Non-gaussian probability distribution functions in two dimensional Magnetohydrodynamic turbulence

Intermittency in MHD turbulence has been analyzed using high resolution 2D numerical simulations. We show that the Probability Distribution Functions (PDFs) of the fluctuations of the Elsasser fields, magnetic field and velocity field depend on the scale at hand, that is they are self-affine. The departure of the PDFs from a Gaussian function can be described through the scaling behavior of a single parameter lambda_r^2 obtained by fitting the PDFs with a given curve stemming from the analysis of a multiplicative model by Castaing et al. (1990). The scaling behavior of the parameter lambda_r^2 can be used to extract informations about the intermittency. A comparison of intermittency properties in different MHD turbulent flows is also performed.Comment: 7 pages, with 5 figure

Morphological variation of the newly confirmed population of the javelin sand boa, Eryx jaculus (Linnaeus, 1758) (Serpentes, erycidae) in Sicily, Italy

The presence of the Javelin sand boa in Sicily has recently been confirmed. Here the morphological characters and sexual dimorphism of the Sicilian population of Eryx jaculus are presented. Seven meristic and six metric characters in 96 specimens from Sicily were examined. The results show that tail length, snout-vent length, the distance between nostrils and the number of ventral and subcaudal scales are different between sexes. The characters found in the Sicilian population of the Javelin sand boa resemble those of the African population (ssp. jaculus) rather than the Eurasian population (ssp. turcicus), but biomolecular studies are necessary to understand its taxonomic identity

Spettro trofico di due popolazioni sinantropiche di geco comune, Tarentola mauritanica (Linnaeus, 1758), in Sicilia sud-occidentale

The Moorish gecko (Tarentola mauritanica) is a lizard belonging to the Phyllodactylidae family, with circum-Mediterranean distribution. Despite the species is widespread in Sicily, there are very few studies on its feeding behaviour. This paper analyzes the diet of two synanthropic populations located in southwestern Sicily (province of Trapani) and exposed to different environmental conditions. Fecal remains were collected along the outer walls of an inhabited house in the coastal village of Triscina and in an uninhabited rural house, located near Castelvetrano town. The first study area has been constantly affected by artificial light sources, which are absent in the second study area. Results show in both cases that diets consist exclusively of arthropods, except for a single case of saurophagy on a juvenile Podarcis sp. detected in the \u2018Castelvetrano\u2019 sample. The two populations have significantly different trophic spectra and probably adopt two different foraging strategies. The \u2018Triscina\u2019 sample is characterized by the predominance of few categories of fliers prey generally concentrated by artificial light sources (Coleoptera 39.6%, Neuroptera 38.6%), suggesting the adoption of a \u2018sit-and-wait strategy\u2019. The \u2018Castelvetrano\u2019 sample is instead more varied and characterized by the prevalence of soil-related, and mostly wingless, prey (Dermaptera 36.7%, Formicidae 23.3%, Coleoptera 21.7%, spiders 11.7%), thus suggesting the adoption of an \u2018active foraging strategy\u2019

Census of the Sicilian rock partridge Alectoris graeca whitakeri population in ZPS ITA010029 Monte Cofano, Capo San Vito and Monte Sparagio

During the project "LIFE09 NAT/IT/000099-SICALECONS-Urgent actions for the conservation of Alectoris graeca whitakeri", this species was censused in the ZPS ITA010029 Monte Cofano, Capo San Vito and Monte Sparagio (Trapani province, Sicily) with playback technique between March and April 2011. Superimposing a UTM grid of 1 km mesh on the study area produced cells of 100 hectares. Using a GPS satellite receiver we reached, where possible, the centre of each cell from where the cospecific call was broadcasted. A total of 163 listening stations were implemented. Using software GIS ARCMAP 10.0 (ESRI) presence data were interpolated with vegetational and phytosociological maps (CORINE) to establish rock partridge's suitable area. The range of the rock partridge in the ZPS was calculated to be 9,893 hectares, corresponding to approximately 65% of the ZPS. A total of 29 individuals were counted, corresponding to 5 pairs and 19 calling males.The Sicilian rock partridge population in the ZPS was estimated to be 66 pairs. Density values in the ZPS were lower than those reported for other areas. In the ZPS highest density was observed in Zingaro Reserve, where poaching seems to be less frequent compared to other areas of ZPS and where burning has not been recorded for years. \ua9 2013 CISO - Centro Italiano Studi Ornitologici

First record of brown long-eared bat Plecotus auritus (Chiroptera: Vespertilionidae) for Sicily island (Italy)

The knowledge of the bat fauna of Sicily (Southern Italy) is scarce, fragmentary or sometimes even confusing. A recent review mentioned 20 species for the region, but it is likely that the checklist of bats of Sicily is still far from being exhaustive. To help fill this gap, in the past few years specific studies were carried out on the distribution of bat species in Sicily, especially in the woodlands of the Nebrodi Mountains. In the municipality of Caronia (Messina province) has captured a young female brown long-eared bat Plecotus auritus (Linneaus, 1758). The capture of P. auritus in Sicily represents the first record of brown long-eared bat Plecotus auritus for Sicily island, an interesting biogeographical record, as this bat is mostly known for the north and centre of the Italian peninsul

Free vibration analysis of sandwich plates with compressible core in contact with fluid

In this paper, the extended higher-order sandwich plate's theory (EHSAPT) is used to analyze the free vibration of the sandwich plate with compressible core and different boundary conditions in contact with fluid. First-order shear deformation theory is adopted for the top and bottom face sheets, while the in-plane and transverse displacements of the core are considered to be cubic and quadratic functions of the transverse coordinate, respectively. A single series is considered with two-variable orthogonal polynomials as a set of admissible functions satisfying the boundary conditions. Besides, the fluid is considered to be irrotational, inviscid and incompressible. By taking into account the boundary conditions and compatibility conditions, the fluid velocity potential is acquired. The natural frequencies of the system are calculated by the Rayleigh-Ritz method. An excellent accuracy is obtained between the results in the available literature and the present method. Finally, the effects of various parameters including boundary conditions, side-to-thickness ratio, thickness of the core to thickness of the face sheets ratio, face sheet to core flexural modulus ratio, dimensions of the container, and aspect ratios on the natural frequencies of the sandwich plate are presented and discussed in detail

Analysis of cancellation in two-dimensional magnetohydrodynamic turbulence

A signed measure analysis of two-dimensional intermittent magnetohydrodynamic turbulence is presented. This kind of analysis is performed to characterize the scaling behavior of the sign-oscillating flow structures, and their geometrical properties. In particular, it is observed that cancellations between positive and negative contributions of the field inside structures, are inhibited for scales smaller than the Taylor microscale, and stop near the dissipative scale. Moreover, from a simple geometrical argument, the relationship between the cancellation exponent and the typical fractal dimension of the structures in the flow is obtained.Comment: 21 pages, 5 figures (3 .jpg not included in the latex file

Coherent structures and spectral energy transfer in turbulent plasma: A space-filter approach

Plasma turbulence at scales of the order of the ion inertial length is mediated by several mechanisms, including linear wave damping, magnetic reconnection, the formation and dissipation of thin current sheets, and stochastic heating. It is now understood that the presence of localized coherent structures enhances the dissipation channels and the kinetic features of the plasma. However, no formal way of quantifying the relationship between scale-to-scale energy transfer and the presence of spatial structures has been presented so far. In the Letter we quantify such a relationship analyzing the results of a two-dimensional high-resolution Hall magnetohydrodynamic simulation. In particular, we employ the technique of space filtering to derive a spectral energy flux term which defines, in any point of the computational domain, the signed flux of spectral energy across a given wave number. The characterization of coherent structures is performed by means of a traditional two-dimensional wavelet transformation. By studying the correlation between the spectral energy flux and the wavelet amplitude, we demonstrate the strong relationship between scale-to-scale transfer and coherent structures. Furthermore, by conditioning one quantity with respect to the other, we are able for the first time to quantify the inhomogeneity of the turbulence cascade induced by topological structures in the magnetic field. Taking into account the low space-filling factor of coherent structures (i.e., they cover a small portion of space), it emerges that 80% of the spectral energy transfer (both in the direct and inverse cascade directions) is localized in about 50% of space, and 50% of the energy transfer is localized in only 25% of space