Fauna di Sicilia. Anfibi

An agent based model of air traffic management

The WP-E ELSA project aims at developing an empirically grounded agent based model that describes some of the stylized facts observed in the Air Traffic Management of the European airspace. The model itself has two main parts: (i) The strategic layer, focused on the interaction between the Network Manager and the Airline Operators and (ii) the tactical layer, focused on aircraft and controllers behaviour in Air Traffic Control (ATC) sectors. The preliminary results for the strategic layer show that when we have a mixing of re-routing and shifting companies, the overall satisfaction can even increase together with the number of flights, which is an effect not observed when only one type of c…

Primi dati sull’uso dell’habitat in una popolazione siciliana di Natrix natrix.

First data about the habitat use in a population of Natrix natrix from Sicily. In the present paper the preliminary results of an investigation carried out on a Sicilian population of the grass snake (Natrix natrix) are reported. The leading aim of this study is to compare habitat use among three different classes of individuals (males, females, immatures), using as input the density of observations in four habitat types. Field studies were conducted beside a reservoir (“Lago di Scanzano”), located about 40 km from Palermo (western Sicily). Our results indicate spatial and temporal differences among groups. Young individuals were observed more frequently between April and May along wet mead…

Shrinkage and spectral filtering of correlation matrices: A comparison via the Kullback-Leibler distance

The problem of filtering information from large correlation matrices is of great importance in many applications. We have recently proposed the use of the Kullback-Leibler distance to measure the performance of filtering algorithms in recovering the underlying correlation matrix when the variables are described by a multivariate Gaussian distribution. Here we use the Kullback-Leibler distance to investigate the performance of filtering methods based on Random Matrix Theory and on the shrinkage technique. We also present some results on the application of the Kullback-Leibler distance to multivariate data which are non Gaussian distributed.

Sector identification in a set of stock return time series traded at the London Stock Exchange

We compare some methods recently used in the literature to detect the existence of a certain degree of common behavior of stock returns belonging to the same economic sector. Specifically, we discuss methods based on random matrix theory and hierarchical clustering techniques. We apply these methods to a portfolio of stocks traded at the London Stock Exchange. The investigated time series are recorded both at a daily time horizon and at a 5-minute time horizon. The correlation coefficient matrix is very different at different time horizons confirming that more structured correlation coefficient matrices are observed for long time horizons. All the considered methods are able to detect econo…

Adaptative air traffic network: Statistical regularities in air traffic management

Starting from traffic data on flights trajectories-planned and actual ones-in Europe, we build a navigation point network. We study this network which exhibits different features for different European countries. In particular, some countries uses a high number of navpoints, facilitating the planning of the flight plan by air companies at the cost of higher concentrations of traffic in few nodes. Making use of the deviations from the planned trajectories, we find that once again different countries have different control procedures with respect to traffic management. Interestingly, we find that some countries tend to make more deviations when the traffic conditions are low. Moreover, they t…

ELSA Project: Toward a complex network approach to ATM delays analysis

The paper presents the preliminary results delivered by the WPE project ELSA. After some introductory notes about the project aims and structure, the paper shows how tools borrowed by the Complex Network Theory can be used to study the issue of delays in the air traffic system.

Primi risultati di un progetto di restocking di Testuggine

First results of a restocking project for Testudo hermanni in a protected area in northwestern Sicily. A restocking project was carried out in the Zingaro Natural Reserve in order to counteract the Sicilian population decrease of Testudo hermanni. 50 tortoises coming from regional wildlife rescue centers were released after an acclimatization period in a controlled fence. 11 tortoises have been provided with radio-transmitters to follow the dispersal process and to monitoring the project progress. The obtained results have permitted to assess the useful area for the dispersion during the first year from the release and have showed the successful integration of the rescued tortoises with the…

Differenze intersessuali nella dieta in una popolazione di Rospo smeraldino siciliano Bufo siculus (Stock et al., 2008)

Co-circulation of SARS-CoV-2 Alpha and Gamma variants in Italy, February and March 2021

Background Several SARS-CoV-2 variants of concern (VOC) have emerged through 2020 and 2021. There is need for tools to estimate the relative transmissibility of emerging variants of SARS-CoV-2 with respect to circulating strains. Aim We aimed to assess the prevalence of co-circulating VOC in Italy and estimate their relative transmissibility. Methods We conducted two genomic surveillance surveys on 18 February and 18 March 2021 across the whole Italian territory covering 3,243 clinical samples and developed a mathematical model that describes the dynamics of co-circulating strains. Results The Alpha variant was already dominant on 18 February in a majority of regions/autonomous provinces (…

Statistical Regularities in ATM: network properties, trajectory deviations and delays

One of the key enabler to the productivity and efficiency shift foreseen by SESAR will be the business-trajectory concept. The path to a deep understanding of how this new concept impacts on the future SESAR Air Traffic Management scenario goes through a better understanding of the actual air traffic network, and this will be done in the present paper by analyzing traffic data within the framework of complex network analysis. In this paper we will consider flights trajectory data from the Data Demand Repository database. In a first investigation, we perform a network study of the air traffic infrastructure starting from the airports and then refining our analysis at the level of navigation …