Search results for " Fisica Matematica"
showing 10 items of 384 documents
(H,ρ)-induced dynamics and large time behaviors
2018
In some recent papers, the so called (H,ρ)-induced dynamics of a system S whose time evolution is deduced adopting an operatorial approach, borrowed in part from quantum mechanics, has been introduced. Here, H is the Hamiltonian for S, while ρ is a certain rule applied periodically (or not) on S. The analysis carried on throughout this paper shows that, replacing the Heisenberg dynamics with the (H,ρ)-induced one, we obtain a simple, and somehow natural, way to prove that some relevant dynamical variables of S may converge, for large t, to certain asymptotic values. This cannot be so, for finite dimensional systems, if no rule is considered. In this case, in fact, any Heisenberg dynamics im…
The BepiColombo MORE gravimetry and rotation experiments with the ORBIT14 software
2016
The BepiColombo mission to Mercury is an ESA/JAXA cornerstone mission, consisting of two spacecraft in orbit around Mercury addressing several scientific issues. One spacecraft is the Mercury Planetary Orbiter, with full instrumentation to perform radio science experiments. Very precise radio tracking from Earth, on-board accelerometer and optical measurements will provide large data sets. From these it will be possible to study the global gravity field of Mercury and its tidal variations, its rotation state and the orbit of its centre of mass. With the gravity field and rotation state, it is possible to constrain the internal structure of the planet. With the orbit of Mercury, it is possib…
Modelling prey-predator interactions in Messina beachrock pools
2020
Abstract The Strait of Messina (Sicily, Italy) attracts the interest of marine ecologists for the presence of a large variety of habitat and mutually-interacting communities. Among them, beachrock formations, despite their wide geographic distribution, which also includes the Mediterranean area, have been poorly investigated from the biotic viewpoint. In this paper, the spatial and seasonal variability of benthic megafauna from the Messina microtidal beachrock is described. Combining in situ collected data (measurements of abiotic parameters and underwater visual census) with theoretical post-processing analyses (analysis of similarity percentages and cluster analysis), we deduced the possi…
Predictive distribution models of European hake in the south-central Mediterranean Sea
2017
The effective management and conservation of fishery resources requires knowledge of their spatial distribution and notably of their critical life history stages. Predictive modelling of the European hake (Merluccius merluccius L., 1758) distribution was developed in the south-central Mediterranean Sea by means of historical fisheries-independent databases available in the region. The study area included the international waters of the south-central Mediterranean Sea and the territorial waters of Italy, Malta, Tunisia and Libya. Distribution maps of predicted population abundance index, and probabilistic occurrence of recruits and large adults were obtained by means of generalized additive …
Exploring connectivity between spawning and nursery areas ofMullus barbatus(L., 1758) in the Mediterranean through a dispersal model
2017
Connectivity between spawning and nursery areas plays a major role in determining the spatial structure of fish populations and the boundaries of stock units. Here, the potential effects of surface current on a red mullet population in the Central Mediterranean were simulated using a physical oceanographic model. Red mullet larvae were represented as Lagrangian drifters released in known spawning areas of the Strait of Sicily (SoS), which represents one of the most productive demersal fishing-grounds of the Mediterranean. To consider the effect of inter-annual variability of oceanographic patterns, numerical simulations were performed for the spawning seasons from 1999 to 2012. The main goa…
Two simple criteria to estimate an objective's performance when imaging in non design tissue clearing solutions
2019
Tissue clearing techniques are undergoing a renaissance motivated by the need to image fluorescent neurons, and other cells, deep in the sample without physical sectioning. Optical transparency is achieved by equilibrating tissues with high refractive index (RI) solutions. When the microscope objective is not perfectly matched to the RI of the cleared sample, aberrations are introduced. We present two simple-to-calculate numerical criteria predicting: (i) the degradation in image quality (brightness and resolution) from optimal conditions of any clearing solution/objective combination; (ii) which objective, among several available, achieves the highest resolution in a given medium. We deriv…
On the structural connectivity of large-scale models of brain networks at cellular level
2021
AbstractThe brain’s structural connectivity plays a fundamental role in determining how neuron networks generate, process, and transfer information within and between brain regions. The underlying mechanisms are extremely difficult to study experimentally and, in many cases, large-scale model networks are of great help. However, the implementation of these models relies on experimental findings that are often sparse and limited. Their predicting power ultimately depends on how closely a model’s connectivity represents the real system. Here we argue that the data-driven probabilistic rules, widely used to build neuronal network models, may not be appropriate to represent the dynamics of the …
Structure of locally convex quasi C * -algebras
2008
There are examples of C*-algebras A that accept a locally convex *-topology τ coarser than the given one, such that Ã[τ] (the completion of A with respect to τ) is a GB*-algebra. The multiplication of A[τ] may be or not be jointly continuous. In the second case, Ã[*] may fail being a locally convex *-algebra, but it is a partial *-algebra. In both cases the structure and the representation theory of Ã[τ] are investigated. If Ã+ τ denotes the τ-closure of the positive cone A+ of the given C*-algebra A, then the property Ā+ τ ∩ (-Ā+ τ) = {0} is decisive for the existence of certain faithful *-representations of the corresponding *-algebra Ã[τ]
Universal spectral profile and dynamic evolution of muscle activation: A hallmark of muscle type and physiological state
2020
The skeletal muscle is an integrated multicomponent system with complex dynamics of continuous myoelectrical activation of various muscle types across time scales to facilitate muscle coordination among units and adaptation to physiological states. To understand the multiscale dynamics of neuromuscular activity, we investigated spectral characteristics of different muscle types across time scales and their evolution with physiological states. We hypothesized that each muscle type is characterized by a specific spectral profile, reflecting muscle composition and function, that remains invariant over time scales and is universal across subjects. Furthermore, we hypothesized that the myoelectr…
Longitudinal Study on Sustained Attention to Response Task (SART): Clustering Approach for Mobility and Cognitive Decline
2022
The Sustained Attention to Response Task (SART) is a computer-based go/no-go task to measure neurocognitive function in older adults. However, simplified average features of this complex dataset lead to loss of primary information and fail to express associations between test performance and clinically meaningful outcomes. Here, we combine a novel method to visualise individual trial (raw) information obtained from the SART test in a large population-based study of ageing in Ireland and an automatic clustering technique. We employed a thresholding method, based on the individual trial number of mistakes, to identify poorer SART performances and a fuzzy clusters algorithm to partition the da…