Search results for "Actor"
showing 10 items of 19159 documents
Singular tori as attractors of four-wave-interaction systems
2009
We study the spatiotemporal dynamics of the Hamiltonian four-wave interaction in its counterpropagating configuration. The numerical simulations reveal that, under rather general conditions, the four-wave system exhibits a relaxation process toward a stationary state. Considering the Hamiltonian system associated to the stationary state, we provide a global geometrical view of all the stationary solutions of the system. The analysis reveals that the stationary state converges exponentially toward a pinched torus of the Hamiltonian system in the limit of an infinite nonlinear medium. The singular torus thus plays the role of an attractor for the spatiotemporal wave system. The topological pr…
Modelling Systemic Cojumps with Hawkes Factor Models
2013
Instabilities in the price dynamics of a large number of financial assets are a clear sign of systemic events. By investigating a set of 20 high cap stocks traded at the Italian Stock Exchange, we find that there is a large number of high frequency cojumps. We show that the dynamics of these jumps is described neither by a multivariate Poisson nor by a multivariate Hawkes model. We introduce a Hawkes one factor model which is able to capture simultaneously the time clustering of jumps and the high synchronization of jumps across assets.
Hadronic light-by-light contribution to $(g-2)_\mu$ from lattice QCD with SU(3) flavor symmetry
2020
We perform a lattice QCD calculation of the hadronic light-by-light contribution to $(g-2)_\mu$ at the SU(3) flavor-symmetric point $m_\pi=m_K\simeq 420\,$MeV. The representation used is based on coordinate-space perturbation theory, with all QED elements of the relevant Feynman diagrams implemented in continuum, infinite Euclidean space. As a consequence, the effect of using finite lattices to evaluate the QCD four-point function of the electromagnetic current is exponentially suppressed. Thanks to the SU(3)-flavor symmetry, only two topologies of diagrams contribute, the fully connected and the leading disconnected. We show the equivalence in the continuum limit of two methods of computin…
Protein levels of brain-derived neurotrophic factor in the hippocampus of low/high aerobic capacity rats
2010
Hippocrates and Plato have first documented the connection between a healthy mind and body, during a period which launched analytical thinking and philosophy in Ancient Greece. Modern research has also indicated the contribution of an active lifestyle to enhanced brain performance and decreased incidence of neurodegenerative diseases and mood disorders such as Alzheimer’s disease and depression respectively. This has been hypothesized to emerge through mechanisms which are enhanced by exercise and contribute on brain plas-ticity and health. The Neurotrophins hypothesis implicates several molecules in brain plasticity and healthy aging. Among them, Brain-derived Neurotrophic Factor (BDNF) ha…
Modelling and assessing public health policies to counteract Italian measles outbreaks
2021
This study aims to understand, through explanatory research, the key factors that led to the 2017 measles outbreak in Italy, the causes of the low level of immunisation and the causes of possible cyclical phenomena of measles epidemics. This topic's comprehension has required a holistic approach, merging epidemiological aspects, socioeconomic aspects (including the evolution of mistrust in vaccinations, infodemy and fake news) and health law constraints. A specific SIR System Dynamics (SD) model was built to reproduce the relevant cause-and-effect relationships between social interactions, the public institutions behaviour and the measles outbreaks. SD results permit the assessment of the h…
Coexistence of hidden attractors and multistability in counterexamples to the Kalman conjecture
2019
The Aizerman and Kalman conjectures played an important role in the theory of global stability for control systems and set two directions for its further development – the search and formulation of sufficient stability conditions, as well as the construction of counterexamples for these conjectures. From the computational perspective the latter problem is nontrivial, since the oscillations in counterexamples are hidden, i.e. their basin of attraction does not intersect with a small neighborhood of an equilibrium. Numerical calculation of initial data of such oscillations for their visualization is a challenging problem. Up to now all known counterexamples to the Kalman conjecture were const…
Estudio multidisciplinar de la Muerte Súbita e Inesperada del Lactante en la Comunidad Valenciana. 2006-2017. Estrategia de análisis y prevención
2020
El síndrome de la muerte súbita del lactante (SMSL) define la muerte súbita de un niño menor de un año de edad, que ocurre aparentemente durante el sueño y que permanece sin explicación después de la realización de una minuciosa investigación postmortem, que incluye la autopsia completa, la investigación de las circunstancias de la muerte y la revisión de la historia clínica. La etiopatogenia del SMSL se ha entendido a través de la hipótesis del triple riesgo. Las tasas de incidencia del SMSL, han ido descendiendo drásticamente situándose en la actualidad en 0,2 -0,5 por mil nacimientos vivos, manteniéndose estable en los últimos años. Los factores de riesgo relacionados con el sueño del la…
Factorial Validity of the "Spanish Burnout Inventory" (SBI) in a Sample of Mexican Doctors
2010
El objetivo del estudio fue evaluar la validez factorial del Cuestionario para la Evaluación del Síndrome de Quemarse por el Trabajo (CESQT). Se hipotetizó un modelo de cuatro factores. La muestra estuvo compuesta por 110 médicos del Instituto Mexicano del Seguro Social. El instrumento está formado por 20 ítems distribuidos en 4 subescalas: Ilusión por el trabajo (5 ítems), Desgaste psíquico (4 ítems), Indolencia (6 ítems), y Culpa (5 ítems). El modelo presentó un ajuste adecuado: GFI = .83, RMSEA = .061, NNFI = .90, CFI = .92, PNFI = .65. Los resultados indican que el CESQT presentó en esta muestra validez factorial y valores de consistencia interna adecuados. The purpose of this study was…
Genetic Factors as Promising Biomarkers of Sporadic Ascending Aortic Aneurysm
2014
Thoracic aorta shows various changes with advancing age and a progressive deterioration in structure and function. As a result, vascular remodeling (VR) and medial degeneration (MD) occur. VR and MD are typical entities of sporadic thoracic aortic aneurysm (TAA), actually considered a common and serious health risk and a pathology by unclear mechanisms. Increased activity of the coagulation system, inflammation, activation of extracellular matrix remodeling and endothelial dysfunction pathways have been recently evidenced to have a key role in its onset. Thus, polymorphisms of the coagulation system [fibrinogen (rs1800790); Factor II ( rs1799963); Factor V (rs6025); Factor VII (rs121964926)…
Depressive symptoms during adolescence: Do learning difficulties matter?
2011
To examine whether learning difficulties play a role in depressive symptoms, 658 Finnish adolescents were asked to complete scales for depression three times during the transition to post-comprehensive education. They also reported on their learning difficulties and feelings of inadequacy as a student. The results showed that learning difficulties prospectively predicted depressive symptoms. Moreover, the impact of learning difficulties was mediated via inadequacy as a student: learning difficulties predicted feelings of inadequacy as a student which, in turn, contributed to greater increases in depressive symptoms. Finally, gender moderated the association between learning difficulties an…