Super-resolution with Toraldo pupils: analysis with electromagnetic numerical simulations

The concept of super-resolution refers to various methods for improving the angular resolution of an optical imaging system beyond the classical diffraction limit. In optical microscopy, several techniques have been developed with the aim of narrowing the central lobe of the illumination Point Spread Function (PSF). In Astronomy a few methods have been proposed to achieve reflector telescopes and antennas with resolution significantly better than the diffraction limit but, to our best knowledge, no working system is in operation. A possible practical approach consists of using the so-called "Toraldo Pupils" (TPs) or variable transmittance filters. These pupils were introduced by G. Toraldo di Francia in 1952,1 and consist of a series of discrete, concentric circular coronae providing specific optical transparency and dephasing in order to engineer the required PSF. The first successful laboratory test of TPs in the microwaves was achieved in 2003,2 and in the present work we build upon these initial measurements to perform electromagnetic (EM) numerical simulations of TPs, using a commercial full-wave software tool. These simulations were used to study various EM effects that can mask and/or affect the performance of the pupils and to analyze the near-field as well as the far-field response. Our EM analysis confirms that at 20 GHz the width of the central lobe in the far-field generated by a TP significantly decreases compared to a clear circular aperture with the same diameter

Laboratory measurements of super-resolving Toraldo pupils for radio astronomical applications

The concept of super-resolution refers to various methods for improving the angular resolution of an optical imaging system beyond the classical diffraction limit. Although several techniques to narrow the central lobe of the illumination Point Spread Function have been developed in optical microscopy, most of these methods cannot be implemented on astronomical telescopes. A possible exception is represented by the variable transmittance filters, also known as "Toraldo Pupils" (TPs) since they were introduced for the first time by G. Toraldo di Francia in 1952 (Toraldo di Francia, Il Nuovo Cimento (Suppl.) 9, 426, 1952). In the microwave range, the first successful laboratory test of TPs was performed in 2003 (Mugnai et al. Phys. Lett. A 311, 77-81, 2003). These first results suggested that TPs could represent a viable approach to achieve super-resolution in Radio Astronomy. We have therefore started a project devoted to a more exhaustive analysis of TPs, in order to assess their potential usefulness to achieve super-resolution on a radio telescope, as well as to determine their drawbacks. In the present work we report on the results of extensive microwave measurements, using TPs with different geometrical shapes, which confirm the correctness of the first experiments in 2003. We have also extended the original investigation to carry out full-wave electromagnetic numerical simulations and also to perform planar scanning of the near-field and transform the results into the far-field

Design of Super-Resolving Toraldo Pupils for Radio Astronomical Applications

More than half a century ago, in 1952, Giuliano Toraldo di Francia suggested that the resolving power of an optical instrument could be improved using a filter consisting of finite-width concentric coronae of different amplitude and phase transmittance, now known as Toraldo Pupils (TPs). The concept of “super-resolution” was born, and in the cur- rent literature it is generally associated with various meth- ods for improving the angular resolution of an optical imag- ing system beyond the classical diffraction limit. In the mi- crowave range, the first successful laboratory test of TPs was performed in 2003. These first results suggested that TPs could represent a viable approach to achieve super- resolution in Radio Astronomy. We have therefore started a project devoted to an exhaustive study of TPs and how they could be implemented on a radio telescope. In this work we present a summary of the status of this project, and then we describe a preliminary design to implement a TP system on a 32-m radio telescope

Foscolo critico

Il volume, primo della collana open access dei "Quaderni di Gargnano", ospita i contributi presentati al XV Convegno internazionale di Letteratura italiana "Gennaro Barbarisi", tenutosi a Gargnano del Garda dal 24 al 26 settembre 2012. Il "Quaderno", dedicato al Foscolo critico, accoglie contributi di Giovanni Biancardi, Arnaldo Bruni, Andrea Campana, Massimo Castellozzi, Gustavo Costa, Alfredo Cottignoli, Christian Del Vento, Sandro Gentili, Franco Longoni, Ilaria Mangiavacchi, Donatella Martinelli, Giuseppe Natale, Enzo Neppi, Matteo Palumbo, Elena Parrini Cantini, Chiara Piola Caselli. \uc8 aperto da una Prefazione di Claudia Berra, Paolo Borsa e Giulia Ravera.This volume on "Foscolo critico" is the first volume of the "Quaderni di Gargnano", an open access book series which publishes the Proceedings of the "Gennaro Barbarisi" International Conferences on Italian Literature, held in Gargnano del Garda. It contains contributions by Giovanni Biancardi, Arnaldo Bruni, Andrea Campana, Massimo Castellozzi, Gustavo Costa, Alfredo Cottignoli, Christian Del Vento, Sandro Gentili, Franco Longoni, Ilaria Mangiavacchi, Donatella Martinelli, Giuseppe Natale, Enzo Neppi, Matteo Palumbo, Elena Parrini Cantini, Chiara Piola Caselli, preceded by a Preface by the Editor: Claudia Berra, Paolo Borsa, Giulia Ravera

A Comprehensive assessment of the cross-training effect in ankle dorsiflexors of healthy subjects: a randomized controlled study

Purpose: To investigate the cross-training effect, induced on ankle dorsiflexors (AD) by unilateral strength-training of the contralateral muscles, as transfer of peak torque (PT) and muscle work (MW) and their relative contributions to muscle performance. Methods: Thirty healthy volunteers were randomly assigned to a training or control group. The trained group sustained a 4-week maximal isokinetic training of the stronger AD at 90 and 45°/s. At both angular velocities, PT, MW and MW/PT ratio were measured from both legs at baseline and after intervention (trained group) or no-intervention (controls). The familiarization/learning-effect was calculated and subtracted by PT and MW measures to obtain their net changes. Results: Net PT increased in both legs (untrained: +27.5% at 90°/s and +17.9% at 45°/s; trained: +15% at 90°/s and +16.3% at 45°/s). Similarly, net MW increased in both the untrained (90°/s: +29.6%; 45°/s: +37%) and trained (90°/s: +23.4%; 45°/s: +18.3%) legs. PT and MW gains were larger in the untrained than trained AD (p < 0.0005), with MW improving more than PT at 45°/s (p = 0.04). The MW/PT ratio increased bilaterally only in the trained group (p < 0.05), depending on the angular velocity. Conclusions: The cross-training effect occurred in AD muscles in terms of both PT and MW, with MW adding valuable information to PT-analysis in describing muscle performance. Moreover, the MW/PT ratio allowed estimating the contributions of these parameters to muscle capability and may represent a novel index in isokinetic testing. The greater improvements in the untrained than trained limb raises interesting clinical implications in asymmetric conditions