The Screen representation of spin networks: 2D recurrence, eigenvalue equation for 6j symbols, geometric interpretation and Hamiltonian dynamics

This paper treats 6j symbols or their orthonormal forms as a function of two variables spanning a square manifold which we call the "screen". We show that this approach gives important and interesting insight. This two dimensional perspective provides the most natural extension to exhibit the role of these discrete functions as matrix elements that appear at the very foundation of the modern theory of classical discrete orthogonal polynomials. Here we present 2D and 1D recursion relations that are useful for the direct computation of the orthonormal 6j, which we name U. We present a convention for the order of the arguments of the 6j that is based on their classical and Regge symmetries, and a detailed investigation of new geometrical aspects of the 6j symbols. Specifically we compare the geometric recursion analysis of Schulten and Gordon with the methods of this paper. The 1D recursion relation, written as a matrix diagonalization problem, permits an interpretation as a discrete Schr\"odinger-like equations and an asymptotic analysis illustrates semiclassical and classical limits in terms of Hamiltonian evolution.Comment: 14 pages,9 figures, presented at ICCSA 2013 13th International Conference on Computational Science and Applicatio

Habitat fragmentation and anthropogenic factors affect wildcat Felis silvestris silvestris occupancy and detectability on Mt Etna

Knowledge of patterns of occupancy is crucial for planning sound biological management and for identifying areas which require paramount conservation attention. The European wildcat Felis silvestris is an elusive carnivore and is classified as ‘least concern’ on the IUCN red list, but with a decreasing population trend in some areas. Sicily hosts a peculiar wildcat population, which deserves conservation and management actions, due to its isolation from the mainland. Patterns of occupancy for wildcats are unknown in Italy, and especially in Sicily. We aimed to identify which ecological drivers determined wildcat occurrence on Mt Etna and to provide conservation actions to promote the wildcats’ long-term survival in this peculiar environment. The genetic identity of the wildcat population was confirmed through a scat-collection which detected 22 different wildcat individuals. We analysed wildcat detections collected by 91 cameras using an occupancy frame work to assess which covariates influenced the detection (p) and the occupancy (ψ) estimates. We recorded 70 detections of the target species from 38 cameras within 3377 trap-days. Wildcat detection was positively influenced by the distance to the major paved roads and negatively affected by the presence of humans. Wildcat occupancy was positively associated with mixed forest and negatively influenced by pine forest, fragmentation of mixed forest and altitude. A spatially explicit predicted occupancy map, validated using an independent dataset of wildcat presence records, showed that higher occupancy estimates were scattered, mainly located on the north face and at lower altitude. Habitat fragmentation has been claimed as a significant threat for the wildcat and this is the first study that has ascertained this as a limiting factor for wildcat occurrence. Conservation actions should promote interconnectivity between areas with high predicted wildcat occupancy while minimising the loss of habitat

The screen representation of vector coupling coefficients or Wigner 3j symbols: exact computation and illustration of the asymptotic behavior

The Wigner $3j$ symbols of the quantum angular momentum theory are related to the vector coupling or Clebsch-Gordan coefficients and to the Hahn and dual Hahn polynomials of the discrete orthogonal hyperspherical family, of use in discretization approximations. We point out the important role of the Regge symmetries for defining the screen where images of the coefficients are projected, and for discussing their asymptotic properties and semiclassical behavior. Recursion relationships are formulated as eigenvalue equations, and exploited both for computational purposes and for physical interpretations.Comment: 14 pages, 8 figures, presented at ICCSA 2014, 14th International Conference on Computational Science and Application

Analysis of driving seat vibrations in different transfer conditions

The vibration transmitted through the seat of a four-wheel drive tractor, developing 179 kW, and equipped with front suspension axle and shock absorber for the implement, were measured and analysed according to the ISO standard. Several tests were carried out in different conditions considering: type of operation (transfer with and without mounted implement); type of track (conglomerate bituminous road, country lane); connected and disconnected suspension and/or shock absorber; and forward speeds. For the transfer on bituminous conglomerate road, it was observed that the suspension always reduces acceleration av, in both tests without and with implement, for all the considered forward speeds. For the tests conduced on country lane, the front axle suspension involved a reduction of the acceleration, but it was less evident than on the road Results showed that the forward speed and the mass distribution were the most important factors on tractor behaviour influencing the driver comfort. The daily exposure time which could compromise the driver's health increased from 2.5 to 8 h decreasing the speed from 3.06 to 2.22 m/s during transfer in country lane without implement. In the other condition the time exposure is approximately more than a working day

Wild and Farmed Sea Bass (Dicentrarchus Labrax): Comparison of Biometry Traits, Chemical and Fatty Acid Composition of Fillets

Sea bass is a fish widely produced, consumed and appreciated in Italy. Its intensive rearing system provides the consumption of valuable fish to a wider population. Thanks to the use of an appropriate feed, it is possible to obtain reared sea bass which are richer in total lipid with a majority presence of polyunsaturated fatty acids, such as n-3 and n-6 series. In this study, a total of 75 specimens of European sea bass coming from three different origins (two farmed and one wild) were considered, with 25 fish from each origin. Biometry traits were valued as of the chemical and fatty acid profile of fillets. Biometric indices, proximate composition and fatty acid percentage were significantly affected by the rearing system. Fishes from the intensive rearing system (IRS) showed the highest value of relative profile and condition factor, a higher content of lipid and total n-6 that influenced the n-6/n-3 ratio and the atherogenic indexes, and values that indicated their flesh for human consumption as a healthy alternative to the wild fishes

Meat quality and lipid fatty acid profile from wild thrush (Turdus philomelos), woodcock (Scolopax rusticola) and starling (Sturnus vulgaris): A preliminary comparative study

Background: The present study aimed to evaluate the nutritional proximate composition, some qualitative traits and fatty acid profile of meat from wild thrush, woodcock and starling hunted in Southern Italy in 2017 and 2018. Methods: Nutritive composition and physical traits of meat and lipid fatty acid profile were evaluated in breast muscle (Pectoralis major) of gamebirds. Results: From findings, the meat pH was significantly (P < 0.001) higher in starling when compared to the other two species. Thrush meat was significantly (P = 0.002) darker and had higher redness (P < 0.001) and yellowness (P = 0.004) in comparison to starling and woodcock. Thrush breast muscle showed the highest (P < 0.001) level of lipids and lowest (P < 0.001) protein content. Meat from thrush showed the best lipid fatty acid profile based on the higher (P < 0.001) monounsaturated fatty acids (MUFA) and lower (P < 0.001) saturated fatty acids (SFA) concentrations. Starling breast muscle reported the highest (P = 0.002) polyunsaturated fatty acids (PUFA) level compared to both thrush and woodcock, whereas no differences were detected on total n-3. The ratio n-6/n-3 was higher (P = 0.001) in starling muscle. Thrush breast muscle had the lowest (P < 0.001) atherogenic and thrombogenic indices compared to the other gamebirds. Conclusions: The findings indicated that meat from the three investigated gamebirds species may represent a healthily lipid food source for human consumption in relation to the prevention of cardiovascular diseases