Delay time in the transfer of modulation between microwave beams

AbstractMeasurements of delay time relative to the signal transferred from a modulated beam F2 to an unmodulated one F1, both of which operate with a microwave carrier at ∼9.3 GHz, are reported and interpreted. The observed behavior is open to two possible interpretations: one is based on a purely stochastic model that consists of zigzag random paths; the other is based on a more conventional electromagnetic approach, although it maintains some of the characteristics of the stochastic model. The anomalous behaviors here studied can have significant applications in photonics and electro‐optics

Anomalous cross-modulation between microwave beams

Abstract An anomalous effect in the near field of crossing microwave beams, which consists of an unexpected transfer of modulation from one beam to the other, has found a plausible interpretation within the framework of a locally broken Lorentz invariance. A theoretical approach of this kind deserves to be reconsidered also in the light of further experimental work, including a counter-check of the phenomenon

Monitoring of coastal dunes habitats in Tuscany through the “MONITO-RARE” project

“MONITO-RARE” is a project involving Tuscany Region and Universities of Firenze, Siena and Pisa, aimed to improve the knowledge and develop monitoring methodologies for species and habitats included in Natura 2000 Network and considered of community interest, according to Art. 11 and Art. 17 of the Directive 92/43/EEC. Among the habitat of interest (Annex I), coastal sand dune is one of the most threatened by multiple human pressures (1, 2), such as pollution, coastal erosion, effects of global warming, farming practices, urban development, and pressure from tourism (3). As part of this project, was carried out a first year of monitoring of dunal habitats (Natura 200 code 2110, 2120, 2210, 2230, 2240, 2250* and 2260) in five SACs (Special Areas of Conservation) in order to cover different latitudes of Tuscany coast (“Dune litoranee di Torre del Lago/Selva Pisana”, “Tombolo da Castiglion della Pescaia a Marina di Grosseto”, “Dune costiere del Parco dell’Uccellina” and “Duna del Lago di Burano”). The coastal areas to the north and south of Arno basin are very different by climatic, geomorphologic (erosion) and anthropic factors. The northern coast is twice rainy as the southern one. Nevertheless, sand dune habitats are distributed in a fine scale mosaic, not distinguishable through aerial photos and maps. For this reason, we opted for a stratified sampling in three EUNIS habitat types (B1.3, shifting coastal dunes; B1.4, coastal stable dune grassland; B1.6, coastal dune scrub) for psammophilous vegetation. According to Sperandii et al. (4), we recorded these communities by 262 random plots of 2 x 2 m surface in which were surveyed pressures and threats, floristic composition and an estimate of abundance using a percentage cover scale ranging from 1 to 10. Our sampling is congruent with RanVegDunes (GIVD ID EU-IT-020), the first Italian database gathering standardized, randomly-sampled vegetation data in coastal dune environments. We detected significative differences in abundance and species composition between EUNIS habitat types, between SACs, and between habitat types within SACs. In particular, our data shows particular differences between communities of north and south of Tuscany: the northern SACs to Serchio river are heavily impacted by the presence of mass tourism, with bathing establishments, roads and human trampling. From these evidences can be deduced that trails installed within the DUNETOSCA Life Projects and aimed to reduction of tourism impact may be insufficient to reduce anthropic pressures in those contexts and adequate conservation strategies are required. 1) EEA (1999) State and pressures of the marine and coastal Mediterranean Environment. Environmental Issues Series, No. 5, European Environment Agency, Copenhagen 2) Barcelona Convention, Athens (2012) UNEP/MAP 2012. State of the Mediterranean Marine and Coastal Environment https://wedocs.unep.org/bitstream/handle/20.500.11822/364/sommcer_eng.pdf?sequence=4&isAllowed=y 3) Ciccarelli D. (2014) Environmental Management 54, 194–204 4) Sperandii M.G., Prisco I., Stanisci A., Acosta A.T.R. (2017) Phytocoenologia 47, 231–23

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

FIRST TESTS OF A TORALDO PUPIL OPTICAL MODULE FOR THE 32M MEDICINA ANTENNA

Toraldo Pupils can improve the angular resolving power of an optical instrument beyond the classical diffraction limit (hence the term “super-resolution”) using a filter consisting of finite- width concentric coronae with different amplitude and phase transmittance. Toraldo Pupils represent a viable approach to achieve super-resolution on antennas and radio telescopes. In this work we present a summary of the electromagnetic simulations and laboratory tests of a prototype optical module based on a Toraldo Pupil that has been field-tested on the Medicina 32-m radio telescope

Intraspecific variability of leaf form and function across habitat types

: Trait-based ecology has already revealed main independent axes of trait variation defining trait spaces that summarize plant adaptive strategies, but often ignoring intraspecific trait variability (ITV). By using empirical ITV-level data for two independent dimensions of leaf form and function and 167 species across five habitat types (coastal dunes, forests, grasslands, heathlands, wetlands) in the Italian peninsula, we found that ITV: (i) rotated the axes of trait variation that define the trait space; (ii) increased the variance explained by these axes and (iii) affected the functional structure of the target trait space. However, the magnitude of these effects was rather small and depended on the trait and habitat type. Our results reinforce the idea that ITV is context-dependent, calling for careful extrapolations of ITV patterns across traits and spatial scales. Importantly, our study provides a framework that can be used to start integrating ITV into trait space analyses