Polychromatic Optical Bloch Oscillations

Bloch oscillations (BOs) of polychromatic beams in circularly-curved optical waveguide arrays are smeared out owing to the dependence of the BO spatial period on wavelength. Here it is shown that restoring of the self-imaging property of the array and approximate BOs over relatively broad spectral ranges can be achieved by insertion of suitable lumped phase slips uniformly applied across the array.Comment: 3 pages, 4 figure

Objective-free excitation of quantum emitters with a laser-written micro parabolic mirror

The efficient excitation of quantum sources such as quantum dots or single molecules requires high NA optics which is often a challenge in cryogenics, or in ultrafast optics. Here we propose a 3.2 um wide parabolic mirror, with a 0.8 um focal length, fabricated by direct laser writing on CdSe/CdS colloidal quantum dots, capable of focusing the excitation light to a sub-wavelength spot and to extract the generated emission by collimating it into a narrow beam. This mirror is fabricated via in-situ volumetric optical lithography, which can be aligned to individual emitters, and it can be easily adapted to other geometries beyond the paraboloid. This compact solid-state transducer from far-field to the emitter has important applications in objective-free quantum technologies

Nonlinear dielectric epsilon near-zero hybrid nanogap antennas

High-index Mie-resonant dielectric nanostructures provide a new framework to manipulate light at the nanoscale. In particular their local field confinement together with their inherently low losses at frequencies below their band-gap energy allows to efficiently boost and control linear and nonlinear optical processes. Here, we investigate nanoantennas composed of a thin indium-tin oxide layer in the center of a dielectric Gallium Phosphide nanodisk. While the linear response is similar to that of a pure GaP nanodisk, we show that the second and third-harmonic signals of the nanogap antenna are boosted at resonance. Linear and nonlinear finite-difference time-domain simulations show that the high refractive index contrast leads to strong field confinement inside the antenna's ITO layer. Measurement of ITO and GaP nonlinear susceptibilities deliver insight on how to engineer nonlinear nanogap antennas for higher efficiencies for future nanoscale devices.Comment: main: 18 pages, 4 figues, supplemental: 8 pages, 4 figures, 1 tabl

Molecular Profiling of Aggressive Lymphomas

In the last years, several studies of molecular profiling of aggressive lymphomas were performed. In particular, it was shown that DLBCL can be distinguished in two different entities according to GEP. Specifically, ABC and GCB subtypes were characterized by having different pathogenetic and clinical features. In addition, it was demonstrated that DLBCLs are distinct from BL. Indeed, the latter is a unique molecular entity. However, relevant pathological differences emerged among the clinical subtypes. More recently, microRNA profiling provided further information concerning BL-DLBCL distinction as well as for their subclassification. In this paper, the authors based on their own experience and the most updated literature review, the main concept on molecular profiling of aggressive lymphomas

A novel approach to the analysis of muscle synergies based on the average threshold crossing technique

The work herein presented aimed to investigate the application of the Average Threshold Crossing (ATC) technique in the analysis of muscle synergies. The ability of the technique to approximate different modulations of the electromyographic (EMG) data was assessed via simulations. By selecting the proper threshold and window length, it was possible to obtain R2 similarity values above 0.8. This result improved by averaging the ATC envelopes over multiple epochs. The technique was also tested on real EMG data collected from 8 subjects during over ground walking. The synergies extracted using the ATC technique showed high similarity with the ones obtained with a standard approach using the EMG envelopes for both weights and temporal activations

AI: profili etici. Una prospettiva etica sull'Intelligenza Artificiale: princ\uecpi, diritti e raccomandazioni

As technologies become more and more pervasive in our everyday life new questions arise, for example, about security, accountability, fairness and ethics. These concerns are about all the realities that are involved or committed in designing, implementing, deploying and using the technology. This document addresses such concerns by presenting a set of practical obligations and recommendations for the development of applications and systems based on Artificial Intelligence (AI) techniques. These are derived from a definition of rights resulting from principles and ethical values rooted in the foundational charters of our social organization

Transparent control in overground walking exoskeleton reveals interesting changing in subject's stepping frequency

ABSTRACT: Lower-limb gait training (GT) exoskeletons have been successfully used in rehabilitation programs to overcome the burden of locomotor impairment. However, providing suitable net interaction torques to assist patient movements is still a challenge. Previous transparent operation approaches have been tested in treadmill-based GT exoskeletons to improve user-robot interaction. However, it is not yet clear how a transparent lower-limb GT system affects user’s gait kinematics during overground walking, which unlike treadmill-based systems, requires active participation of the subjects to maintain stability. In this study, we implemented a transparent operation strategy on the ExoRoboWalker, an overground GT exoskeleton, to investigate its effect on the user’s gait. The approach employs a feedback zero-torque controller with feedforward compensation for the exoskeleton’s dynamics and actuators’ impedance. We analyzed the data of five healthy subjects walking overground with the exoskeleton in transparent mode (ExoTransp) and non-transparent mode (ExoOff) and walking without exoskeleton (NoExo). The transparent controller reduced the user-robot interaction torque and improved the user’s gait kinematics relative to ExoOff. No significant difference in stride length is observed between ExoTransp and NoExo (p = 0.129). However, the subjects showed a significant difference in cadence between ExoTransp (50.9± 1.1 steps/min) and NoExo (93.7 ± 8.7 steps/min) (p = 0.015), but not between ExoTransp and ExoOff (p = 0.644). Results suggest that subjects wearing the exoskeleton adjust their gait as in an attention-demanding task changing the spatiotemporal gait characteristics likely to improve gait balance

Electrical control of single-photon emission in highly charged individual colloidal quantum dots

Electron transfer to an individual quantum dot promotes the formation of charged excitons with enhanced recombination pathways and reduced lifetimes. Excitons with only one or two extra charges have been observed and exploited for very efficient lasing or single-quantum dot light-emitting diodes. Here, by room-temperature time-resolved experiments on individual giant-shell CdSe/CdS quantum dots, we show the electrochemical formation of highly charged excitons containing more than 12 electrons and 1 hole. We report the control over intensity blinking, along with a deterministic manipulation of quantum dot photodynamics, with an observed 210-fold increase in the decay rate, accompanied by 12-fold decrease in the emission intensity, while preserving single-photon emission characteristics. These results pave the way for deterministic control over the charge state, and room-temperature decay rate engineering for colloidal quantum dot-based classical and quantum communication technologies

Second harmonic generation at a time-varying interface

Time-varying metamaterials rely on large and fast changes of the linear permittivity. Beyond the linear terms, however, the effect of a non-perturbative modulation of the medium on harmonic generation and the associated nonlinear susceptibilities remains largely unexplored. In this work, we study second harmonic generation at an optically pumped time-varying interface between air and a 310 nm Indium Tin Oxide film. We observe an enhancement of the modulation contrast at the second harmonic wavelength, up to 93% for a pump intensity of 100 GW/cm$^2$, leading to large frequency broadening and shift. We demonstrate that, in addition to the quadratic dependence on the fundamental field, a significant contribution to the enhancement comes from the temporal modulation of the second order nonlinear susceptibility, whose relative change is double that of the linear term. Moreover, the spectra resulting from single and double-slit time diffraction show significantly enhanced frequency shift, broadening and modulation depth, when compared to the infrared fundamental beam, and could be exploited for optical computing and sensing. Enhanced time-varying effects on the harmonic signal extends the application of materials to the visible range and calls for further theoretical exploration of non-perturbative nonlinear optics.Comment: 19 pages, 3 figures, 8 supplementary figure

CommonS e CommonSpaces: per una applicazione dei principi CommonS ad un MetaWeb del Digital Heritage italiano

Il termine “commons” è al centro nell’ultimo trentennio di ricerche dal punto di vista economico, tecnologico e sociale, ben sintetizzate da J.Rifkin che sviluppa le teorie che hanno fruttato il Nobel per l’economia ad E. Ostrom. La teoria dei beni comuni (commons) preconizza l’avvento di una società in cui prevale il diritto all’accesso rispetto al diritto di proprietà. Osserviamo questo cambiamento nelle strategie di protagonisti dell’economia mondiale. È singolare tuttavia notare come gli sviluppi di questa fase di transizione abbiano dato forza a giganteschi gruppi sovranazionali (Google, Facebook, LinkedIn ..) il cui capitale è alimentato dalla partecipazione di un pubblico planetario “allo stesso pasto”. Il capitale di questi giganti dell’era digitale è il contenuto fornito dagli utenti e l’insieme degli algoritmi che gestiscono lo scambio regolato di informazione tra miliardi di persone. Come dovrebbero intelligentemente reagire i responsabili delle collezioni digitali (“digital heritage”) e le istituzioni che sopraintendono alla valorizzazione dei beni culturali in Italia? Quale lezione dovrebbero imparare dalla evoluzione delle compagnie private che sui contenuti generati dagli utenti hanno fondato i propri imperi? Il nostro suggerimento è quello di creare una stretta relazione tra responsabili dei contenuti e responsabili dei prosumers dei beni culturali, identificati in primo luogo con studenti e docenti di secondarie e università; e di creare un circuito virtuoso di valorizzazione basato sui dati dell’esperienza con il Digital Heritage, creando, mediante protocolli che si vanno affermando di recente (xAPI,OpenBadge), un MetaWeb dei Beni Culturali che serva da un lato le istituzioni educative per certificare le attività di apprendimento svolte dagli apprendenti, e dall’altro i responsabili del Web Culturale fornendo loro informazioni di profilazione assai più dettagliate che in passato