in contrast to conventional lasers, the threshold gain attains a minimum value ... More
Magneto-optical characterization of MnxGe1-x alloys obtained by ion implantationSep 08 2006Magneto-optical Kerr effect hysteresis loops at various wavelengths in the visible/near-infrared range have been used to characterize the magnetic properties of alloys obtained by implanting Mn ions at fixed energy in a Ge matrix. The details of the hysteresis ... More
Tunable MEMS VCSEL on Silicon substrateMar 20 2019We present design, fabrication and characterization of a MEMS VCSEL which utilizes a silicon-on-insulator wafer for the microelectromechanical system and encapsulates the MEMS by direct InP wafer bonding, which improves the protection and control of the ... More
Learning the undecidable from networked systemsApr 08 2019This article presents a theoretical investigation of computation beyond the Turing barrier from emergent behavior in distributed (or parallel) systems. In particular, we present an algorithmic network that is a mathematical model of a networked population ... More
Magnetization driven metal - insulator transition in strongly disordered Ge:Mn magnetic semiconductorsMar 31 2009We report on the temperature and field driven metal-insulator transition in disordered Ge:Mn magnetic semiconductors accompanied by magnetic ordering, magnetoresistance reaching thousands of percents and suppression of the extraordinary Hall effect by ... More
Role of substrate on interaction of water molecules with graphene oxide and reduced graphene oxideApr 26 2018We study local electronic properties of graphene oxide (GO) and reduced graphene oxide (RGO) on metallic (Pt) and insulating (Si3N4) substrates in controlled humidity environment. We demonstrate that the supporting substrate plays a crucial role in interaction ... More
Compressing Graphs and Indexes with Recursive Graph BisectionFeb 29 2016Graph reordering is a powerful technique to increase the locality of the representations of graphs, which can be helpful in several applications. We study how the technique can be used to improve compression of graphs and inverted indexes. We extend the ... More
Formation of extended thermal etch pits on annealed Ge wafersSep 10 2018An extended formation of faceted pit-like defects on Ge(001) and Ge(111) wafers was obtained by thermal cycles to T> 750 {\deg}C. This temperature range is relevant in many surface-preparation recipes of the Ge surface. The density of the defects depends ... More
Phase segregation on the nanoscale in Na2C60Jul 10 2006Oct 15 2006Na2C60 is believed to be an electron-hole counterpart of the Mott-Jahn--Teller insulator A4C60 salts. We present a study of infrared, ESR, NMR spectroscopy, X-ray diffraction, chemical composition and neutron scattering on this compound. Our spectroscopic ... More
Paracetamol Micro-Structure Analysis by Optical MappingDec 24 2018Domain structure of paracetamol -- popular antipyretic analgesic -- was investigated by infrared (IR) spectroscopy using synchrotron radiation. Absorbance and retardance maps reveal molecular orientation inside the micro-domains of the paracetamol form ... More
Percolation threshold gold films on columnar coatings: characterisation for SERS applicationsMar 27 2016Percolation of gold films of ~15 nm thickness was controlled to achieve the largest openings during Au deposition. Gold was evaporated on 300-nm-thick films of nanostructured porous and columnar SiO2, TiO2 and MgF2 which were deposited by controlling ... More
Electronic and ionic conductivities in superionic Li$_4$C$_{60}$Mar 04 2016The $10$ GHz microwave conductivity, $\sigma(T)$ and high field, $222$ GHz electron spin resonance (HF-ESR) of Li$_4$C$_{60}$ fulleride is measured in a wide temperature range. We suggest that the majority of ESR active sites and at least some of the ... More
Islanding, growth mode and ordering in Si heteroepitaxy on Ge(001) substrates structured by thermal annealingFeb 04 2019Si/Ge heteroepitaxial dots under tensile strain are grown on nanostructured Ge substrates produced by high-temperature flash heating exploiting the spontaneous faceting of the Ge(001) surface close to the onset of surface melting. A very diverse growth ... More
Orientational Mapping Augmented Sub-Wavelength Hyper-Spectral Imaging of SilkJun 05 2017Molecular alignment underpins optical, mechanical, and thermal properties of materials, however, its direct measurement from volumes with micrometer dimensions is not accessible, especially, for structurally complex bio-materials. How the molecular alignment ... More
Photoacoustic signal enhancements from gold nano-colloidal suspensions excited by a pair of time-delayed femtosecond pulsesJul 25 2017Photoacoustic signal enhancements were observed with a pair of time-delayed femtosecond pulses upon excitation of gold nanosphere colloidal suspension. A systematic experimental investigation of photoacoustic intensity within the delay time, t = 0 to ... More
Nanoscale chemical mapping of laser-solubilized silkAug 25 2017A water soluble amorphous form of silk was made by ultra-short laser pulse irradiation and detected by nanoscale IR mapping. An optical absorption-induced nanoscale surface expansion was probed to yield the spectral response of silk at IR molecular fingerprinting ... More
Efficient X-ray generation from gold colloidal solutionsApr 26 2016Hard X-ray generation for Au nanoparticle dispersion was systematically investigated for different particle diameters ranging from 10 to 100 nm with a narrow size distribution of +/- 2%. Scaling law of X-ray generation is close to a 6-photon process before ... More
Trapping ultracold atoms at 100 nm from a chip surface in a 0.7-micrometer-period magnetic latticeMay 26 2017Aug 09 2017We report the trapping of ultracold 87Rb atoms in a 0.7 micron-period 2D triangular magnetic lattice on an atom chip. The magnetic lattice is created by a lithographically patterned magnetic Co/Pd multilayer film plus bias fields. Rubidium atoms in the ... More
Optical readout of hydrogen storage in films of Au and PdJun 17 2017For hydrogen sensor and storage applications, films of Au and Pd were (i) co-sputtered at different rates or (ii) deposited in a sequential layer-by-layer fashion on a cover glass. Peculiarities of hydrogen uptake and release were optically monitored ... More
Polarisation of THz synchrotron radiation: from its measurement to controlJul 01 2017Polarisation analysis of synchrotron THz radiation was carried out with a standard stretched polyethylene polariser and revealed that the linearly polarised (horizontal) component contributes up to 22 +/- 5% to the circular polarised synchrotron emission ... More
Nanoscale optical and structural characterisation of silkFeb 07 2019Background: Nanoscale composition of silk defining its unique properties via a hierarchical structural anisotropy has to be analysed at the highest spatial resolution of tens-of-nanometers corresponding to the size of fibrils made of b-sheets, which are ... More
The Conformal Anomaly and the Neutral Currents Sector of the Standard ModelJan 08 2011Apr 26 2011We elaborate on the structure of the graviton-gauge-gauge vertex in the electroweak theory, obtained by the insertion of the complete energy-momentum tensor ($T$) on 2-point functions of neutral gauge currents ($VV'$). The vertex defines the leading contribution ... More