Ray-tracing and physical-optics analysis of the aperture efficiency in a radio telescope

The performance of telescope systems working at microwave or visible/IR wavelengths is typically described in terms of different parameters according to the wavelength range. Most commercial ray tracing packages have been specifically designed for use with visible/IR systems and thus, though very flexible and sophisticated, do not provide the appropriate parameters to fully describe microwave antennas, and thus to compare with specifications. In this work we demonstrate that the Strehl ratio is equal to the phase efficiency when the apodization factor is taken into account. The phase efficiency is the most critical contribution to the aperture efficiency of an antenna, and the most difficult parameter to optimize during the telescope design. The equivalence between the Strehl ratio and the phase efficiency gives the designer/user of the telescope the opportunity to use the faster commercial ray-tracing software to optimize the design. We also discuss the results of several tests performed to check the validity of this relationship that we carried out using a ray-tracing software, ZEMAX and a full Physical Optics software, GRASP9.3, applied to three different telescope designs that span a factor of $\simeq 10 in terms of D/lambda. The maximum measured discrepancy between phase efficiency and Strehl ratio varies between$\simeq 0.4 and 1.9 up to an offset angle of >40 beams, depending on the optical configuration, but it is always less than 0.5 where the Strehl ratio is >0.95.Comment: 34 pages, 7 figure

Methods for a quantitative evaluation of odd-even staggering effects

Odd-even effects, also known as "staggering" effects, are a common feature observed in the yield distributions of fragments produced in different types of nuclear reactions. We review old methods, and we propose new ones, for a quantitative estimation of these effects as a function of proton or neutron number of the reaction products. All methods are compared on the basis of Monte Carlo simulations. We find that some are not well suited for the task, the most reliable ones being those based either on a non-linear fit with a properly oscillating function or on a third (or fourth) finite difference approach. In any case, high statistic is of paramount importance to avoid that spurious structures appear just because of statistical fluctuations in the data and of strong correlations among the yields of neighboring fragments.Comment: 16 pages, 9 figures - Revised version, mainly with an expanded sect. 2 about smoothing methods (three more methods are presented and an appendix on relevant aspects of the finite-differences formalism is added); results are shown also for the simulations with the three additional methods. Some more references are added. Conclusions are unchange

Modeling Radio Circular Polarization in the Crab Nebula

In this paper we present, for the first time, simulated maps of the circularly polarized synchrotron emission from the Crab nebula, using multidimensional state of the art models for the magnetic field geometry. Synchrotron emission is the signature of non-thermal emitting particles, typical of many high-energy astrophysical sources, both Galactic and extra-galactic ones. Its spectral and polarization properties allow us to infer key informations on the particles distribution function and magnetic field geometry. In recent years our understanding of pulsar wind nebulae has improved substantially thanks to a combination of observations and numerical models. A robust detection or non-detection of circular polarization will enable us to discriminate between an electron-proton plasma and a pair plasma, clarifying once for all the origin of the radio emitting particles, setting strong constraints on the pair production in pulsar magnetosphere, and the role of turbulence in the nebula. Previous attempts at measuring the circular polarization have only provided upper limits, but the lack of accurate estimates, based on reliable models, makes their interpretation ambiguous. We show here that those results are above the expected values, and that current polarimetric tecniques are not robust enough for conclusive result, suggesting that improvements in construction and calibration of next generation radio facilities are necessary to achieve the desired sensitivity.Comment: 5 pages, 2 figures, accepted for publication in MNRA

Chimera states in pulse coupled neural networks: the influence of dilution and noise

We analyse the possible dynamical states emerging for two symmetrically pulse coupled populations of leaky integrate-and-fire neurons. In particular, we observe broken symmetry states in this set-up: namely, breathing chimeras, where one population is fully synchronized and the other is in a state of partial synchronization (PS) as well as generalized chimera states, where both populations are in PS, but with different levels of synchronization. Symmetric macroscopic states are also present, ranging from quasi-periodic motions, to collective chaos, from splay states to population anti-phase partial synchronization. We then investigate the influence disorder, random link removal or noise, on the dynamics of collective solutions in this model. As a result, we observe that broken symmetry chimera-like states, with both populations partially synchronized, persist up to 80 \% of broken links and up to noise amplitudes 8 \% of threshold-reset distance. Furthermore, the introduction of disorder on symmetric chaotic state has a constructive effect, namely to induce the emergence of chimera-like states at intermediate dilution or noise level.Comment: 15 pages, 7 figure, contribution for the Workshop "Nonlinear Dynamics in Computational Neuroscience: from Physics and Biology to ICT" held in Turin (Italy) in September 201

Anteon ephippiger (Dalman, 1818) (Hymenoptera, Dryinidae) : a new dryinid record for the Maltese entomofauna

Short correspondence article about the Dryinidae family of wasps. The article mentions the only 3 records of this dryinid for the Maltese Islands.peer-reviewe

A New Species of Anteon (Hymenoptera: Dryinidae) from Argentina

Se describe la nueva especie Anteon tucumanense de San Miguel de Tucumán (Provincia de Tucumán, Argentina). A. tucumanense puede ser diferenciada de las especies neotropicales relacionadas, A. molle Olmi y A. parkeri Olmi, por diferencias en la forma del quinto segmento de los tarsos anteriores (con la parte distal ancha, robusta y derecha en A. tucumanense; con la parte distal angosta, delicada y curva en las otras dos especies). Se provee una clave para la determinación de las especies antedichas y la ilustración de la quela de la nueva especie.A new species, Anteon tucumanense, is described from San Miguel de Tucumán (Tucumán Province, Argentina). This new species can be distinguished from the related Neotropical species A. molle Olmi and A. parkeri Olmi by differences in segment 5 of the fore tarsus (distal part large and straight in A. tucumanense, slender and curved in the other 2 species). A key is provided for the determinations of the above species with an illustration of the female chela of the new species.Fil: Olmi, Massimo. Universita Degli Studi Della Tuscia; ItaliaFil: Virla, Eduardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentin

Description of Bocchus irwini sp. nov. from Madagascar (Hymenoptera Dryinidae)

Bocchus irwini sp. nov. is described from a male collected in Analagnambe forest, Mahajanga Province, Madagascar. The new species is similar to Bocchus watshami Olmi 1987. Keys to the Afrotropical species of Bocchus are modified to include the new species